Michael Schuenke Erik Schulte Udo Schumacher Consulting t ctitors
Lawrence M. Ross Edward D. Lamperti Etha n Taub lllustr.u ions l>y
Markus Voll KariWesker
I
Thieme
Head and Neuroanatomy
THIEME Atlas of Anatomy Consulting Editors
Lawrence M. Ross, M.D., Ph.D., Department of Neurobiology and Anatomy University of Texas Medical School at Houston
Edward D. Lamperti, Ph.D., Immune Disease Institute and Harvard Medical School
Ethan Taub, M.D. Neurosurgery Department University Hospital, Basel
Authors
Michael Schuenke, M.D., Ph.D., Institute of Anatomy Christian Albrecht University Kiel
Erik Schulte, M.D., Department of Anatomy and Cell Biology johannes Gutenberg University
Udo Schumacher, M.D., FRCPath, CBiol, FIBiol, DSc, Institute of Anatomy II: Experimental Morphology Center for Experimental Medicine University Medical Center Hamburg-Eppendorf
In collaboration with Juergen Rude Illustrations by
l.ibraryofCongress CDIXlloging-in-Publication Dam is available from the publisher.
This book is an authorized and revised translation of the German edition published and copyrighted 2006 by Georg Thieme Verlag, Stuttgart, Germany. Title of the German edition: Schuenke et al.: Kopf und Neuroanatomie: Prometheus Lernatlas der Anatomie.
Illustrators Markus Voll, Fiirstenfeldbruck, Germany; Karl Wesker, Berlin, Germany (homepage: www.karlwesker.de) Translator TerryTelger, Fort Worth, Texas, USA
Important note: Medicine is an ever-changing science undergoing continual development. Research and clinical experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowleclge at the time of production of the book. Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user Is requested to Hilmlne carefully the manufacturer's leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule oreveryform of application used is entirely at the user's own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page.
C corrected reprint 2010
Georg Thieme Verlag Riidigerstra8e 14 D-70469 Stuttgart Germany http:ffwww.thleme.de Thieme New York, 333 Seventh Avenue, New York, NY 10001, USA http:ffwww.thleme.com Typesetting byweyhlng digital, Ostflldern-Kemnat Printed In China by Everbest Printing Ltd, HongKong
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Softcover
ISBN 978-1-60406-290-8 Handcover ISBN 978-1 -60406-296-0
Some of the product names, patents, and registered designs referred to In this book are In fact registered trademarks or proprietary names even though specific reference to this fact Is not always made In the text. Therefore, the appearance of a name without designation as proprietary Is not to be construed as a representation by the publisher that It Is In the public domain. This book, Including all parts thereof, Is legally protected by copyright. Any use, exploitation, or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, Is Illegal and liable to prosecution. This applies In particular to photostat reproduction, copying, mimeographing, preparation of microfilms, and electronic data processing and storage.
1234S6
Foreword
Preface
Our enthusiasm for tile THIEME Atlas of Anatomy began when each of us, Independently, saw preliminary material from thlsAtlas. We were Immediately captivated by the new approach, the conceptual organization, and by tile stunning quality and detail of the images of the Atlas. We were delighted when the editors at Thieme offered us the appertunlty to cooperate with them In making this outstanding resource available to our students and colleagues In North America.
As it started planning this Atlas, the publisher sought aut the opinions and needs of students and lecturers In both the United States and Europe. The goal was to find out what the "ideal" atlas of anatomy should be-ideal far students wanting to learn from the atlas, master the extensive amounts of Information while on a busy class schedule, and, In the process, acquire sound, up-to-date knowledge. The result of this work Is this Atlas. The THIEME Atlas of Anatomy, unlike mast other atlases, Is a comprehensive educational tool that combines illustrations with explanatory text and summarizing tables, Introducing clinical applications throughout, and presenting anatomical concepts In a step-by-step sequence that allows for the Integration of both systemby-system and topographical views.
As consulting editors we were asked to review, for accuracy, tile English edition of the THIEME Atlas of Anatomy. Our work Involved a conversion of nomenclature to terms In common usage and some organizational changes to reflect pedagogical approaches in anatomy programs In North America. In all of this, we have tried diligently to remain faithful to the Intentions and Insights of the original authors. We would like to thank the team at Thieme Medical Publishers who worked with us. Heartfelt thanks go firtst to Kelly Wright, Developmental Editor, and Cathrin E. Schulz, M.D., Executive Editor, for her assistance and checking and correcting our work and for their constant encouragement and availability. We are also grateful to Bridget Queenan, Developmental Editor, who provided a uniquely thorough, thoughtful, and cooperatiVI! approach from tile moment she entered the process in the editing of this volume. We would also like to extend our heartfelt thanks to Stefanie Langner, Production Manager, for preparing this volume with care and speed. lawrence M. Ross, Edward D. lamperti EthanTaub
Since tile THIEME Atlas of Anatomy Is based on a fresh approach to the underlying subject matter itself, it was necessary to create for it an entirely new set of illustration5-il task that took eight years. Our goal was to provide illustrations that would compellingly demonstrate anatomical relations and concepts, revealing the underlying simplicity of the logic and order of human anatomy without sacrificing detail or aesthetics. With the THIEME Atlas of Anatomy, it was our intention to create an atlas tllat would guide students in their initial study of anatomy, stimulate their enthusiasm for this intriguing and vitally important subject, and provide a reliable reference for experienced students and professionals alike.
"Ifyou wunt to atmin the possible, you must otrempt the impossible" (Rabindranath Tagore). Michael Schunke, Erik Schulte, Udo Schumacher, Martkus Voll, and Karl Wesker
Acknowledgments
First we wish tD thank our families. This atlas is dedicated tD them. We also thank Prof. Reinhard Gossrau, M.D., for his critical comments and suggestions. We are grateful to several colleagues who rendered valuable help In proofreading: Mrs. Gabriele Schunke, Jakob Fay, M.D., Ms. Claudia Ducker, Ms. Slmln R.assoull, Ms. Heinke Teichmann, and Ms. Sylvia Zllles. We are also grateful to Dr. julia )Orns-Kuhnke for helping with the figure labels. We extend special thanks tD Stephanie Gay and Bert Sender, who composed the layouts. Their ability tD arrange the text and Illustrations on facing pages for maximum clarity has contributed greatly to the quality of the Atlas. We particularly acknowledge the efforts of those who handled this project on the publishing side: Jurgen Luthje, M.D., Ph.D., executive editor at Thieme Medical Publishers, has "made the impossible possible." He not only reconciled the wishes of the authors and artists with the demands of reality but also managed to keep a team of five people working together for years on a project whose goal was known to us from the beginning but whose full dimensions we came to appreciate only over time. He is deserving of our most sincere and heartfelt thanks. Sabine Bartl, developmental editor, became a touchstone for the authors in the best sense of the word. She was able to determine whether a beginning student, and thus one who is not (yet) a professional, could clearly appreciate the logic of the presentation. The authors are indebted to her.
We are grateful tD Antje Buhl, who was therefrom the beginning as project assistant, working "behind the scenes• on numerous tasks such as repeated proofreading and helping tD arrange the figure labels. We owe a great dept of thanks to Martin Spencker, Managing Director of Educational Publications at Thieme, especially tD his ability to make quick and unconventional decisions when dealing with problems and uncertainties. His openness to all the concerns of the authors and artIsts established conditions for a cooperative partnership. Without exception, our collaboration with the entire staff at Thieme Medical Publishers was consistently pleasant and cordial. Unfortunately we do not have room to list everyone who helped In the publication of this atlas, and we must limit our acknowledgments to a few colleagues who made a particularly notable contribution: Rainer Zepf and Martin Waletzko for support in all technical matters; Susanne TochtermannWenzel and Manfred Lehnert, representing all those who were involved in the production of the book; Almut Leopold for the Index; Marie-Luise Kurschner and her team for creating the cover design; to Birgit Car1sen and Anne DObler, representing all those who handled marketing, sales, and promotion. The Authors
lntroducUon to Neuroanatomy 1.1 1.2 1.3 1.4 1.5 1.6 1.7
Central Nervous System (CNS) ...•.....•....••....•... Neurons •.....•..........•....•....•.....•.....•... Neuroglia and Myelination .•....•..........••....•... Sensory Input, Perception and Qualities .•....••....•... Peripheral and Central Nervous Systems •....••....•... Nervous System, Development ..•.....•....••....•... Brain, Macroscopic Organization .•.....•....••....•...
172 174 176 178 180 182 184
2
Meninges of the Brain and Spinal Cord
2.1 2.2 2.3
Brain and Meninges in situ .•....•..........••....•... 186 Meninges and Dural Septa .•....•..........••....•... 188 Meninges of the Brain and Spinal Cord ..•....••....•... 190
3
Ventricular System and Cerebrospinal Fluid
3.1 3.2 3.3
Ventricular System, Overview ...•..........••....•... 192 Cerebrospinal Fluid, Circulation and Cisterns..••....•... 194 Circumventricular Organs and Tissue Barriers in the Brain 196
4
Telencephalon (Cerebrum)
4.1 4.2 4.3 4.4 4.5 4.6
Telencephalon, Development and External Structure •... 198 Cerebral Cortex, Histological Structure and Functional Organization •..........•....•..........•.....•... 200 Neocortex, Cortical Areas ..•....•..........•.....•... 202 Allocortex, Overview .•....•....•..........•.....•... 204 Allocortex: Hippocampus and Amygdala •....••....•... 206 Telencephalon: White Matter and Basal Ganglia •....•... 208
Cerebellum, External Structure ....................... Cerebellum, Internal Structure•.....•....••....•....•. Cerebellar Peduncles and Tracts ...................... Cerebellum, Simplified Functional Anatomy and Lesions .
8
Blood Vessels of the Brain
8.1 8.2 8.3 8.4 8.5 8.6 8. 7 8.8 8.9 8.1 0
Arteries of the Brain: Blood Supply and the Circle of Willis Arteries of the Cerebrum ............................ Arteries of the Cerebrum, Distribution •...••....•....•. Arteries of the Brainstem and Cerebellum .••....•....•. Dural Sinuses, Overview ............................. Dural Sinuses: Tributaries and Accessory Draining Vessels Veins of the Brain: Superficial and Deep Veins ....•....•. Veins of the Brainstem and Cerebellum: Deep Veins ...•. Blood Vessels of the Brain: Intracranial Hemormage ...•. Blood Vessels of the Brain: Cerebrovascular Disease ....•.
238 240 242 244
246 248 250 252 254 256 258 260 262 264
9
Spinal Cord
9.1 9.2 9.3 9.4 9.5 9.6
Spinal Cord, Segmental Organization •....••....•....•. Spinal Cord, Organization of Spinal Cord Segments ....•. Spinal Cord: Internal DlvlslonsoftheGrayMatter........ Spinal Cord: Reflex Arcs and Intrinsic Orcults ........... Ascending Tracts of the Spinal Cord: Spinothalamic Tracts Ascending Tracts of the Spinal Cord: Fasciculus gracilis and Fasdculuscuneatus ............................
9. 7
Ascending Tracts of the Spinal Cord: Spinocerebellar Tracts............................................ 278 Descending Tracts of the Spinal Cord: Pryamldal (Corticospinal) Tracts .............................. 280
Sympathetic and Parasympathetic Nervous Systems, Organization .........•....•................•.... 316
11.2
Autonomic Nervous System, Actions and Regulation ••• 318
11.3
Parasympathetic Nervous System, Overview and
12.12 Lesions of the Brachial Plexus ....................... 348 12.13 Lesions of the Lumbrosacral Plexus ....•..........•.. 350 12.14 Lesions of the Spinal Cord and Peripheral Nerves: Sensory Deficits ..••....•.....•....•....•.....•.. 352 12.1 5 Lesions of the Spinal Cord and Peripheral Nerves: Motor Deficits •...••....•.....•....•....•.....•.. 354
Ear and Vestibular Apparatus ..... .... ... ........ 140
10
Sectional Anatomy ofthe Head ...... ........... 156
Head - - 1. CmtifJI Bones
1.1
Skull, Lateral View
SqU~~T~CUS suture
Nubone
lnfrliGrllltll - -'?!.----'"\ foramen
A latil!ral'llfewoftflukull(cnnlum} Left later.al view. This view was seledl!d as an introducti~:~n to the skull because It displays tfle gre
2
follow. This unit rellfews the prfndp.al rtructures of the lateral aspect of the skull. The chapter as a whole is intended tD familiarizl! the reader wlth the names fAtheaanlal bones before proceeding to finer ~Ntomi cal detills and the relationships of the bones to one another. The teeth .ilre descrfbed In .il Sl!parm unit (see p.l6fl).
Head - - I. OVnJGI Bones
Tempor.ll bene, squamous part
P;u!etll bene
Mlndble
I l.atief.JIIIfewof the cr.Dill bones Left lateral VIew. The bones are shown In different colors to demonstrate more de.-.rly theirextef'lts and boundaries.
C Bona of the neurocnnlum (lri!Y) and vlsa!rocr.lnlum (or.mge) Left I.Jte!'al VIew. The skull form sa bony capsuleUlat encloses the brain, sensory organs, and viscera of the head. The greab!r size of the neu~ cr.ilnlum (cr.ilnlal \'iult) relillive to tfle Vlsarocranlum (fadal skeleton) Is a typiC.ill pdmate fu.rture directly correlated 'With the larger pr1mare brain. E Bones of the neurocnntum ;md llfscerocr;~ntum Newac111nlum (gray)
Vlsceroa-anlum (or•ge)
• Flontal bone • Sphenoid bone (excluding the
• Nasal bone • l.aalmalbane • Ethmoid bone (excluding the alblfronn plate) • Sphenoid bone (pterygoid process) • Milllllla • Zygomatlc bone • Temporal bone (tympanic part, styloid proceM) • M~ndlble • Vomer • Inferior n.asal turbil\lte • P<~lallne bone • ~ld bone(seep.31)
pt«ygold proeMS)
•
Tempor~lbone
(squ..mous part. petrouspart) • Parld31 bone • Ocdpltal bone • Ethmoid bone (albrtronn plm)
D Os:sffk:iltlan of thecr;~nt;~t bones Left tater.ill VIew. The bones of the sla.ill either dewlop directly from mesenchymal ronnective tissue QntramembraAOUS assification, gr.ty} or form Indirectly by the osslflC
F Bones of the desmiKT.Inlum .1nd chondrocr.mlum Chonllhcl'llnlum (blue)
• • • • •
• • • • •
Nasal bone Laaimalbane Maxilla Mandible Zygomatic bone Frontal bone Parietal bone Ocdpltal bone (upper ~rt ol the squama) Tempor~l bone (squ..mous part, tym~nlc part) P;~laane bone
• Ethmoid bone • Sphenoid bone (-luding the medial plm ofthe plli!\'Wald proeMS) • Temporal bone (petrous and mastoid parts, styloid process)
• Ocdpltal bone (excluding the upper part of the squama) • Inferior nas.1l turblnite • Hyoid bane(seep.31)
• Vomer
3
Head-- 1. CmtifJIBones
1.2
Skull, Anterior View
FIOOt
P
S~,J~n~orllltal
foramen
m~rgln
NIL'wllbone
Sphl!flOidbone. greab!rwng
Sphenald bone, lesser wing
Temporal bene
Orfllt
Eitlmaldbone, pe~pendlcular
plm
Sphl!flOidbone. greab!rwng
lnfraorbltll
Zygomatic: bone
""'111'"
Plrffonn (anterfar
t.'lckleoi5011 llCH'ICha
1'111111) lperWn!
Max! I~
Vomer
A At*rforvJewoftheskull The boundaries of ttle facial skeleton (vlsc:erocr;mlum) can be dearly appr«lilted In ttllslllew (the lndMdual bones are shown In B). Tbe bony margins of ttle ant:erior nas.1l aperrure mark the start of the respiratory
tractlnttleskull. The nasal cavlty,llkettleorblts,cont
4
(the olfactory mucosa). The poru,_l slnllm a~ shown schematically In c. The anterior view of ttle skull also displays the lhree clinically Important openings through which sensory nerves pass to supply the face:
the supraorbital foramen, infraorbital foramen, and mental fDramen
(see pp. nand 93).
Head - - J. CranlaiBones
c===
~FIVnbllslnu•
- Ibon.• P:lrlotll bon~ sphe.n old...__ .~\ling
Notal bon~
Temporal bane
Mlddu...t condlll
Sphenoid bone.
lnfe1ornallf
l)gomrdc bon~
g~Yoing
sphenoid nua
~ MDIIlaryslnus
i'Msal~
MDIIla
~I
pllor ~--
Yertlaol --~~'I
:..::::;;;
Ethmoldool.ls
c ...r.naulslnuses: pneurnMizniOn nghtretts the bone AntErior view. Some of the bones of the fadal skeleton are pneumatized, I.e., they contain al~lled cavities that reduce the tntal weight of the bone. These cavlttes, c.alled the p;tr.masal sinuses, commu nlcate with the niiSoill cavity and, like It, ire llned by Clllltll!d respiratory epithelium. lnflamrNtions of the pal"iinia.il sinuses (sinusitis) and assodmd complaints are very common. Because some of the pain of Jlnusltls Is projected to the skin overlying the sinuses, It Is helpful to know the proJections of the slnu:ses onto the surface ofthe skull.
Horllantll >ygornotlc pilar
~millie
pillar
•
II
Horimntol ZV!!Omlllc pillar
D Prbdptllnes of fora (blue) In the flclilllbleton Anterior view, b ~ten! view. The pneumatized paraNsal sinuses (C) have a mechanical counterp;art in the thickened bony "pollars• ofthe facl
11
E LeFort dilalfleiltlon Ill mldf.S.I hdUI't$ The frame-llke construction of the fadal skeleton leads tD characteristic p;~ttems of fracture lines In the mldfaclal region (LeFort 1,11, and Ill). LeFort I: This fracture line runs icrvss the maxilla and ab~M: the hard p;tlate. The maxllli Is 5eparited from the upper ficlal skeleton, disrupting the integrity ofthe maxillary sinus (low 111mswrse(rudure). LeFort II: The fricture line passes across the niiSoill root. ethmoid bone, maxilla, and Z)'!IOrllitlc bone, creating a pyramid frudu~ that disrupts the in~grity of the orbit. LeFart Ill: Thefidal skeleton Is sep;t rmd frvm the base of the skulL The main fricture line p;~sses through the omits, and the fricture rNY addltloNIIy Involve the ethmoid bones, fronul sinuses, sphenoid slnu:ses, and zygomatic bones.
A Posterfonfew of U!e skull Tbe ocdplt.ill bone, which Is dominant In this view, articulates With the p.arietal bones, to which it is mnnected by the lambdoid subJre. The mnlal suwres are a special type ofsyndnmoJis (•llgammtouJ att.ilch·
6
ments that ossify with age, see F). The ower surface of the ocdplt.ill bone Is contoured by musaJiar origins and Insertions: the lnfertor, superior, arld supreme nuchalline.s.
Head - - I. OVnJGI Bones
Temporal bent. squamous p;rt Tempon~l bent.
petrQwp;rt
D C'nlnllll deformltfts due to the prerNQI~ dosu~ of cranllll sutures The premature dosure of a aanlal suture (craniosynostosis) may lead to characteristic cranial deformities. The foii0Wif19 sutures may close prematurely, resulting in various cranial shapes:
8 Postelionfew oftfle cnnlill bonts Notr: Tbe temporal bone consists oftwo ma1r1 parts based on Its embry· 011ic development: a squamous part arid a peb'Dus part(see p. 22).
a S.agitbl suture: scaphocephaly (long, narrow slwll) b Co~l suture: oxycephaly (pointed skuiO c Frontlll suture: trigonocephaly (triangular skull) d Asymmetrlcill suture closure, usually ln~ng the coronal suture: plagiocephaly (asymmetrical skuiO
Ant.!r!or -----,-...:~
fontlnele
-
PosWior
fon!anelle Llmbclold
suture
•
• E HydroGI!flhillus ;mel mlcnocepflaly suture Coronal suture
- "'""'=- ---1
b
C 111e nll!llniltiillslalll • 1St later~! view, II supenor lllew. Tbe flat cranial bones mlllt grow as the brain expi!nds, and so the su· t:ures betwemthem mustremalr1open forsometime(see F). In the neo· nate. there are areas betweer1 the stlll-growlr~g cranial bones that are notoccupledbybone:tbefonunelles. Theycloseatdlfferenttimts(the sphenoid fontllnelle in about the 6th month of lif\!, the mastoid fonta· nellelnthe 18th month, theantalorfor~tanellelnthe 36th month). The postvtor{ont!IMI/e provides a refa'ence point for describing the position of the fetal head during childbirth,
• Characterfstfc cranlalmolllhology In hydroCfll/Hllus. When the brain becomes dilated due to cerebrDSpinal fluid accumulation M{rw the cranial sutures O$Sify (hydrocephalus. "water on the brain"), the neunoaanlum wlll expand while the facial skeletor1 remains unchar~ged. b Mlcroa!phalyresults from premature closure of the cr
F AIJut which tfle prfrtdpal sutures ossify Suture
••-lftatlon
frantill suture
Childhood
Saglttll suture
20-JOyears of age 30-40ye.arsohge 40-SOyears of .age
Con10al suture
umbdold suture
7
Head -
1.4
T. CrtlniGI Iones
Exterior and Interior of the Calvaria
Fruntll bane
Fruntll sl.....
O.:dpltll bGne
A !Extl=rfllf (•) •ncllnterfDr (b) Gfthe u1Rrf1 The extemil surface of the alvarla (•) Is relaUvely smoodl, unlike Its lntamal surfiCI!! (b). It Is defined by the fronbl, JHrletal, ind ocdpltal bones. whic:h are intercon~ by the CD~Uni!l, Jll!littill, and lambdoid sutures. The Jmooth external surface Is Interrupted by the ~rietal foramen, whlc:h giYeS JHSSage to the JNrfetal emls.sary win (see F). The lntemi IsurfaCI! Df the Ciilvarla also bean a number Df plts and gro~MeS: • The granui.Jr foveolae (smill pits In the Inner surface Df the skull caused by sacrular protrusions Dfthe arachnold membrane ~ng
the brain) • The groove for the superior sagittal sinus (a dural voenous sinus Dfthe
brain, see Fand p. 65)
G........ rw s._tor ygttol sha
PllrleUI fwamen
• The arter1al groavu (which mark the positions Df th.e arter1al wssels af the dura mat«, such as the middle meningeal artery which supplies most of the dura miter and tMriylng b11ne) • The frontal aest (which gives Olttachmentto the fabtCI!Rbrl,a sickleshaped fold Df du ri miter between the cerebral hemispheres, see p. 188).
The frontal sinus In the frontal bone Is also visible In the Interior YII!!W.
8
Head - - J. CranlaiBones
FrollUI -~---: bone
P..-1 bone
r: lh! salp and miVIIrtll Note the three-l;oyered strurnl'l! of the calvaria, consisting of the outer table, the dlploi!, and the Inner table.
B Extertor ol the miVIIrtll viewed trom llbGft
The dlploi! hu a spongy struct\lre and conulns red (blood-forming) bone man-. With a phasmacytorn;~ (malignant transformation of t8'taln white blood cells), nna ny srn;~ll nests of rumor cells may destroy the suft'Dunding bony trabeculae, and radiographs will demonstr.rte multiple lucent areas ("pcmched~ lesiO!U") In the skull. Vessels called m~ lssrlry wins may pass through the calvaria to connect the w.nous sinuses of the bl"iiin with the wins of the scalp (see panels E
D Se111111¥1tyvfthe lnner&lble tD tnum1
SUperfor
The Inner uble of the c.Jtvarlals wry sensitive to extm!al tnuma ;md may fracture - n wh~ the outer table teT~ains intact (look for correspcmdlng e¥1dence on CT Images).
HlltQIStllll
I
r ~1=____---r ==of
n-........... --::-~____: "r.:f-.:.0.,:::-+- -rkr
sinus
- k=-"'-"'-"---'-=-.,---- Ocdp~l
temporal
emlssllyvdn ~Po"+- Mos!Did
dlplolcwln
emllsorywln
Oa:~l
L.,.l~~---
dlplalcwln
a.nd)iar emllsorywln
External -~~+---'11~~
wrtS>ral wnaus plaus E Dlplok wlnsln the alvlrtl
F Emissary w1111 af the ocCiput
The diploic wins are loc.Jted In the cancellous or spongy tissue of the cranial bones (the dlplol) and are visible when the outer table Is remowd. The diploic winJ communicab! with the dur~l-us .sinuses and seal p wJns by w-.y of the emissary w:lns, whim autr a potential route for the spread of Infection.
Emissary w:lns establish 1 direct con nectlon between the dul"iil venous sinuses and the extruril nl;ll wins. They p.liSS through pn!formed CTillnlill openings such 01$ the parietal foramen and mastoid foramen, The enliss;ny veins are of cllnlc.JIInterest because IIIey may allow b.ictrrli from the scalp to enter the skull along these w.lni and Infect the dUl'il mmr, causln51 menlnStltis.
9
Hftld -
1.5
'· Cranlol Bones
Base of the Skull, External View
~·bone
~""nebont
fronalbone
lnfsiornaAI mnch•
.51Wnold bone
vomer
Tl!fT'4XIralbone, zygomallc pro«$$ T'tfl'9aral bone, fqUIITIOUJ part Tl!fT'4XItilbone, tyn'4)1nlc part fl!fT'4XI18Ibone, petrcus Pll't. mastDidp.1rt
Foramen INgl&m
Oo:lpllal bone
A Iones of tfle bae ofIitie llkvl lnfelforvtew. The bue oft11e 51rullls composed of a mosak-llk.e assembly of v~rious bones. It is helpful tD review the shape and location of
these bona before studying further details.
tolldele cranlolr-.
:;.:...._ _ _ _ _ CMalld
canal
B lb!laUonshlp of the fvnm~~~lamrum ta tfle Arotld C3Nil and lnternlll carotid •rtery Left lateral view. The for1men lacerum is not a true apature, being occluded In life by a 1aytr of fibrocartilage; 1t appears illS an opening only in the dried slwll. The foramen l~cen.m is dosely related tD the carotid c;mal and tD the Internal carotid artery tiNt travenes the canal. The gIHII!r petrosal nerve and deep petrosill nerve ~s 111 rough the foramen laten~m (see pp, 81, 85, and 90).
C The~lllhapectoftheskul lnfertorvlew. The principal extemal features of the biseofthe skull are labeled. Notl! particularly the openings that transmit ne!'VI!S and Ye$· sels. With abnormalities of bone growth, these Ol)enings may remain too small or may become nal'!'lliWed, compressing the neui'O'r.lsaJiar
structures that pass through than. Ifthe optic canal falls to grow normally, It may compress and damage the optic nerve, re.51JII1ng In visual fleld defeds. The symptoms associated With these lesions depend on the affected opening. All d the sll'uctlJres dl!pidl!d here will be mnsi~ ered In more det
11
Head-- 1. CmtifJIBones
Base of the Skull, Internal View
1.6
Jugum
---'~-----...
sphenolclale ·IO"!~:IfP'-._..
- - - Temporal bone, squamous part
.aiiiiiio....-'- - LHser...tngof
~naldbone
' Foramen
---Middle
cranial~
____:~~~
~..,
~tlor ---"::+-......:.,~-
CI\lnlalf(ISgo
• A BoM!iofthe baseoftheslaJII,IrrtHnalvTew Diffi!tef'lt colon are used here to highlight the arrangement of bones in
Middle cn~nlalfll556
the biiSe of the skull as seen from within the cranium.
F~~n~ --~~~~~~~~ pillar
"pillar
tr.II\SWI'Se --~~-
l'tBygald - --.l,__.l.L.....,.¥.'1 plllr
Vl!l'tlal zygcm.Jtlc pillar
Posb!r!or mnlalfossa
l'cnlmen
b
. ..-r;~r-~mn~
m1!J1Lm
zygomatic:
pillar
B
TMcnnlllfosne
a lntl!rlorlllew, b mldsaglttal section. The l'ntei'Jorofthe 5kull base~ not ~~+-~ot tr.III$\OeiSe
pillar
fl~t but is ~ w form three sua:essille fossae: the anterior, m~ die, and posterior a.-anlal fossae. Thesedeprenlons become progruslvely deeper In the frontill·tx>occlpttal direction, forming a terraced arranger menttllat ~displayed most dealiy In b. Thecranial f\ns~ are bounded bythefoi!Qwing structure$:
• Anterior to middle: the le$Ser wing5 of the sphenoid bone and the jugum sphenoldale. • Middle to posterior. !he superior border(rfdge) oftile petrous part of the temporal bone and the donum sellae.
c Bale ofdie skull: prf!Mfpalllnes of~ and _.,..mDII fl'ldllre lines a
Prlnclp;~lllnes of force, b common fr.-acture lines (Interior views). In response to masticatory pressures
clp;alllnes of force (comp;1re with the force d!str1but!or1in the anterior view or1 p. 5). The Intervening areas that are not thickened are sites of predl!ectlor1 for bone fradllres, resullfng In the typical pilttems of basal skull fracture lines shown hen!. An analogous phenomenar1 af typic.al fracture lines I~ found In the mldfadal reglor1 (see the anterior views of Lefort fractures or1 p. 5).
D lrrtmarof the baR ofthulcull It is interl!sting tD ccmp;~l'l! the openings ill the interiar of the base of the skull with the openings visible In the external vlew(see p.11 ). These openings do not alwiys colndde bec:.1use some neurova1cular struc· tures change direction when passing throcJgh the bor~e or pursue a rela· tively long intr.lo$Seous course. An example of this is the inb!rn~l acous· tic meatus. through which the facial ne~W.. aiTIOilg other structures. p;~sses from the Interior of the skull Into the petroU5 part of the tenn· por.al bone. Most of Its ftbers then leave the petrous bone through the stylom;moid for~men, which is visible from the external ~pect (see pp. 80, 91. and 149 for further details). In learning the sites 'Where neurovascular structures pass through the base of the skull, It Is helpfullnltlally tD nat2 whether these sltl!l are
located In the anterior, middle. or postenor cranial fossa. The .mangement of the crallial fossae is .shown ill B. The cribriform plate of the ethmoid bone connects the nasal cavity with the anterior cranial fossa and Is pertor.~ted by numerous forimlni for the p;~ssage of the olf.lctoryfl. bers(seep.116). No«!: Bec:.1use the bone is so thin in this~~.~ frontal head injury may easllyfracturetheafbr1form plateandlacer.~tetheduri mater. allowing cerebrosplnil fluid to enter the nose. This poses a risk of meningitis, as bactena from the nanstenle n.u.al CON!ty may enter the sterile cerebrospinal fluid.
13
Head-- 1. CmtifJIBones
1.7
Orbit: Bones and Openings for Neurovascular Structures
8 OpenlnSJI In the ortlltfor neui'VIIiii5Cular structures Nfl~: The supraorbital foramen is an important
site In rvutfne clinical examinations because the examiner presses on the supraorbltll rfm wtth the thumb to te.st the sensory function of the supraorbital nerve. The supraomitll nerve Is a terminal branch of the fll'lt dlvlslon of the trfgemlnal nerve (CN V1• seep. 76). When paln Is present In the dlstrlbutron of the trtgemlnal nei'Vt', tCS'Idemm to pre$SUre may be n~ted ;at the supr.1orbltill site. Open... or
....... Optic: canal
• Optic nel'lllt (CN II) • Ophthalmic arterr
Superfor orbltill
• Oculomotor nerve (CN Ill) • ~chlear neM (CN IV) • Ophthalmic neM (CN V1)
foramen A Bones of the rtght orbit Anterior vlew (•). later.~l view (b), and medial view (c). The lilta"al orbltill w.~ll has be\!!\ 1'1!1Yloved In b, and the medial orbital wall has
beftl1'1!1Yllllll!!din.:. The orblt Is formed by seven different bones (tndic.rt:ed here by color shading): the frontill boDe,. zygomatic bone. maxilla, ethmoid bone,
14
sphenoid b~ne (see a and c}. and als~the lacrimal bone and palatine bone, wfllc:h are visible only In the medial view (see b). The present unit deak with the bony anatomy of the orbits themselve$. The relationships of lfle orbits t» each 01fler are described In the next unit.
Posterior ectlmald~l
foramen
• Pom!rlorethmold;al artery, weln, and nerve
Head - - I. OVnJGI Bones
FnxrtllllndS\U't' S~.pr.~arflltll-
ilr.amen
Postufar et!lmoklal fcr.amen
Frant.11bone. cdlltllpart
Antl!rfar el!lmoklal fcr.amen
2MiamllkD-
Optic anal
orblbllfar.~men
1\lmlbone
Supe!or cdlltll l'lsiure
MildIIa. fro lUI p!'OO!S $
Z)'gOmatlc
bone lnfl!rfor cdlltll fissure
lolafmal bon~ Ethmoid bone. adlltll plate
lnfraarflltll
9'0Madia, Clbltll surfaa!
lnfraorbltll foramen
Antl!flor lia!m11 am(lllilldl•l
ahmoklbone Optic c;anal
~qf llcrl~lsac
(I'Alttopenlng forl\iiiOiia!~l
Glct)
._.,
.#t
Frantol bone. arfllt.ol suoiact'
b
c
lnfetfar adlltll ftssu re
Openl'nglln the right orfllt for nl!llrovruaJiarstructiJres
Anterior view (a), lateral view (b), and medial view (c). The lateral orblt.ll w.~ll has been remcwed In b, the medial orbital w.rll In c. The followIng opa1lngs for the pass.1ge of neuF'O'r.l1aJiar structures (see listing In B) can be ldernlfted: the supenor and lnfl!dor ortllt.ll flssures (a-c), the optic canal (a, b), the anterior and posterior ethmoidal foramina (b, c), the Jllf'raorbttal g~WVe (<~),the lnfraortllt.ll canal (b, c;), and the lnfr.rorblt.ll foramen (011, b). Dlillgram b shows the or!flce of the nasolacrimal duct. by which lacrfmal fluid is conveyed to the inh!rior muW$ of the noM!. The lateral view (b) demonstrates the funnel·llke structure of the orbit. which funcUons like a socketm cont.lln the eyeball and constrain Its mOIII!rnents. The lnh!rtor ortlltal flssure operu Into the ptzrygopalaUne fossa, which bonders on the pDS!J!riarwall of lfle maxillary sinus. It contorIns the pmygopalatine ganglion. an lmpoltlnt component of the parasympathetic nervo~~S system (see pp.81, 101). The upper part of the exposed maxJIJary sinus bears the o.suum (In the milldllary hiatus) by which the sinus opens into lfle nas.al cavity superior to lfle inh!ri~:~r concha (see pp. 2o-21 ).
15
Hftld- '· Cnmlollones
1.8 Orbit and Neighboring Structures
1 Olnlcally lmpclfUllt relltlonlhi.Hc..n the orllltland sumaundlng
A BaMs crf thnrttltnnd ed)lftllt cavtt1111 The color-coding here b the ~me liS for the bones of the orbit on pp.14-1 5. 'These bones also fonn portions of the Willis of neighborin11 ciiVIUes. The following ldjicent structures are visible In the diagram:
Disease processes may originate In the orbit ~ nd spread to these cavities, or orlg lnm In these C
• Pltulblry
• c-mousslnus • l'tt"''!!opliltlne fossa
• The Rrminologio AnolomiaJ NS drapped
the term 'ethmoid sinus' In filvor of 'eth· mold cells..'
otsto
Flollbl bGne. ertobl surfm!
golll
Spllenald bc!N., '-'twlllg Elhmold bone.
OpllcCIJiill
pe~p~ndlallor
plllle El!lmolclbon~
ort.IUI ...
s~
arbltMftmn
(lornln• PiP\'riiCN)
Sl4)011or ,_la>ntm
Orblbolsurlloz. gutrwtlg
Zygomotlc: bone. ariolt:.I!Oirliu:e
lnflftar orblt.l ftssure
lnlriortitil
OrtiiQift-
aMI
Middle naiGDn!N
Mildlory
sinus Polatlne
pnxmofthe I!Midli
C Ortolb ilnd1Wighboftn1 ltnldllnll
Coronal sect1on through both orbits, * - d from the front. The walls sepuatlng the orbit from the ethmoid c:ells (o.3 mm.lamlna papyr.~ceii) .-.nd from the mMIIII ry sinus (0.5 mm, orbital floor) are very thin. Thus. both of these walls are susapbble to li'actunl!s and providll! routes for
16
the spsnd of tumors .-.nd Inflam mltory processes Into or out of the orbit. 'The superior orbital fissure communlutll!s with the middle aanlal fossa. and so sevm~l stnlttures that are not pictured he~the sph~ nold sinus, pltulury g.land, and optic: c:hlas~re .-.lso c:JOM!y related tD theorbil
HeGtl - - I. OVnJGI Bones
l'fantalbane. zygomatic: procHS
Ethmoid
(i->Oing. tl!nlporalsurface
~
I
bane
Ternporal bane. squama ~a part
I
lnfu'lor Spheno-
SphtMpallnle
5quamau5 5ublre
~ma'l
~ p;~lltlne
foss;~
Maodlary
Seedet.111
tu!Mroslty
lnF
orfllt.1l
IIWJre Cho;na
Temporal surfaae
hlltfnebane. ~nmldal p!'OCHS
lnfratl!m· poralcn!rt
~d
Pl:efygold
proc:HS,
~
mecfal plate
lmral plate
Fanunen '!llnasum
l'terygald
hamulus
D CIOSHJp111tw oftfle left ptll!f)'gopalltlne llilsM Lareral view. The ptl!rygopalatlne fona Is a crossro;rds between the middle cranial fo~a. orbit. and nose, being travened by many nerves and vessels !flat SIJpply lhe.se s!JIIctures. The ptl!rygopalatlne fossa Is mntinuous later~lly with !he infratemporal fossa. This diagr~m shows the lareral appro;rch w the ptl!rygopalatlnemsa through the lnfr.ltem· poral fossa. wfllch Is utllrzed In surgkal operations on tumors In this re· glon (e.g., nasopharyngeal tlbroma).
l'llCIJndum
bone.
Fe ramen
~d
Grt>a12r - ----l palatl'lecanal
l'rom:
Middle cran~l fossa
•
Pteryogoid anal (Vldlan canal)
Skull base (Inferior surface)
• GreiltJer petn»al nerve (p;~rasymp;lthetic branch ofhcfal nerve) • Deep petno5lll nerve (sym()ilthetlc llben from carotid plexus) • Artleryofpteryogoidanal with accomp;~nylngvelns • NeNe of pterygoid anal
F ConnectSons of the left pWftllpalltlne llilsM wttfl1djacent ~
Detail from D. The content3 of the ptefygop;rlatlne fossa Include the pterygop;rliltlne ganglion (see pp. 81, 101), 'Which Is .m lmpoi'Unt
G'Jille
E Structures adj1u:enttD tfle l'l!llt ptl!ryg~~p~llltTne Inferior view. The arrvw lrldlcates the approach to the pterygopalittlne ~sa from the skull base. The fossa Itself (not visible In thlsvlew) Is lateral to !he lateral plate of !he ptefygold process of the sphenoid
l'tlell!loldpi'Oa$$ filelllendlcular plate of llle palatine bone lnfmemporal fossa {via the ptiefygomaldllaryfl.ssure) Ciremer >Oing of the sphenoid bone, junction
A SktletDnoftfleextemal nose I.J!ft lmral view. The skeleton of the nose is compDSed of bone, arti· lage, and connectfn tlssue.IU upper portion b bony and frequently ln· wived lr1 mldfidil fractures. while Its lower. distil portion Is cartlligl· nous ~nd therefore more elil!tlc ~nd less susapabletlllnjury. The proxl· mal lower portion af the naroils (alile) is compo$td of connective ti5sue with small embedded pieces qf cartllige. The lateral nasal cartilage Is a wlr~gnlce litl!ril expansion of the eirtllaglnous Nnl septum r.ttlterthan a sepi!rate piece of cartilage.
B N1111l urrJiage
lnferiarview. Viewed fn:lm belaw, e.achof the majoralarc.artilages is seen to consist af <1 medial and latEral crus. Thls view aiJO dl~plays the two nares, 'Which open lrlto !he Nsal CiiVltfes. The rfghtilrld left nasal cavities ane Sl!l)armd by tile nasal septum, whose Inferior cartilaginous port1or1 is just visible in thediilgram. Thew.rll structure afa single nilllal c;Mtywill be described In this ur11t. and the relatlonshlp of the nasal Cil\'ltytothe par<~Nsal sinuses wlll be explored lr1 the next unit
Elt1mold
bane
Sphenoid bane
Majoraar c.JI1lL11ge
Plllltfnebane
c
BonM of the llltmiiWllll aftfle rTght n.~~o~l cntty I.J!ft latl!ral view. The lateral wall of the right nasal cavity is fllrmed by
slx bones: the mi!XIIIa. nasal bone, ethmoid bor~e. Inferior nasal concha, Pilatlr~e bone. and sphenoid bone. Of the nasal concha. only the lnfe· rlor Is .a sep.;~r.ate bone; the middle .md superfor conchae are pi!rts ofthe ethmoid bone.
18
D Banes of tfle na~~l septum Parasagittal section. The nas.1l septum is fllrmed by tile following bones: the nanl bone (rwf af the septum). ethmoid bone, vomer. sphenoid bone. Pilatlr~e bor~e, and rNxllla. The latter three contribute only small bony pro}eciSons to the nasal septum.
HeGtl - - I. OVnJGI Bones
Antafor
Superior meatus
AM~r~l----~---~
apert!Jre
Pb!rygold PI'OCHS, mecllal plaiJ!
Inferior meatus
Middle concha (ethmoid bone)
E l.iltel'lll Willi ofthe rtght n..-.1 catty Medlallltew. Air enters the bony nas.1l avlty through the inteffor nas.1l aperture and travels th~gh the three nas.1l pass.ages: the supe!'for me-
it:Us, middle meitus, and Inferior meatus. Air le;rve:s the nose through the chOin<~e,. enterlng the nasopharynx. The three niSi I pasS<~ges ue separated Into meatuses by the lnfenor, middle, and superior conchae.
-----------Sphenoid ,(ni.IS
~mddbon~------~~----
pe~pendlalar pi~
.....:;;iiiii::"~--TriP:....;.;._,'----
Sphenoid
crest
Ma)or~lar
c.rillge,
medlalcna
F N111118lseptum
J>.arasagittal section viewed from the left side. The left lateral wall aftne nas.1l cavity has been removed with the adjacent bones. The nasal sep· tum canststs of ifl anterior car111aglfiOUS part,. the septal cartilage. ind a postl!rlor bony part (see D). The postl!rlor proceu of the car111aglno~
septumextendsdeeplfltothebonyseptum.DeYiatlonsofthenasilsepl:lJm are common and may irMIIve ttre cartilaginous partafttre septum, the bony part. or both. C..5eS In which the septal deviation Is sufficient to cause obstructlor1 of r~aS<~I breattrlng an be surgle<~lly corrected.
19
'· Cranlol Bones
Hftld -
1.10
Nose:
Paranasal Sinuses Fronul sinus
Mullllry sinus
•
b
ElhmGil Cl!lls
MM.IIory
Sphmd
nna
siNJS
A Projedkln of the J11111nlulllnuses oniD the skull • Anterior b lm:ral vi-. The paranilsal sinuses 1re alr-fllled CiYltles that reduce the weight of the skull. Because they ire subject to lnfl3mmltfon that may cause pain CMr the a!Rcted sinus (e.g.. frontal headiche due to frontal slnusltb), knowing the locltfon of the sinuses Is helpful In making the correct diagnosis.
vi-.
a Pni!UIIIt!HifDII rJI the mulllary •nd fnlnblthllel Anll:rior view. The front
Ant1:1tar cr.~ri•l'-•
Cutedge
Sclhonoil >ln~s ScJhonoPi'lallne fwimtn
----lt:=-- - Bodyof sphmd bane
u~~--~~--~----~~ pnxeB
Fronliol
Cutedg!Gtmlddlo n...J mncha {etlvnald bone)
C l..literal-11 rJI the right n...l ciiVIty Midline section vi~ from the lfft with the nilSal conchae~ moved to dlspl~ the openings of the ni1Sobicr1mal duct ;md parilliSill sinuses Into the nasal c.avtty (see colored arrows In It: red • NsolaalrN I
1, b
duct, ydlow • frvntal sinus, orange • mulllary sinus, green • antaior ilnd posterb ethmoid cells, blue- sphenoid sinus: drilfnage routes are destnbed in F).
20
b
Head - - I. OVnJGI Bones
frantll
OfK.a
Anterfar --__ cr.tnlalfosn
mur.
gall
,-_- --_
·~!-'·
Etllmold bone, artltal plm
(
'1---..___ ~ Olllumof
! _ ---r--_ mullloryslnus
r-_
~ ·
.J D Bo11111tn1ctur.ofthe INI~hlnuMJ Anterforvlew. The cen!r.llstructure of the patl!llOSG/ s.tnw:ts Is lfle elhmold bone (red). ItS cribriform pl;tte !Wms a portion of the anterior skull base. The frontal and maxlllaryslnuses are grouped around lfle ethmoid bone. The lnfe· rlor, mlddleand supe!'formeatuses an belden· tified within the niiS
NIMI
Inferior
Milldllorysnur.
P
II!;try sinus 05tlum Is the ethmoid bulla, ~h:h cont.11ns the middle etftmold cells. At Its iflte. rfor mll~ln Is a bony hook. lfle uncinate proa!$$, ~ich bounds tne mill011ary sinus ostium anteriorly. The middle concha Is a useful land· marie In surgle<~l procedures on the maxillary sln~a lind anterior elhmold. The lateral wall separ;rting the ethmoid bone from the orbit is the paper-thin orbital pl
E Nulll caMty lind plnlllnllnl strues
Transverse section viewed from above. The mucosal surface anii!Zimy has been left Intact to ~- ~~- narrow the nasal passages a~ Even relattvdy mild swelling of the mucosa may obstruct the nasal cavity, Impeding aeratlofl oflfle parana sal sinuses. This diill!lr;~m abo shows that the pituit.1ry gland, loc<1ted behind the sphenoid sinus In !he ll)pophyseal fossa (see C), Is il~slble to transnasal su~le<~l procedures.
fnx1tllslnus
F Sites wflere the nasoiMrlrNI duct and par~~~r-.JIIInuMJ optn Into die.._
section. Wilen the mucosa (dilated epithelium) lr1 lfle ethmoid cells (green) becomes swollen due to Inflammation (sinusitir.), it blades tfle flow of.secretions (see arnowl) from the front<~l slr~us (yellow) and maxillary sln~a (orange) In lfle ostlomeat<~l unit (red). Because of tflls blockage, mkroresplr.~tory
organisms also become trapped 1r11fle other sinuses, where lfley may incite an inflammallofl. Thus. while the anatomle<~l focus of the dlse<~se lies lr1 the etilmold cells,lnflammatory symptoms are also manlti!sted In the front.ll and maxillary sinLIIes. In patients with cl!ronic 5lnusltts, the narrow sites e<~n be surgle<~llywf~ ened to establish an effecUve drainage routr. !hereby curing lfle disease.
21
Hftld -
'· Cranlol Bones
1.11
Temporal Bone
A l'lllltlonofthetemlloralbone lnthesbll l.eftliltlerillvlew. Thetemporal bone Is a major component: of the base of the slcull ltfonns the capsule for the auditory and Witlbulilr .app.arilll:us and bnrs the articular fum of the temporomandibular joint. --"'='"""=--=~-Temporal
bono
,...
_......:;4--- tblldlbulilr - - - ------:F--- !iq........... part p;ort
-.. p;ort
Tymp;onk-........;~~~
p;ort
• B Olllflcdon cet*rs of the left temporal bone Left: latJeral vh:w, II Inferior view.
The mmpor.al bone develops from three cenll!rs thilll: fuse tD folm .a single bone:
• The petrous p.art. or petrous bone (paleglftl'l), contains the auditory and ~bular app.aratus. • Thetymp.anlc p.art (dariatr green) forms large porUons of the external iiUditDry canal.
• The sqUimous part. or temporal squlmil (light green), bears the articular foss.~ of the temporomilndlbular joint (ll\ilndlbular fusu).
Noll': The styluid pllllteSs appurs tD belong to the tymp.anlc part of the ll!mporal bone because of ItS location. Dewlopmentally, hDWeW!r, It Is
il
partvi the petrous bone.
Ounfil
tymp.onl
'l)rmpa-1k--~
""'mb.,ne Ph•ryng~rlc
(•udiiDry) tube
22
l'icl111 norve
Matdd olr Cll!ls
c Pro)edlan of dlnlc.ally fmporbnt ltluclures antD the left tllmponiiKin• The tymp.anlc membrane Is shown tnnsluamt In this lilll:er.al view. Because the petroU5 bone c:ontains the middle and inner ear and the tympanic membrane, a knowledge of Its anilll:omy Is of key Importance In otological surgery. The lntemil surface of the petrous bone hils openings (see D) for the panage of the filcii I nerve, inll!rnill carotid illt!:ry, ;md lnll!rnal jugulu vein. A nne nerve, the d1ordi tympani, passes through the tympanic amy, and lies medial tD the tymp.anic membrane. The chorda tympani artses from the facial nerve, which Is susceptible tD Injury d urtng surgical procedures (see C. p. 79). The mastoid pnKeSS of the petrous bone fonns air-filled cl1ambers, the mastoid cells, that vary gr5tly In size. Becau:~e these chambers c:ommunlcall!wlth the middle ear, which In tum c:ommu nlcatti wtth the n.asop~rynx viii the philryngotympanlc (au.dltDry) tu.be (al.so called Eustachlin tube) bacteria In the n.asopharynx m.y pass up the pharyngotympanlc tube and g;~in aca" to the middle"'· From the.re they m41Y p;qs to the mastoid air cells and flnally enter the tr.nlal UYlty, causing meningitis.
HeGtl - - I. OVnJGI Bones
x---=---==--=-----;;~~~~~-£mmal
llalUS11c: opening
..=;~--MISIJlld
frmmen
•
Styloid
=-- --4-- - - Altlculn tlbefde
PI'Xle.SS
- -11=!--- -
lll~ndlbul;lt
fossa .,..., __
£mm.1l liCDUStlc opening
- - --rl--- for.men lllastcld
D Lcfttt=mponlbone liltl!r.lllllew. The prlnclp;tl structiJres of the temporal bone ire Ia· beled In !he diagram. An emrss.uyveln (seep. 9) p;tsses lhrough the mastoid foramen (extl!rnal cnifia! shown ir1 a, intl!rnal orifia! in c), 01nd the chordiltymp;tnl passes lhrough the medlill part of!he petro· tympanic fissure (see p.147). The nnistold process develops graduilly In life due to trutlon from the sternodeklornastold muscle and Is pneumatized f'rDm the inside (see C). b lnh!rtor'lltew. The shitllow irtlaJiar fos.sa of the temporomindlbular joint (the mindlbularfossa) Is deirlyseen from !he Inferior view. The fac:lal nerve emerges from the b.ase of the slculllh~h !he stylo·
;a
mastoid for01men. The Initial part of the Internal jugulilr vein Is .. ~ herent to the jugular fossa, and the lntemil carotid 01rtery passes lhrough the Cilrotld Cinal to enttr the skull. c Medlallllew. This Yii!Wclisplays the internal orifice of the ma.stDid f~ ramen and the Internal at1lustlc meatus. The f.lclal nave and vestlbulooochleilr nerve are among the struc!IJres that p;tss through the Internal meatus to enter the petrous bone. The part of !he petn:MlS bone shown here is also called the petrous pyromid, whose apex (of· ten cillled the "petrous apex.") lies on the Interior of the b.ase of the skull.
23
Head - - 1. CmtifJI Bones
1.12
Sphenoid Bone
hlatfnebone
fl1l0till bone
Sphenoid Sptlenold bone
VOmer
Ocdpllll bone
T81110nll bone
bon~
Ocdpltal bone
Tmpcnl bone
P.Jrtetalbone
A PosiUon ofthuphl!tlold bonelntflullull
The sphenoid bone is the most struttur.~llycomplex bone in the hum~n body. It must be vlewed from wrlous aspects In order to appredate all Its fe.rtures (see also B): ;a I.JI:e of the skull,
external ;aspect. The sphenoid bone combines
With the occipital bone to fonn the load-beartng midline strutture of
the skull base. b . _ of the skul, ln'lllmal iiiPKt. The sphenoid bone fomu the
boundary between the anterior and middle cranial fossae. The openIngs for the passage of nerves and vessels are dearly displayed (see details in B). c; ~1111-. Portions of the great\!r wing of the sphenoid bone can be seen above the zygomatic arch. and portions oftile ptef)'gold process can be seen below the zygomatic .arch. lllo!l!the bones that border on tile sphenoid bone In eKh VIew.
B llollrtitd sphenoid bDne
lnlintor ~~~-(Its position In situ Is shown In A). This VIew demon· strates the medial and latl!l"al plates of the pterygoid process. Be· tween them Is tile ptsygold fossa, which Is oc;cupled by the medial pterygoid muKie. The for.lmen spinosum ;nd foramen not\Jndum provide pa'dlways through the base of the skull (see als;o Inc;). b Antl!t1'or llfew. This VIew Illustrates why tile sphenoid bone w.~s orfg· ln.ally called the sphecold bone (•wasp bone") before a transafp· tion em:w turned it into the sphenoid ("wedge-shaped") bone. The apertures of the sphenoid sinus on each side resemble the eyes of the wasp. and the ptsygold processes oftile sphenoid bone fonn Its dangling legs. between 'Which are the pterygoid fossae. Thfs111ew .also displays lfle superior ortlital fissul'l!, 'Which amnects the middle era· nlal fossa with the orfllt on each 31de. The two sphenoid sinuses are separated by an ln!l!malseptum(see p.21).
;a
24
Sphenoid -..,.::..-~~=' bone,
g!Nter -..fng
Temporal c
bone
c Supedar W!w. The superior view displays the sella turcica, whose central depression, the hypophyseal fossa. contains the pituitary gland. The foramen splnosum. for.~men ovale. and foramen rotundum can be Identified posteriorly. d Plllterklrllfew. The superior orbital fissure is seen particularlyclealfy In thlJ Ylew, while the optic canalis almost completely obKured by the an!l!rtorclfnold process. The foramen rotundum Is open from the middle aanfal fossa to the external b-ase of tile skull (the foramen spinasum is not visible in lflis view; compare with a). Because the sphenoid and ocdpttal bones fuse togelfler during puberty ("tribasllar bone•). a suture Is no longer present between the two bones. The cancellous trabeculae are exposed and have a porous .appearance.
Head-- 1. CmtifJIBones
1.13
Occipital Bone and Ethmoid Bones
~totlanofthe GCqlltal bone llntotfluxtl!lnal bale of the dalll lnferlorvlew. NoU>the relationship ofthe ocdpltal bone w the adjacent bones. The ocdplt.ill bone fuses ~th the sphenoid bone during pubertytoform tne •bib
A
Jugularpn:aD
Foramen
magnum ~n~ar--~~-----
c:anal
-----=.;...~~~--~------~--~
lnfu!or
nuchal line
oalp!l
foramen ------':it-"i:--~~-m~V~um
•
Superior
Supnme
nuo:hallkle
nuthllllne
B llolltltd outpltal bone <11
lnlilrior W.W. This view shOW51fle basilar p;rrt of 1he ocdpttal bone. whose anterior portion Is fused to the sphenoid bone. Thecondylarca· nal temllnates posterior to the occTpltll condyles, while the hypoglos· s.al canal passes superior to the aa:ipil:lll ctJndy!es. The ctJndy!arcanal lsavenousdrannelthatbeglnslntheslgmoldslnus;rndendslntheocdplt.ill vein (emlswry vern. seep. 9). The hypogloswl canal cont;rlns a venous plexus In
26
b tat l~ttnl W!w. The extent of tne oa:ipit.ill squama, which lie$
HeGtl - - I. OVnJGI Bones
C lntlefriltlon of the ethmoid bone Into the lntem~l biiSe of the
D lnleil'illtkln of the ethmoid bor~e Into the f.ld~lskeletlln Anterior 1/few. The elhrnold bone Is tile central bone of !he nose and
skull
Superior view. The upper partion of the etnmoid b~ne forms p~rtaftne ~nrerior aanl~l foss~. wfllle Its lower pmlons contribute structur;llly to tne naiNII cavities. The ethmoid bone Is bordered by tne front;rl ;md sphenoid bones.
paran;~wl~nusu.
1-+r-"T'':--:-'---
Su~r
meatus
C~ga!ll---
Anterfor ethmoid foramen
..l
- •
elllmold ~ for.rnen
llostetfor
'
•
Olbltll plate
Middle
c
d
concha
Leftloltar~~hltew. Vle>Mngthe bone from tile left slde, we observe the
E lllolmdethmoldbone
c
;a SUpertor lllew. This view demonstr.ttes tne afrta gall!, which gives
perpendkular plate and the opened anterior ethmoid cells. The orbit Is separated from the ethmoid cells by a tilln sheet of bone called the orbital plate. d Posteliorlll-. Th!s Is the only view ~flit displays the undn;~te process. which Is almost completely covered by tile middle concha when In situ. It partially occludes the entrance to tile maxillary sinus, the semilunar hiatus, and it is an important landmark during endOSa:Jpic surgery of the m;~1dllary sinus. The narrow depression between the middle coocha and undnm process Is ailed tile ethmoid Infundibulum. The frontal sinus, maxillary sinus, .and ;mterfor ethmoid cells open into ttl is "funMI." The superior concha is located at the~ nor end ofthe etflrnold bone.
al:t.ichment to the falx cerebrt (see p. 188) .md the hoiUolrtally dl· rected cribriform pl;!te. It is perfor;ated by fur;amina ttl rough which theolf.lctoryflbers pass from the nawl c:.Mty Into tfle anterior aanlal fossa. With Its numerous foramina, !he cribriform plate Is a mechanl· ally weak structure that fractures easily rn response mlriluma. Th~ type of fracture is m;~nifestl!d clinically by cerebrospinal fluid leabge from the nose ("runny nose" In a pMientwltfl head Injury). b Antl!ffor VIew. The anrerior view displays the midline structure !:hit separ.ltles the two nasal cavities: the perpendicular platl! (which resembles tne pendulum of a grandf.ather clock). Nob! also the middle concha. which !s partoftheethmold bone (oftfle conchae. only the lnferfor concha Is a separate bone), and tne ethmoid cells, which are dusttred on bolh sides afthe middle conchae.
Hftld - - 1. c:nmlallona
1.14
Hard Palate
MIXIIIo MDIlory stn~a
Pilatlne
bone Sphonaid bone
• A lntegr.Uon of the hlrd p1!m lntllthe lillie afthulcull. Infertor view.
MDIILio Ch~e
Sphtneld bono
Palltlne bone
Vllm•
I . . _ afth• lard plliltll • SupertDrwlew. The hard ~lm Is a hortmn-
ul bony plate formed by ~Its of the miXrna and ~LioUne bone.ltsetWs as a ~rtltlon bebm!n the orill ilnd nasal cNtles. In thls vttwwure loolc:lng down at the ftoor ofthe nasal Cilvtty, whose lnft!rlor surface fonru the roof of the o~l c.wlty. The upPfl' porUon of the rNxllla has been ranO'ied. The palilltlne bone Is bordered postlflor1y by the sphenoid bone. b Jnfe.tor view. The choanae, the posterior openlng5 of the niiHI cavity, begin at the postet1or border ofthe hard palate. c Obllqua poltllrlor This view demonstrat:es the dose relaUonshlp between the o~land nasal cavities. Nom how the pyramidal process ofthe ~Iatine bone Is Integ rated Into the later
vi-.
Middle a>ndla ChC11111e
Sphorloid bone
'
28
1/cmer
Head - - J. CranlaiBones
lndslw -
-....,..:!.11---
anal
c
Hlrdp~l.-
1
Superior~~~- of the floor of the Nsal c-
ity (• upper portion of hard palate) with the upper put ofthe maxilla rei!IIJiofed. The hard
-l!.y -----::;5::; sl-
"hnswrse
palate~r--stheoralavttyfmrnthena
Poi.Unr~.
-~----::!~~-~,.,_::c....__
perpondla.olor ~
poliltlne>ubn
G - r ----;;:-...~ pallllnec.ool
I
lndslvo ----~~~-...:,V an•l
r ...n....,.
defectln~ngthellp.alveolus,andpalm).
- - . . -.........--l'ilotil~prote$$ of111111dlo
Nom: the Nsal cavtty (whose floor Is formed
by the hilrd palate) communicates with the nuophal)'llll by VRY of the choilnae.
',-----,-:------'~~~~-Medon
pohrtlnuulun!
paiiiiMIU!il"'
4:
G-r pol.une furomon
lnfa1or ---~ orbit!Iftlsu"'
Ar*rtor dilold PfOaSil
O•tllmaf sphenoid sinus
wl cavities. The small a nal that linb the or.J and Nnl CMIIIies, the Incisive anill (present here on bolh sides), merges within the bonewform one canal. whim opens on the lnfertor sulface by a single ollllce. the indsi~ foramen (see b). b lnfef1Dr VI-. The l't¥0 horizontal processes of the mullla, the palnfne processes, grow t.Jgdher during development and become fused at the median palatine suture. Failure oflflis fusion results in a c/
-;t:=:::-----.,.!;fi-.411'~11fl'i
ObllqiMI ,_.lior vi- of the posterior part of the sphenoid bone at the level of the sphenoid body, displaying bolh sphenoid sinuses separated by il septum. The dose tGpographlul relationship between the nasal cavity ~nd hard palm can be itpprec:lated In this vtew. If the hard palm Is unfused in a nursing infant due to a cleft anom~~ly (see It), some of the Ingested milk w111 be dr-ted from the oral cavity and will entwthe nose. This defect should be dosed with a plate lmmedlatdy a~r birth tG permit SiltlsfactGJY oral nlll1ttfon.
a Alltl!rlor ww. The mandible Is connected to !he lllscerocr
the mandlbularoondyle. This "hN
30
b Posterior ww. The mandibular foramen Is particularly wdl dis· played In this1/few.lttransmrtsthe Inferior alveolar nerve, wltlch supplieuensory innervation to the mandibulartnth.IU temninal branch anergesfromthe mentalforamen. The twa mandlbularforamlna are Interconnected by the mandibular c:.1nal. c Oblique left lltel'll ww. This 11tew displays the coronoid process, the condylar process, .ilnd the mandibular notch between them. The coronoid process Is a site for muscular attachmmu. while the oondylarprocessbe.ilrslhehudofthemandlble,wltlchartlculateswlththe mandibular fossa of the tempor.ill bone. A depre.sslon on the medial side of the carldylar process, the pterygoid f\wea, givu attachment to portions of the lmral pterygoid muscle.
Head - - J. Cranial Bones
•
c
8 Age-nilmld dlanga., themindlble The strudure af the mandible Is greatly lnflul!llced by the alveolar processeJ of the teeth. Because the angle of the mandible adapts to changes In the ;alveoli r process, the angle betvMen the body and ramus also varies with aQe-mated chingu in the dentition. The angle measures ipproxlmately 150' it birth, ;and approxlmatdy 120-130" In adults. cleaNsing to 140" In the edentulous mandible of old age. • M birth the mandible is without teeth and the alveolar pgrt has not
yet formed. II In dlllchn the mandible burs the deciduous teeth. The alveolilr part is nill maMiy poorly d~ed beause the deciduous teeth lire considerablysmllller thin the perminent teeth.
Lesoorhom
•
Gnntrham
c In adults the mindlble be<~rs the permanent teeth, and the lllveolar
part of the bone Is fully d-loped. II Old ill" b c:hilrarnrized by an edentulous mandible with resorption of the ;alveoli r process.
Nom: the resorption afthe alveol;ar process with advanced ;age leids tD a dJ~geinthe~itionofthementalforamen(whidJisnorm;~llylocated
bel- the secGnd premolllr tooth, as In c). This !Nnge mmt be tlllcen ini:D account in surgery or dissections iiMIIving the mental netw.
l..ftJerham
G.-hom
Body
Cireollor ham
c C Hyglclbone
a Anterior vtew, II posterior view, c oblique left l~ter.~l view. The hyoid bone Is suspended by muscles between the oral floor and Ill 'l"'X In the neck. although It Is Usted among the cranllll bones In the Tmnlnolog.lo
Anolomla!. The greater hom and b..!y afthe hyoid bone are palpable In the neck. The physiological movement of the hyoid bone dur1ng SWill· lowing Is also palpable.
31
Head-- 1. CmtifJIBones
1.16
Temporomandibular joint
Zygomrtfcp- - -
oftl!mponlbone Petrotymp;~nlc
---:.:....._ __
fluure
A Mindlbul;n foa.1 of the tamporvm;mdlbulu!oint lnferlorvlew. The head of!he marldlble artkula!l!s wlt:h the marldlbular fossa In the temporomandibular Joint. Tbe mandlbularfossa Is .a depres-
sion in the $CJu;rmous p;~rt of the temporal bone. The articular tuberde Is loc.m!d on the anterior side of the marldlbular fo$$a. The head of the marldlble (see B) Is marki!dly smaller than the mandibular fossa, allow-
lng It to NYe an ;ulequ;r!l! range of movemmt (seep. 35). Unlike olfler irtlallar surfaces. Ule mindlbular fossa Is C
Hmdof mandible
Neck of
mandble
Ulgula \r-f- - 1111ndlbular foramen
• B Head ofthe m.~ndlble In the rfght tl!mporvmlndlbul•r Joint a Anterior view. b posterior view. The head ofthe marldibleisnotonly marbdlysmaller than the artlcularfossa but aiJO has a cylindrical shape. This shape further lnaea1es the mobility of the mandibular he
32
c
llglments of the lefttl!mpororn~~..joTnt Lateral view. The temporomandibular joint is surrounded by a relatiw.ly lal!.e<~psule, which pemntts physiological dislocation durfngjawopenlng. The joint Is stiblllzecl by three ligaments (see c ;md D). This la!l!r.~l view demonstr.rtes the strongest of these ligaments, Ule la!l!r.1l ligament. which stretches t:M!I' the capsule and is blended with it. The weab!r stylomandibular ligament Is also shown.
HeGtl - - I. OVnJGI Bones
i'tA!tygospnous
Artla.l~r
l1111rnent
dsk
Millldbular
Jolrt
nolth
Glp$Uie
Sphenornand~
Headd
mar.dlbl~
bular ligament
D Right tlmpoi'Omilrldlbulilrjo~ilnd lgiiiFMII'Is Medial view. The sphenomandibular ligament c:<~l'l ilso be ldenUfled In thlsvlew.
E Openld 11fttllmporomilndlbulilr Joint Lateral view. The c:<~psule extends postertorly to !he petrotympanic fissure (not shown here). Interposed betweel'l the mandibular he
F Dlsloalt.lon oftfle tempcii'Omlndlbullr Joint The he
G Sensory rnnerviUCin of the tl!mporomandl'bularjol'nt capsule (afterSchmiclt) Superior view. The temporomandibular joint apsule IJ supplied by articular branches arlsll'lg from Utree branches ofthe mandibular dlvlslol'l af!he trfgemlr~al nerve (o.t V
A Moftmenb of the 1111ndlble In thetanporom~ndlbullr )olflt Superior view. Mostofthemovemerns In the temporomandibularjoint are complex motions that have three main components: • Rotitfon (openlfl!l and dosing the mouth) • ll'anslatiOn (pl\ltruslon and retiUSion of!he mandible) • Grinding movemenU during mastitlation
a
t~Gtatian. The axis for joint l\ltation runs tran~e!y through beth heads of!he mandible. The two~ Intersect at an angle of approxl· mate!y 150' (range of 110-1800 betwHn lndMduals). Durlr~g this m011e1111ent the temporomandibular joint acts as a hinge joint (ab· ductionfdepression and addLJCtianJelevation of the mandible). In hu· m;ms, pure rotOitlon In the temporomandibular joint usually ocaJrs only during sleep wtth the mouth slightly open (apenure angle up to .ilpproxlmately 15', see Bb). When the mouth Is opened past 15', rotation is rombined with translation (gliding) of the mandibular head.
34
b Thlnslltton.ln this mcMrnentthe mandible ls adwnced (pi'Gtl'Uded) ;md retracted (retruded). The axa for this movement are parallel to the median axes through the C4!11ter of the mandibular heads. c Crtndlng mowments In the left tl!mparam1ndlbular Joint. In describing these laterai~T~~Mments, a distinction Is made between the 'resting condyle" arid the 'swinging condyle." The restlfl!l condyle on tile left working side rotates .ilbout;m .almost vertical .axis through the head of tf1e mandible (also a rotational axis). while the swingIng coneyle on the right bolla riCe side swlr~gs forward and lnWilfd In a troarulatlonal ITI
HeGtl - - I. OVnJGI Bones
Mf(ulardllk Ht.lid of mancllble '/fiJ_.._ _ joint (4)51.fe
..........._ .,. ftC'
lara! ptelygcld musde,
Wi!rforp.n
8 Movemllllltl ofthe tl!mporom~ndlbuln Joint 1St later.illllfew. E.ilch dr.ii!M'ng shows the left temporomandibularjoint iocluding the articular dislc .ilnd apsule and the later.al pterygoid mus· de, and e9Ch schematic dlilgram ~t right shows the correJpondlng
b Mouth opened to 15'. Up to 15• of.ilbductlon, the head of the ttlilndlble remains In the mandlbularfosS.il. c Mautfl opened p111t 15'. At this point the hl!>ld af the mandible glides forw.lrd onto the articular tubercle. The joint illds that runs transwnely through the mandibular head Is shifted fotwilrd. The artlculardlsklspulledforwardbythe supertorpartofthe lateral pterygoid musde,. and the head of the mandible is drawn forward by the lnfmorpartofthatmusde.
35
Head-- 1. CmtifJIBones
1.18
The Teeth in situ
Nl!dc
}~
}A Principii partsofthetDDtfl • CnMn
• Nedc • Root
I Penn;ment teeth of;m ildult a Malia. Inferior lllew displaying the ocdu· s.1l sul'fac:g of thetl!eth. b M;mdlbll. Superior lllew. ~ch
tooth is given an identifiCJtion code (see p. 38) tD describe the spedflc loc.rtfon of dental lesions such .u arfes. ~ch half of the maxilla and mandible a~ntains
the following set of anterior ;md posterior
(poslcinlne) teeth: • Anterior teeth: two lndsors ;md one canine tooth. • Po:ltl!rlor ll!eth: two premolars and three
mola!'l.
lnclsart
b
36
Head - - I. OVnJGI Bones
c
b
C Ocd.tsal pl1nund dental an:her. "· b '!WH oft.th ~nd the ocdUMI pllne. The miUdlla and mandible present a symmetrk31 arr.;mgernent. With the moutil dosed (ocdw.ill position), the maxillary teeth are .ilpposed to their mandibular counb!tpatts. They are offiet relative to one another so that the cusps of one tooth flt Into the flssureJ of the two opposing teeth (cusp-and· fissure dentition). Ikeause of this arr.-mgement. every tooth comes Into contact With two opposing teeth. Tills offset results from the slightly gne.ilb!r width of the milleillary incisors (seep. 39). The ocdu· Jal plane often fomnJ a Juperiorlyopen arch (von Spee curw). c Dentllerches. The teeth of the INX!IIa (green) .ilnd marwllble (blue) are arr.anged In superior and Inferior.ilrche.s. The superior dent.al arch fonns a semi-ellipse while the inh!rioc- arch is $~\;aped li~ a p;~rabola.
---Enamel
~
SllarpeyAbers
---
Allltdarw.~ll
~ f}{t - -, '
'
Cementum
E Supportklg 1tn1cturu of the tDotfl: the periodontium The tooth Is .ilfldlored rn the .illlleolus by a special type of syndesmosis ailed a gomphosis. The tissues th.ilt imrest arid support the moth, the periodontium, com!Jt of: • • • •
The periodontal ligament The cementum Thea!Yeolarwall The gingiva.
The Sharpeyflbers .are collagenous fibers that p;~ss obliquely downward from the allll!olar bone and insert into the amentum of the tooth. Thil> downward obliquity of the fibers transforms mastk:atlxy pressures on the dental arch Into tensile stresses acting on the flbefs and anchored bone (pressure would lead to bony <~trophy).
D HhltoiDgy af I tDotfl
F Cl:lnnec'.tM tissue flbln In tile gingiva
lllustr<~ted
Many of the tough collagenous flber bundln In the connect!-tlssue core of the gingiva above the alveolar bone are arranged In a screw-Uice pilttem around the tooth, further strtngthenlng Its attachment.
here for a mandibular !ndsor. This diagram shows the hard tissues of the tooth (enamel. dentine. cementum) as well as the soft tis· sues (dental pcJip}.
37
Hftld - - 1. c:nmlallona
1.19
Permanent Teeth and the Dental Panoramic Tomogram
A Coding dJejM!II'IIIInenttHth In the United States, the permanent t:Hth are numbered sequentially mher than bdng aulgned to qUidrants. Progressing In a dockwlse fashion (from the perspecive of the viewer), the b!l!th of the upper arc
are numbered 1 to 16, while thwe of the lowtr are considered 17 to 32. Note: The tnird upper molar (wisdGm tooth) on the patient's right
Is considered 1.
----Meslllll
Bue<.ai--
-
B Detlg..UOn af tDath IU!'fllc:es Superior view of the ma ndlbular dental arch. These designations ilre used In describing tne precise location of smilll carious lesions. The tenn krbla/ls used for Inelson and canine teeth,and buccoJ Is used fur premolar and molar teeth. The t.tm lln9ual Is used far the mandibular teeth and pa/atolfor the m~llary teeth.
38
- - Ungual (Pilatal)
Head - - I. OVnJGIBones
32
--4-~""-
lhnlmclar (wisdom tooth)
28
c
27
26
25
Dl!ntll panoramktDmogn~m
The dental panoramic tomogr.~m (DPT) Is <1 survey radlogr<~ph that al· lows a prelrmlnary <~~e~ment of the t:emporoiTiilndlbular joints. miiX· lllary sinuses, maxllloiTiilndlbular bone, and dental status (c.1rtous le· sioru, location of the wisdom tzeth). It is based or'l the principle of con· vent!oBaltomographylnwhlchtheX·raytube;mdfllmaremovedabout the plane of Interest to blur out the shadows of structures olltS!de the sectional plane. The plane of Interest In the OPT Is shaped like a parab· ola, conforming tD the shape of the jaws. In the case shown here, all four wisdom teeth (third molars) shocJid be mracted: teeth 1, 16, and
17 are not fully erupted and toad\32 is horizontally impacbl!d (cannot erupt). If the OPT r<~lses su~plclon of c<1ries or !WI: disease. It should be followed with spot radiographs so that spedflc regions of Interest can be ev.aluated at higher resolution. {Tomogram courtesy of Prcf. Dr. u. J. Rtlther, directar of the Depart· ment of Diagnostic Radiology, Center for Dentistry and Oromaxlllof.ldal Surgery. Eppenclo!f Un!Yerslty Medical Center. Hamburg. Gennany.) NDIJe; The upper Incisors .are broilderthan tile lower Incisors, le.adrng to a •Cllsp-and-fissure• type of ocdusion (seep. 37).
39
Head-- 1. CmtifJIBones
1.20
Individual Teeth
Oaloml J\lrf.u:e (1--ofthe CITM'II)
.....--...... ublal
Distal
•
•
Distil
Palmi
LiliaI
b
c
I
Labial
UnsJUII
A lnc:hol'$
Centnllrldsor (9); b la!I!AIIrldsor (10): c lower Incisors (23-26; 24
;a
B C.nklcs {Culplds} Upper canloo (11 ): b lower e<~nlr~e (22): • - the tip of the crown. which represents the ocdus.1l surface. The aown Is thlckerme.slallythan distally, and has greater curvature (arrow). lrl dogs, these teeth (also known a$ cuspids or t'Yt' ~th) a~ developed into fangs fDr gripping the prey between the jaw'lo-hence the tam "canine.•
;a
Ocd1.11al
surface
(f) •
Buccal
Dlst.ll
b
Buccal
DISUI
g oa:kls.ll
\1 c
Bucxlll
Distil
C Pranol;us(llcutphfJ) First premolar (1st blalspld. 12); b second premolar (2nd bicuspid, 13); c flrrt premolar(21); d second premolar(20). The premolars l'l!p· resenh transitional fDrm between the incisorsand molars. Like the mo· Iars. they have cusps and fissures Indicating that their primary function Is Ule grfndlng of food. rather than btung and tearfng. The upper left
;a
40
d
Bucxlll
~umo;
Distal
flrst premolar (12, a) Is the only premolar that has two rooa. 113 mesial surface which borders the neighboring proximal tooth often bears <1 small pit that rs difficult to dean and vulr~erable to cartes. The othtfpremolars have one root that is divided by a longitudinal groove and eo& talns two root canals.
Head - - J. Cranial Bones
•
J
luwl
...
OtdUSil ~
..t
J Distil
Pa~l
II
Bu«iiil
.~J Dimll
Ocd....,l
su..U
:J 1'11&.11
Otdusol surface
Ocdusal sumao
c
llucal
luaal
Unguol
D Malilrs
• First malar (6-yr malar, 14); b second molar (12-yr molar, 1S); ' third molar (wlldom tooth. 16): d flrst moln (19); e second molar (18); I third molar (17). Most of the mol1rs hllll! three roots to v.tthstand the greater mastiatory pressures in the molar region. The rOGts ofthethlrd molars {the wlsdomtKth, whld1 erupt.tb!r 16 ~rs ofage,
llu
DINI
Ungual
U~~guol
If it ill) a~ mm monly fused t:ogl!ltl•. pirtlaJ Iarty In the upper ltlln:l molus. Bec<~use the molars aush and grind food, they have a crown wlltl a plilteiu. The !Inures b~ the OISps are a fn!quent site of canes formitlon In idolescants. No~: The term llnguo/ls used for the rna ndlbullr meth. the term polrrtu/ for the mnlllilryteeth.
41
lkfHI - - 1. Cnmlallona
1.21
Deciduous Teeth
loo o
c=,.c:.- -
&months
l)Ur
•
•
c
A Deciduous IMth Dl the left side The deciduous dentition (baby teeth) consists of only 20 teeth. Each of tne four quadrants contains the following teeth:
• Centrillndsor (first Incisor) b !Ae111l incisor(srcond incl- )
c unlne (aJSpld) d First molu (6-yr molar) 1 Se<:ond molar (12~ molar) To dlstfngursh the deC:Iduous tJtetfl from the permanent IMI:h, they are coded with letten. The upper ardlls l11beled A1x1 j, the lowef' Is labeled KtDT(seeD).
I E'ruptlon ofthe tMth The erupljonsofthedeclduouund pamanentteeth are called the first and second dentitions, respec:tlwly. The lndMd u1l teeth are listed from left to r1ght (llf_..s perspectlw) and the types of t2etfl1re ordered
c Eruption pdllm Dldw adduoul •nd p.11111nlnttwth (afll!r Meyer)
The eruption pill:tern Is nlus1nlted for the upper left teeth (deciduous tJteth In blade. penna nent tl!eth In red). Knowing the Urnes of eruption of the teeth lsdlnlcallylmportant. illS these diu c1n provide a bulsfor diagnosing growth debys 1n children.
Head - - J. Cranlal&mes
D Coding the dldcluo• tad! The upper right molar Is considered A.. The lettering then proaeds dockwlse <~long the upper arc ind back IITOIIIS the lower. E Denlftlon af 1 5-yuMIIId chftd Anterior view; c, d left lateral view. The
1, b
interior bony plate over the roots of the deciduous teeth h.u been remowd 1D display lfle underlying p~rmiln~nttuGth boos (pelt blue). This age was selected beause iII of lfle deciduous teeth h.ilve erupted by lflls time ind ire ill stlll present. Theflrstpermanentt»oth. the •fi-yea r molar: also begins to erupt at this age (see C).
1'tn111nont •
l'l!rrninent CI!!Vol ndoor
loUnl ndsor
Dec:lducus llll2rlllndoor
DedduoU> anln~
Anterior vtew of mullla (e) and rNndlble (b); left latl!r~l view of maxill~ (c) and m~ndible (d).
Ptn11onont
Pwmonont
PelmoMrt
antrollnd>or
lmnllndsor
anlne
Second permanent
Second dKiducus
main
molor
4:~,_--~-- Second
permanent premolar
c
DedduaU>
DedduaU>
lottr;l hdsar
canhe
Arst dedducw molor
Frst dec:tduoLB mdar
Dedduous - latl!llllilclsar
43
2.1
Muscles of Facial Expression, Overview
Gals----=--=- - -
aponeurotica {tpiallnlal aponeuros'tl)
Lev.ltlr lab! I
superforts alaequtnasl
~-=--~r.,•-:t,.,I--Et--- ~rlabll
S1,1perfOriS lllit!quenl!l
Z)'JI(Im;Jt~M
Lev.ltlrlabll---~~~~~------~~
minor
superfor!s
DetnSSQr arciAIOI!s
- - - -.1!11
Depressor llbOimrfor!s
A MllldH ofliufalexpresslon Anteriorview. The superfici~lli!Yl!r of muKies 'i$ shown on the right half of the face. tile dHP layer on the left half. The muscles of facial eJq~res· slon represent tile superilclal muscle layer In tile face and vary greatly In their dewlopment among different lndl\ltduals. They arise either dl· reedy from tne l)eliNteum or from adjacent mU~~Ciu to which tney are connected, and they lrueft either ontD other facial muscles or directly lniD the connective tissue of the skin. The classic scheme of classifying the other somatic musdes bythelrorfglns and lnsel'tfons Is not so easily adapted bl the faci~l musdH. Bec~use the mU~~Cies of faci~l exprnsion terminate directly In tfle subcutaMOUS fat and because tfle superildal bodyfasda Is absent In the face, the surgeon must be particularly careful
44
when dissecting In this region. Becawe ofthefrcuuneousattachments, the facial muKies are able to move the facial skin (e.g., they can wrinkle the skin. an action tempor.ufly abolished by botunnum to!cln Injection) and produce a vartety of facial expressions. They also serve a pnotecttve functiOn (especially fi:lr the eyes) and are actllle during food Ingestion (closing tne mouth for sw.~llowing). All of the facial muscles are innervated by branches of tfle facial nmoe, while the muscles of mastlc3tlon (seep. 48) are supplied by motor flbefs from the ttlgemlnal nerve (the masseter muscle has been leftln place bl representthese muKles}. A ttl oro ugh understanding of muscular anatomy in ttlis region is facilitated by dMdlng the musdes Into different groups (see p.47).
B Muscles offld'll expression Left lateral vi-. The superiicial muscles of the ear and neck are particu· larly well dbplayed from this pmpectlve. Atough tmdlnous sheet. the galea 01poneurotlca, rtretches
rlcularts superior muscle, artses from the lateral p;1rt of the galea apo· neurotica.
45
Hftnl- 2. Mu.:luoftMHnd
Muscles of Facial Expression, Actions
2.2
l..ftltDrllbil ..porlods ••equtnMI
!L.--'---
1
l..emilr llbllsl4*ioris oiHquenul
NIISIII5
Orbltulorb oarll,
il
Antlrtor
b
loatnalaat
orbital part
A Muscles of~l expreMJon: p•lprebnrl fissure •nd rue
Anle!1orvlew. The most functionally lmpoortantmusde lstheorfllai/Grlsocufl, whkh doses the palpebr~lftssure (protective reflex against furelgn matter). If the action of the orbicularis OOJIIIs lost because of facial nerw paralysis (see also D), the lou ofthls protective reflex will be accompanied by drying of the eye from prolonged exposure to the air. The function of the orbicularis ocullls tated by i1Sklng the patient to squ- the eyelids tightly shut.
b The orbicularis oculi has been dissected from the left orbit to the medial Cilnthus of the eye and reflectl!d anle!1orly to demonstrate Its lacrimal part (called the Horner muscle). This part of the orblwlarls oculi arises mainly from the posterior IKrimal crest. and Its ;action Is a subject of debate (expand or empty the laa1mal sac).
ZygamollaJS
~omlllo.ls
mlnar
minor
l..ftltDrlabll suponorls ~
I.J!oRb>r _
__,_
_ __1 ....-
anp.~llorls
.,.ulloris
llua1nllllr
IUiorlus
• B Mlllda oft.dll upnsslon: mouth • Anter1or view, b left lat•~l view, c left lmral view of the deeper laterallayer. The orllkularls orfs fonms thl! muSOJiar foundll:lon of thl! lips, and Its contraction closes the oral a perrure. Its fu netion can be tested by askIng the patient to whistle. hdal nerve par;llysls mil)' lelld tu drinking difficulties because thl! liquid 'Mil trldde back out of thl! undosed mouth during ~!lowing. The~ lits ilt a deeper lev.!l and forms the foundation of111e dteek. Dvrlng miiStlcatlon, this muscle movesfood In ~n the dental ardles from the oral Vtstlbule.
46
Orbltultrts OCIIII. l..nn.l part
.. L.evmr labll l~Orls
IJMtor angularls Bualnllllr
l.YlJamlllo.ls minor
Head -
D Muscles afhdal expression: fundf01YI111raups The various mimetic muscles are easier to learn when they are studied by regions. It Is useful dlnlc:ally to dlstlngubh between the musdes of theforeheid and JNipebralftssure andtherestofthe mimetic muscles• The muxles of the fo~ead 1nd p;~l pebral fossure are inntnrllted by the superior branch of the fulal nerve. while all the other mimetic muscles are supplied by other fadal nerw branches. As a result, patients with artral fadil nerw paralysb a~n still dose their eyes whde patients with perlphe1111l t.ldil nerve p.aralysls unnot (see p. 79 tor further deUlls).
•
• .._,) c
2. Musduo(tM Head
d
calvaria
fpicranill mulde. mnslltlngaf:
MuKit rJI the alvaria
- Ocdpltofronblls (fronta I and ocdpltal
Wrinkles the foreheiid
bellla) -
• P';llpebr;~l
g
h
--
fissure
TemporGptl~etills
()ri)lcularfs oculi, mnsisting of: - Orbital p;1rt - Palpebral pi rt - Llcrfmol port CorrugWir superdln Dopras«superdlO
Nose
Praa!na
Has no mimetic function
Tightly amtracts the skin ~tround the ~
P•lpebr11l rella. Acts on the lia1mil YC Wrinkles the ~b..-(11) ~the.,._
Wl1nkt.s the raot of the
nose ,._the naris (c) a.v.. the upper hp ond niSIIa(4)
l)lgomotlcUJ minor t
Risorius Ll!v_. llbn supertoril
LlYWII'11nguR o~s
C Olmges af hcllll aprealon 1
b c d • f
g h 1
J II
Contraction of the orbicullris oruli at the latend a~nthul of the eye expresses concem. Contraction of the con-ugator su perdlll DWJrs In response to bright su nllg ht "thoughtful brow.• Contraction of the naSIIIs constricts the naris and produces a cheery or lustful facial eJ!Prt!S$IOn. Forceful contraction of the lewtor labll superlorls alieque nasi on both sides Is a sign of disapproval. Contraction ofthe orbicularis oris eJCpresses detenn ination. Contrictlon ofthe bucclnll:or signals Sitlsfictlon. The zygomaticus majclf contracts during smiling. Contrictlon ofthe risorius reflects purposefu Iutlon. Contraction ofthe levitxlr anguli oris sigNIs se1f-11tlsfactlon. Contraction of the deprt!S$0r anguli oris sign;~ Is sadness. Contrictlon of the depnssor labll lnfmorfs depresses the lower lip
Dop11!1S0r ~tnguh oris Deprassor llblllnftrtorts
ClaMs the mouth (e) Musclt rJI the chftk (lmporUntclumg.ang and drtnldng) (I) IMge mulde af the JWC>mltlc arch (I) Small mulde of the
zygomlllc arch MuKit rAIIughter (h) El-lils the upper lip Pulls the CDmerof the mouth upward (I) Pulls the mmer of the mouth dCM'I1Mrd Q) Pulls the 1_. np downw~rd (II)
Mentalis
Pulls the skin of the chin Upwllrd ~)
Aurlcullril onlaior Auricularis superior Aur1cui;lr1J poste~or
Nedc
md expresses ptneverenoe.
Ant.rfor mulde of the •ur1de Suplrior muscle rJI the •urlde Posterior muKit of1M aurtde CUUneous muscle of the
neck
I Contraction ofthe maltalls eJq>reses Indecision.
•Ldtas refw to su!Hntr~ts In c.
47
2.3
Muscles of Mastication. Overview and Superficial Muscles
Oltemew of tile muscles d mestlmton
The m~uth is opened primarily by the suprahyoid m~ades and the fWc:e
The muscles of mastlc.rtlon In ttle strict sense consist of four muscles: ttle miSsell!f, temporalls, medial pterygoid, and lateral pterygoid. The primary function of all tbesemusdes is mclose ttle mouth and move ttle upperweth <~galnstthe lower teeth In <1 grinding action during milS· tlc.rtlon. The laterill pterygoid muscle ilsslsts In opening the mouth. The two pterygoid muscles are .-.!so ilctlve during mastlc.rtlon (for the rndl· vidual muscle actions, see A-c).
of gravity. The masseter and medial pterygoid form a muscular sling In which ttle mandible Is suspended (seep. 50).
Note: all muscles of mastlc.rtlon are Innervated by the mandibular nerve (ttllrd division of ttle trigeminal nerve), while ttle muscles of fac\;11 expression ilre lnnervilted by !he facial nerve.
• Supertldal part: zygomillllc arch (antlel'lor~thlrds) • Deep part: qgomatic arch (posterior third) ~rtton: • Masseteric tubenlslty an the mandibular angle • EMias the mandible • Protrudes the mandible ~nerwtlon: Masseteric nerw. a branch of the mandibular dMslon of the trigeminal nerw (CN V,)
Inferior temporal hne of the temporal fossa Apex and mecreal sumce of the COfOnoid process of the mandible • EMias the mandible, chiefly with Its wr1fal flben. • Retracts the protruded mandible With Its horizontal
~nerwtlon:
posterior fibers • Unilateral contracaan: masUcillllan (~MWs the mandibular head on the balance side bwanl) Deep temparalnerws, branches of the mandibular dMslan of the trigeminal nerve (CN VJ)
(i) Med..l ptefftCIIcl
Pterygoid fossa and latl!ral plallt of the pterwold process Medial surface of the mandibular angle (pterygoid tublniSity) Adlans: Bewtm the mandible ~nerwtlon: Medial pter,gold nerve, a branch ofttle mandibular diVIsion of the trigeminal nerve (CN v,)
Ortgtn:
~rtton:
I SchelllltltdthetemponiiiJmuscle
® ....... pterygoid OIIJln: • Superior part: lnhtemporal crest (gi'NII!r Wing of the sphenoid bone) • Inferior part: outersurfaaofthe lateral plate of the l*rygoldprocas
-.rtton: Actl-
~nerwaon:
C Schema\fc of tile medlill ;md lml'ill pb!ll'Siold muscles
48
• Superior part arUa~lar disk ofthe lltmporomandlbu· lar]Oint • Inferior part: condylar process of the mandible • Bilateral contraction: initiltes mouth opening by protruding the mandible and mGII!ng the ar11cul.ar disk forw.rrcl • Unilateral contracaan: eleolates the mandible to the opposlllt side during mastlatlan Lateral pterygoid nerw. a branch of the mandibular division of the trigeminal nerw (CN V,)
Pllrfeulbone
lhlntll bene
Te!1'C'O llli Is
Massetl!r.
l..1tl!r;ol ligament
superficial part
D Temponllland mu.seter U!ft lall!ral Yiew.11 Superficial layer, b deep layer. The masseter and zygomatic .arch have been partially remOIII!!d.Thefullextzmtoftheporulls Is shown In b. It Is the most powerful muscle of m.astlcatlon and does .approximately half the work of mastication. The a:msists of a superfldal part and <1 deep part. The t2mpor;llls ;md masseter act powerfully In r.arsrng the mandible and closing the mouth. Asmall por· tfon of the lateAI pterygoid Is vlsl· blelnb.
b
49
Hftld- 2.
2.4
Mu.:luoftMHead
Muscles of Mastication: Deep Muscles
Lllml
l*ll!IOicl. sLCJ('rlorpart
A l.Btel'lll and medl1l pb!rygold n!Kies Left l~ral viiMl'. a The coronoid process of the mandible has been removed here along with the l~r partofthetllmporalls sa that both pterwold muscles nn be Jftll (see p.49 Db). b Here the ttmporalls has been mmpletllly remowd, and the Inferior part of the l~ral p~d has been windowtd. The lotMJI pterygoid Initiates mouth opening, which Is then mntlnued by the supra-
see that ftbers from the lmral pt«ygold blend with the articular disk. The lateral pb!rygCiid fu nctlons iiS the guide mUKie of the temporomandibular joint. Beause Its vartous p;1rts (superior .;md Inferior) are acthle during all movements, its actions are more complex than those ofthe other mUKies of m;~stlatlon. The mrdlol pterygoid runs almost perpendicular tD the lmr.;ll pterygoid and contributes to the formation of a muscular sling that partially encompasses the mandible (see B).
hyoid muscles. With the tiiTiporomandlbulu Joint opened, 'WI! Ciln
He.ad tA mondblt,
artlo.lllr surfaoe
B MatlcatDry II'IUKU!ir 1llng Oblique posllertor view. This drawing tlurly shiMS h- the m;~sseter ind maJial pterygoid form 1 muscular sling In which the mandible Is suspended. By com bfnfng the actions of both muKies Into ll functianal unit, this sling enables ~ esful clQSure ofthe jam.
50
......,~~"-+---
Lllmlparrgold.
Wuforpart
HHd- 2. MusdesoftheHettd
Dur.ammr T~mponl
lobe
OpticEthmoid tdls ~d
!!nus
Temparab l.lrtml pterygoid, Ju~rlor put
Maueter, ~pp;ut
N~h~ryn~e
Lm!'al ~rotldgland
OnlP!wl')'nX
pterygoid,
lnftr'larpart Meehl pterygoid
Tongue ~ndblt
c
Muscles of mastSaUort, mranal sectron at the lewl ofthe tphenold tl'nus Postl!riorview. The topcgr~phyof the muscll!$ of m~stic.ation and neighboring structutl!s is ~rtirularfyWI!II displayed in this section.
A Mullde orfgfnnnd IMet'Uons on tfu~ tlnlll Leftli!ter.!lvlew. b viewofthelnnersurf.lce of tile right hemlmandlble, c Inferior view of the botSe of the skull. The origins and inM!rtions of the muscles are lrldlcated by color shading (orfgln: red, fnsu<11
Arteries of the Head, Overview and External Carotid Artery
AngUiilt --~---':\ ~l'tlery
,#~-""""-~~~~~--~ <~uricUar~
tnrenorlilblill --~.._-.,-~ ..ury facial~
~~d---~~~~
artery
A CMI'WWw of the 111a'tes of the held l.clt la!l!l"al view. The common CArotid irtl!fy diYicle:s Into Ute Internal CArotid .ilrtl!fy .ilnd external carctld .ilrtery at !he CArotid blfurCAUon, which is at tile approximate level of tile fourth cervial vertehr.a. The CArotid body (not shown) Is loCAted at the carotid bifurcation. It con· talns chemoreceptors tftat respond to <*Y!Jen deficiency In the blood
54
(hypQ-Qa) and to changes In pH (both are lmport.lnt In the regulat!or1 of breilhlr~g). While !he external CArotid a!Ury dMdes Into dghtbrinches (see D), Ute rntennal arotld artery does not br.ilnch further before entering tile skull (seep. 246, cen!br.al vessels). where it mainly supplies blood to the brain. It abo gives off brinches that supply 01reas of the facial slceleton (seep. 60).
8 Bnndt• vi the exlamll canrtlcl art.ry • Left lateral view, b anterior view. The four groups of branches vi the extenlil carotid irtl!ry are shown in diffi!rent colors (1ntl!rior brancha; red. rnedilll bnonch; blue, pomrior branches; green, term InaI branches; brown). Ceruln branches of tfte ext2m1l urotid 1rtl!ry (faclllartl!ry, red) cornmunkate Wltft brandies ofthe InternII uroad artl!ry (tzrmlnal br1nches of the ophth;olmic artery, purple) through anntomos~U in the facial region II. Extncerebral branches of the lntJennal arvtld artery are de-
•
safbed on p.60. lid:!mol
an>lld .a.,
lramal aratldartory
·. u::::::=r SU~ar
thyroid arlJI!ry
•
D Onnf-ofthe bnncha of the aum.. cai'IICid 1rtl!ry (more distill brandies are desatbed In the units below).
SUbsequent units deal wttft the arteries of the head iS they are grouped in the table below, faiiDWed by the branches of the internal cai'Dtid artery and the velru. Nlme.tthellra.._
c llranct. . afthe aum.r carotid artl!ry: typlallanamrnr and Vllrfanb (after Uppert and Pllbtt)
a In typk;il caHt (50 :1:) the f1clll 111Ery, llngUili rtery, and superior thyroid artEry i rise from the rxtanilll a road o~rtEry above tfte arotld blfui'CiiUon.
11-f v.rllllts: ll,c The suJ*ior thyroid a r1:lry arises at the level of tfte carotid bifuratfon (20 ~or from the common arotld artery(101). d-f T- or tit ree branches combine to form a com man 1runk: llnguobclal lru nk (18 X), thyroltngllil trunk (2 ~. or thyrollnguofidil trunk(l ~-
AniBtlll' bnnct.s: • Superior thyroid artary • Ungual • rtJory
• llryrur. thyroid uta nd • Onl floor, tonuue
• Facial artery
• 5upll'ftdal fKJal region
Medlelllrendl; • Ascending pharynge~l
• P'- to the skull base
artl!ry
Paltelfor••ndla: • Ocdpltalartary
• Oa:lput
• Posterior aur1culor artery
• Ear • MIISt'Qtory muscles, postBvmedlal
• 5uperftdilllmlporaI
part of tht faclll sktletDn, meninges • Tempor.tl ~n. !Mrt afthuar
artl!ry
55
Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k
External Carotid Artery: Anterior, Medial, and Posterior Branches
• A flcTIII artery, ~Ttalartl!ry, a'ld postertor aurlallar artery andtfltrrbl'lnches Left later~! view. An Important anterior branch of the external ~rotld artery Is the fac't.ll <~rtl!ry. wfllch gives off br~nches In !he neck and f~ce. The prlnclp.;~l ct!Mco/ branch rs the ascending p.;~lati'ne artery; the fl)nsi//crr bronch ~ ligated during tonsillectomy. Of the (rrcial branches. the superior and lnferlorlablal arteries combine to form an arterial clrde around the mouth. The tem!too/ brunch of !he fildill artery. the ar~gular artery, ar~astomoses with the do~l r~asal artery. The latter vessel rs the b!rminal branch of the ophthalmic arb!ry, wflich arises frvm the intern<~! ~rotld artery. Be~use there are extensive arterial aNstxJmoses, fadal lnjur1es have a tendency to bleed profusely but also tend to htill quickly and well CIWI'ng to the copious blood supply. The pulse of the facial arb!ry is p;alpable at the anb!rioc- border of the masseter muscle inM!I'tlon on the mandibular ramus. The prlnclp.;~l br~nc:hes of the post;11rtor aurlalllr artl!ry lndude the postl!rtor tymp.;~nlc artery and the p.;~rotld artery(b).
56
ophlhalmlcartsy
Allrfculr branch
Pastl!t!or aurfculllr amry
Postl!rfor tymp;nlca!Ury
P.lrotldbl'llnch _ _ _..,...,..
Extl!mll - --+unlddutay
'-fll
Het~d - -
l. IJioodVesselsof~HetldandN«
Donal llngl.lillbnonch!s Ung.~~lartsy
;;r:TW-= - - Supr...,.,lcl lnndl
I.'
Emnwl
r>--- - o\JI:endlng plwryngiOIIIIU!y
1
12ra!dar11try
Superior
t¥oldansy 0 U'lgial1rtery 1nd lb llnnches Left lmral view. The lingual artery is the second anterior branch af the emrnal e<~rolfd artery. It has a relatively large e<~llber, providing the tongue with Its rich blood supply. It also gives offbr.~nche.s IDifle plexus arid tnnslls. I! Bnndtes flllfle l!llhrMI arattd iilrtery and their 4llsblllut1Dn: III!Rrfar, medial, 1nd pcllhrtar lnndtes with thl!lr prtndpel
di.UIInncha
...........
AntBior ll!nnchlc
• Superior thyroid arllly (see B) - Glandular branches - Superior laryn9"l • rilly -S~e~~b~nch
B Superfar tlryrald 1rtery, 11cmdlng pharyngule!Ury
lnd their lnncha Left literal view. The superior thyroid artery Is typically the first br.~nch lxlarfse from lfle external carotid iilrtery. One of the antafor brinches, It wpplles ltle larynx and thyroid glind. The asundlng pharyngul a!Ury aprings from lfle m~iil sidevlthe ~I carotid il'tey, usually arising aba¥e ltle level of the superior lflyrold artery. The level at wnl.d t a \USe~ branches from the external caroad artery does not neassa rt1y correlate with ltle murae or thewssef.
• Ascending pharyngeal artery (see a) - Pharyngeal branches - Inferior tympank artery - Pasllerlar menlngul artery
C Ort§ln flllfle -ding pharyngeal.-tery:
typlul c.e
end nrf.ntl (after Uppert and Pabst) • In typlol cases (701) the asca'ldlng pharynge.;~l ilrtery arises from the external carotid artery. 11! - d V.ltlnb: The asandrng pharyngeal artery arises from II the occipita I artery (20 I), c the internal c;,rotid <1rtery (8 'l. or d the facial artery (21).
l"'lltlllforllrandlll: • Ocdplta Iartery (see A) - Occlpbl br• nches - Damndlng bnnch • Poarlar auricut.- bro ndl (sftA)
A MlllllliiiY irtary and Its branchas left later.rl view. The maxillary arll!ry Is the larger of tile 1:\W terminal branches of the eXU!rnal carotid artery. IU origin lies deep 11:1
the mandibular ramus (lmport;mt larldmark for loc.ttfng the ~sel}. The maxillary arll!ry
consists of thlft parts: o
•
Myloh1cfd
Mandibular part (bl~~e)
• Pterygoid part (green} o Pterygopalatine part (yell-)
branch
B The two tl!nnl111l bnu~he• of1M o.tenwl c.trotfd 1rterywttfl tfltlrprtndpll brancltes Brandl
o
Inferior alwolarartBy
o
Mlclclle meningeal ai1Jery (see C) Deep auriCular artery AnWrfor tympaniC artery
o o
Masseteric ai1Jery Deep tempontl branches Pterygoid branches Bucal artery
Mandlble,lftth. gingiva (the mental branch Is Its terminal lnnch) o calvarfa, dura. anterior and middle cranial fossae o Temporomandibular Joint. external audltoly anal o TympaniC cavity o
o
o
o
Hard palate Soft palate, palatine tonsil, pharyngeal wall
o
Lateral wall of the nasal cavity, conchae
0
o Nolsal septum
Soft tissues below the zwomatlc arch Scalp of the fore"'"d and 11\!rtex Lateral orbital wall
Het~d - -
r.
l. IJioodVesselsof~HetldandN«
Anlltrtcr supertcr
Dental brandies
•hlealar atfl!ry
Poster1crsopbl branchos
" C S.lact.d clinically lmpolt.lnt bi'IIKIIH crf tt. mulllary <1rlay • Right middle meningeal artery, II left lnhorbltll artery, c right splwlopalatlne artery with Its branches that supply the n.ual cavity. The mldcle menlng1111ll artl!ry paSRS through the fortmen JpinlllSum Into the middle cranial fosR. Despite Its name, It supplies blood not Just tDthe menlngu but al.sotDthe owriylng cal\lalfa. RJJpture of the middle meningeal. artery by head trauma results In an epidural. hernatom.ll (1ft p. 262). The lnfr-tlblartl!ry is a bl"ilnch of the milllillary artery and thus of the external carvtld artery, while the suprilorblulartery (i branch of the ophthalmic artery) Is " terminal branch of the lntl!mil caroUd artery. These vessels provtde a path for a potential a nasmmosls behwen the extema Iand Inti!rna Icarotid arteries. When sewre naJO· ph1rynge;~l bleeding occurs from branches of the sph•opalat.,e artery (a branch of the maxillary irtery}, It may be necesRry tD ligate the maxillary artery In the p~opai.Jt!ne fosR (see pp. 100, 11 o; 1ft
c
also c. p. 61 ).
D Supetflclal bl!mporel wtery Left lateral view. Particularly In elderfy or ca· r:necuc: patients, the oftEn tortuous course of the fTont.J I branch of this vessel can easily be traced across the temple. The wperiiaal
temporal ilrtery """Y be lnwlwd In an In· flilmrnatDry aullolmmune disease (temporal arterltls), which can be confirmed by biopsy of the wssel. The patients, usually elderfy males, com plain of severe headiKhes.
lrgcmatlc:o- - - - - - ''-'
crbll.'llarmy
of----'--..~-
Supert'dol
llompcnl1tfl!ry
59
Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k
3.4
Internal Carotid Artery: Branches to Extracerebral Structures
CAmel!I part
• A SubdtwtslDns of tfle lntl!m;~l arotSd
Ophth~lml(
Anterlor
artl!ty and brandies thlrtsupp~
chorolclilartery
extncerebral strucu.m of tfle heM!
~or
ammunlc&fng artery
a Medial view of the right Internal e<~rotld arll!ry In Its passage thro~~gh the bones of 1he skull. b Anamrnlcal segments of the l'ntl!mal e<~rotid artery ~nd their br~nches. The intemal e<~rotld artefy Is distributed chiefly to the brain but also supplies extr.iiC4!rebr.ill !'e9lons of 1he head. It consists d four parts (listed from bottom to top): •
S~or
l1ypophysQI artery
Cervie<~l p;~rt
• PettoiiS part
• cavernous part • Cerl!llr.al part The petrcus part of the Internal carotid artery (traversing the carotid e<~nal) and the caYI!m· ous part (tr.werslng the cavernous sinus) have a role In supplying extracerebral structures of the he<~d. They gl~ off illddltlon<~l sm.illl branches that supply local structures and are usually named for the are;as they supply. Only spedallsts may be elq)ed:ed to have a detilled knowledge of these branches. Of spedal lm· port.'! nO! is tile ophthalmic artery, which arises from the cerl!llr.al part of the Internal carotid artery (sed).
a Superior view of the right orbit. b Antl!ri~:~r view of the facial branches of the right ophthalmic ar1l!ry. P.anel a shows the or!glr1 of the ophthalmic artery ;at the internal c;arotid artery. The ophthalmic artery supplies blood to the eyeball I~ elf and to the orblt.11 structures. Some of Its terminal br.mches are dlstrlbutl!d to the eyelid and portions of the forebe.
~ar
elt!maklalartl!ly
Anb!riar ethmoldlllrllery
Ophthalmlc:;ll'llery
C Y.15all;ir SIJpply of tfu~ nnal septun left lilterill VIew. The nan! S4!ptum Is another region in which the internal carotid artery (an-
terior ind posterior ethmoidal arteries, green) meets Ute exterN~I Cilrotld artery(sphenopalatfne artery, yellow). A rfchly vasculartzed area ontheanteriorpartofthenanlseptum.called Klessdbidl's arei (blue).ls the mort common site of nosebleed. Since KJe.sselbich's area Is all area of anast.1mDSis, it may be necess.1ry to ligate the sphenopalatine/maxillary artery irldfor Ute ethmoidal ar1l!rles through an orblt.1l.i1pproach, depending on Ute source of the blee
B-- -111-- - Extl!malcaratld ar11!ry
61
Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k
3.5
Veins of the Head and Neck: Superficial Veins
~~--------1~
fugullrveln 1/IT~o:::-"""-'-------- Ext!ern~l
Jugtl~r~~eln
~------~~rw•
).!gular win
..,......'-"'-""""7;>"'\.;;;'---- i i r- - - - - Suplli!Jai)Uiilr
win
A Sup~dll he.ad and nedcwtnund tfll!lr drainage to the bndJloa:ph1lkveln l.cltla!l!l"alvfew. Theprlnclp.;~lvelnofthe necklsthelntemc!ljuguklrwln. whkh drains blood frcm the rntertor of the skull (Including the br.illn). En dosed ir1 the caratid she
62
glon to the subclavian Yetn. ~tie tne arttwtorjugufarmn dr.rlns the supertlclal anterior ned: region. Besides these superficial Yelns. there are more deeply situated venous plexuses (orbit, pterygoid plexus, middle cranial fossa) that are desaibed in the next unit. N~ The superficial veins are most closely rElated to the deep veins In the area oftfle angular vein, with an associated rfsk of spreading Infectious organisms lntncranlally (seep. 65).
8 Owmew of the prfndpill veins In the had ;md neck 1St later.al VIew. Only tile more lmport.lnt veins .ilre l.abeled In the diagram. As at many other sites in the body, the course and caliber of the veins In the he<~d .ilnd nedc are wrlable to a amln degree. except
C Dr.lhJgeofbloodfromthe heid ;~nd neck Blood from the hNd .ilnd neck: Is drained chiefly by three Jugul.ilrvelns:
the internal, exll!mal and anterior jugularveim. These veins h
for the largest venous trunk. The vdns Interconnect to form extensive .iln.ilstomoses, some of wfllch extend to the deepvefns (see A. pterygoid plexus).
Vl!lln
llllgkln lhlned
lll!lallonlhl(tiD deep
anllalfalclle •lm.tnal jugular win
• lnts1aroftllukull (Including the br.-.ln}
• Within the carotid
• ectl!mal jugular win
• Head (supriciaQ
• Within thuuperlldal cenlialfasda
• Anterior
• Neck. poruons of the head
• Within thesuperlldal cerVIcal fascia
jugular win
sheath
pertldal cervlul f.lsda.
63
Hettd - - 3. Blood Vtosselsoftlte HeDd Gnd N«k
3.6
Veins of the Head and Neck: Deep Veins
Superior _ _ ophthamic-.eln
Angularw!n
.l::)l~--
- ----.s-- --ioll
DMp---~~~--=--~~
facial win
, ..,__ _ _ RietnxTJIIndblllf 'Win
a-.....,,_.._______ Emrnal pala!lne'Win ~~---1~1
Jugllu...eln
A Deep veins of tfle helld: p11ef'ftold ple~Q~S left laterallltew. The ptefygold plexus Is a venous network situated be· hind the mandibular ramus between the musdes of mastication. It has exten.s111e confii!Ctlolu 'With the ~djacent veins.
I DMpwlnsoftflehe.Jd: orfllt and middle cnnl;~l fossa left lateral llfew. There are two relattllely large venous ttunks In the orbit. the superior and Inferior ophthalmic vein. They do not run p.arallel to the arteries. The veins of the orbit drain predominantly into the cavemous sinus. Orbital blood can also drain externally vla the angularvdn and facial vein. 8eca~~Se the veins are Y.illlleless, extracranlal bactena may ml· grabe to the Cavl!rnous sinus .ilnd cause thrDm· bosls In that venous channel (see E and p. 93).
64
c-mous
sinus
::c=::..;;r-- - Inferior
ophthalmic win
HeDd - - 3. Blood Vessels ofrite HHd and N«
------;,--,-------7lf - - SUperior
agltt:alslru
-----.;: ,. . - --+-- CGnftuenceof ltlesl'luses
0~~~--~--~----------.
~-4--
enlsslrywil Venous plelaa
TranswM
31nus
a~Wndltle
fa ramen
C Vetnsoftflucdput
ITIISI<~Jm
Concttlr
'f--'i-;$~-
enb:si ry vein
Venous PlflWsof ----"''"----+--~"" the hypoglossal
e---~--- lntl!mal
l!eMCll'lll
Ex!Jemal wm!ml
)lgularlll!!ln
--~-~1--4~~
" -- - - - Ocdplt.ll win
Postenor 111ew. The superficial wtns of the occiput communic.rtl:! with the dural sinuse$ by w;ry of tile diploic 1/dns. These vessels, called emlss.1ry wins, provide a po!l!ntlal route for the spread of Infectious organisms lnt:D the dural slnus;a.
E Venousanntan101!14!n5 partll5 oflnfed'lan • Very lmport;mt cllnlc;llly because tfle deep spread of bacterial Infection from !he fadal
region may result In avernous sinus thl\lln· basi$ (infection lel'ding w clot fanmatian thatmil)'ocdudetileslnus). Bacterial throm· basts Is less common at other sites.
~nlaiVII!IIn
D alnTCII~Importllnt11MC11IIIrm.tl'on· ships Tn the f'adll region The facial artery and Its brandn~s and the terminal bra riCh of the ophthalmic artery. the dorsal nasal altery, are clinically lmpoltlnt ftSseis in the facial region because they may bleed profusely In patients who sust.lln ml~ facial fractures. The wins In this region are clinlcallytmport.lntbecausetheoymayallowlnfectious organisms to enter the cranial cavity. Bacterldrom furundes (bolls) on tfle upper lip or nose may gain access to !he cavernous sinus byway of the angularl/eln (see E).
Conneclllng Vll!lln
Velalsll-
o
Angulan.Wn
• Superior ophthalmic vein
• Cawmous sinus •
o
Veins of palatfne toMII
o
o
Supertldal temporal win
• Parietal emissary win
• Superior sagittal sinus
o
Oaipital win
• Occipital emissary win
• Transverte sinus.
o
Ocdpltal win, posterior auricular vein
o
o
Extemal vertebral wnous plexus
• Candylaremlsury win
Pterygoid plexus, tnferfor ophlhalmlc vein
o
c.wmouulnus •
mnfluena! of ltle sinuses
Mastoid emissary win
o
SigmOid sinus
• SigmOid slnta
65
Head - - 4. Crankll Nerves
4.1
Overview of the Cranial Nerves
A Functional components of the Cl'ilnlal nerves
The twelve pairs of cranial nerves are designated by Roman numerals according to the order of their emergence from the brainstem (see topographical organization in C). Note: The first two cranial nerves, the olfactory nerve (CN I) and optic nerve (CN II), are not peripheral nerves in the true sense but rather extensions of the brain, i.e., they are CNS pathways that are covered by meninges and contain cell types occurring exclusively in the CNS (oligodendrocytes and microglial cells). Like the spinal nerves, the cranial nerves may contain both affenmt and e~rent axons. These axons belong either to the somatic nervous system, which enables the organism to interact with its environment (somatic [ibf!fi), or to the autonomic nervous system, which regulates the activity of the internal organs (visceral fibers). The combinations of these different genera/ fiber types in spinal nerves result in four possible compositions that are found chiclly in spinal nerves but also occur in cranial nerves (see functional organization in C):
C Topographical and functional organlz.atlon of the cl'ilnlal nerves l1mdloall fiber
- E.g., fibers convey impulses from the skin and stnab!!d musde
spindles
• Abducent nervo (CNVI)'
• Somotic efferent
• Facial nerve (CN VII)
• Special visceral efferent (second bronchkrlorch) • Special vlsaral afferent
CieMr.OI vbanla""ralb (viKZral..,nsatlon):
- E.g., fibers convey impulses from the viscera and blood vessels
• Vlsceli11efferent
(porasympathetlc) • Somatic afferent
CieMr.OI vbanl efferalb (viKZromalur function):
- Fiben innervate the smooth muscle of the visc~a. intraocular muscles, heart, salivary glands, etc. GeMr.OI SOIIIillfc effeftnb (oo....to..-funcdon):
- Fibers innervate striated muscles Additionally, cranial nerves may contain special fiber types that are associated with particular structures In the head:
Medulla oblongata
•
VestlbuiOCDCh~or
ne""'(CNVIII) • Glossopharyngeal ne""'(CNIX)
afferent
• Special vlscoraloffen!nt (!lrird bronchial arrh)
• Spe
5p«<;;l somatic afrarents:
- E.g., fibers conduct Impulses from the retina and from the aiKitory
and vestibular apparatus Speml viKZralalferents: -E.g., fibers conduct Impulses from the taste buds of the tongue
• Special somatic
• Vllgus nerve (CN X)
• Special viscoraloffen!nt (fourth bronchial an:h)
- E.g., fibers Innervate striated muscles derived from the branchial arches (bronchiogenic e(ferrnts and branchiogellic muscles) • Accessory nerve
(CNXI)"
• Special vlscoraloffen!nt (fiflll bronchial an:h)
• Somatic efferent • Hypoglossal nerw
B Color coding used In subsequent units to Indicate different
• Somotic efferent
(CNXII)"
llbertypes
D
General somatic off..rent.
D
Special somatic
D
General vl~al off..rent.
D
Special visceral
D
General vi~al
D
General somotlc
66
~nts
~nts
•
of~Erents
of~Erents
Special visceral l!fferent:s
• Note: Cranial nerves with somatic efferent fibers Innervating the striated muscles also have somatic afferent fibers that conduct proprioceptive Impulses from the muscle spindles and other structures (for clarity, not listed above). A characteristic feature of the cranial nerves Is that their sensory and motor fibers enter and exit the brainstem at the same sites. This differs from the spinal nerves, In which the sensory fibers enter the spinal cord through the dorsal roots while the motor fibers leave the spinal cord through the ventral roots.
HeGd - - 4. Ctvniaf Nerws
..
~~~
)/ I o~rynlfW
I
Opllcn..,.
Ill Oallornolar
67
Head - - 4. Crankll Nerves
4.2
Cranial Nerves: Brainstem Nuclei and Peripheral Ganglia
A OVerview of the nuclei of aanlal nerves Ill-XII
just as different fiber types can be distinguished in the cranial nerves (C, p. 66), the nuclei of origin and nuclei of termination of the cranial nerves can also be classified according to different sensory and motor types and modalities. According to this scheme, the nuclei that belong to the parasympathetic nervous system are classified as generolvisceral efferent nuclei, while the nuclei of the branchial arch nerves are classified as special visceral efferent nuclei. The visceral afferent nuclei are considered either general (lower part of the solitary nuclei) or special (upper part, gustatory fibers). The somatic afferent nuclei can be differentiated in a similar way: the principal sensory nucleus of the trigeminal nerve is classified as general somatic afferent, while the nucleus of the vestibulocochlear nerve is special somatic afferent
Somatic sensation
Alar plate
VIsceral sensation VIsceromotor function Somatomotorfunction
• Floor of the fourth vent~de
Somatic afferent
----r'r-----...
nuclear column
(rbomboldfossa)
VIsceral afferent nuclear column
Mator nudll: (give rtse to~ [motor] fibers, left in C) Somatic efferetlt (som1tlc - r ) nuclei (red): • Nucleusofoculomotornerve(CN lll:oyemusdos) • Nucleus oftrochlearnerve (CN IV: eye musclos) • Nucleus of atxlucont nerve (CN VI: eye muscles) • Nucleus of accossory nerve (CN XI, spinal root: shoulder muscles) • Nucleus of hypoglossal nerve (CN XII: lingual muscles)
• Nucleus ofthesolltarytract (nuclear complex): -Superior part (special vlsceralafferents [taste] from CN VII [facial I, CN IX [glossopharyngeal], and CN X [vagus] nerves) -Inferior part (general visceral ilfferents from CN IX [glossopharyngeal] and CN X Ivagus] nerves)
68
developml!nt (after Herrick) Cross-sections through the spinal cord and brainstem, superior view. The functional organization of the brain stem Is determined by the location of the cranial nerve nuclei, which can be explained In terms of the embryonic migration of neuron populations. a Initial form as seen in the spinal cord: The motor (efferent) neurons are ventral, and the sensory (afferent) neurons are dorsal (• dorsoventral arrangement). b early embryonic stage of brainstem development: the neurons of the alar plate (sensory nuclei) migrate laterally while the neurons of the basal plate (motor nuclei) migrate medially. This gives rise to a general mediolateral arrangement of the nuclear columns. The arrows indicate the directions of cell migration. c adult brainstem: features a medial-to-lateral arrangement of four longitudinal nuclear columns (one somatic efferent, one visceral Pffer· mt, one visceral afferent, and one somatic a(frrf!nt). In each of these columns, nuclei that have the same function are arranged one above the other in a craniocaudal direction (see C). The nuclei in the somatic afferent and visceral affrrent columns are differentiated into general and special afferent nuclei. Similarly, the visceral efferent nuclear column is differentiated into general (parasympathetic) and special (branchiogenic) efferent nuclei. This general/special subdivision is not present in the somatic ~rent nuclear column.
HHtl - - 4. C'nJnJGI Nt!lws
Vlsanl OOJiomotor
nudeus
D D
• D D D
~~~~----S~Mn~~ oftr!gemhal n~
!-7.-7------1\kldeuscf !ICIIItllrytract
• Nucleus of ocularnotarn~
VIsa!nil oculcmotarn~us
Somalk efferent nuclei General visceral eiWwnt nuclei
Special vtsceraleffwent nuclei SoiNiic lffefent nudel General visceral ~nt nudel
Special viscnl afferent nuclei
D Ganglll<~nodlted wtth cnnlll111rws Ganglia fill Inti) two main ull!gortes: sensory .and aLI1llnomlc (parasympathetic). The seMOry gangla are analogous to the spiBal ganglia in the dorsal roots of the spinal cord. They corttiln the perfkaryi of Ute ps!!l.tdoonlpo/ar nerve cells (• prlm.ilry affermt neuron). Their peripheral proce.ss comes from a receptllf, and their cartral process termlnat1!s In the CNS. Synaptic relays do not occur In the sensory ganglia. The autDI*I'IIt §IIIQIIII In the head are entirely parasympathetic. They contain the peribrya of the multipolar nerve cdls (• second efferent. or postsynoilptlc. neuron). Unllki! the sensory ganglia, these ganglia synapse with parasymp;rthetic fibers from the brainstem (-first efferent. orpregqng/loolc. neuron). Specifically they synapse with Ute periiGirya of the second tfi'el'ellt{orpcstsyntlpll'c) neuron, 'Who.s.e fibers .ilrt' distributzd to the target organ.
..
cndlll
,_
feiiiCIIJ
....1..
Oculomotor
Allllan-lc
• OhiiiY 91191on
nerw(CNIII)
ntgemiM
......
• lltgiiNNII
neNe(CNV)
ll'ngllon
l'lldalnene {CNVII)
• c.enlcUa ganglion
·~ palatln~ 91191on • Subman· db...., ganglkln
Vesllbu'dllearnene {Oil VIII) b
a-
pharyngeal
c
loc.ltSonofcnnllllnerws 111-XIIIntfle bnlnlltem ;a Posterior ~ew (with arebellum removed). b Mlds.1gltbl section, left laterill view. El(t;ept for aanlal nerves 1and II, 'Wfllch are extznsions of the brain rather than true nerves, all palrl of aanlal nerves are aJSoclilted with com!spondlng nuclei In Ute brilnstem. The diagrams show the nerve patilways le
ID .mel from tftese
nudel. The arr.ilngernent of the cranial netW! nuclei is easier to understand wltm we dmlfy tflmn Into funct!oBal nudear columns (see B). The effrtmt (motor) tN.Idel vmere the effmttt tlbers .ilrtse are shown on the left side in •· The of(mm (stnllll)') nudei wheretlte~rmtflbers end are shown on the rfghtslde.
nerw(CNDQ
• Splnll
ganglion • Vesllbulr !l'nullon
• SUp!Jior ganglion • lnfellor (pelroMI)
ganglion
~
(OUQ
• Supaior
auaullr) ganglion • lnfellor
• I'I1Mrtl!bral and
Intramural ganglia
(nodOJe)
ganglion
69
Hettd - - 4. CIVInhJI N«ws
4.3
Cranial Nerves: Olfactory (CN I) and Optic {CN II)
t~--~~~~~~~~-----0~~~
tract ·~~:::;.........,..~----- P~rtfonn a~a·
Sernilunar gyrus Am~M~--~~~~~._--~
gyrus
A Olt.u:tory bulb ~nd olt.u:torytnlcton the biNisurfiiC& ofthe frontal lobes ofthe brain The unmyelinated axtuu of the primary bipolar sensory neurons in the olfactory mUCO$a ~re collected Into ~pproxlmately 20 flber bundln (see B). which ire referred to collectively as the ol(rnwy ni!M'. These axon bcmdles PiSS from the nasal c.1111tythrough !he a1brtform plate of the ethmoid bone into the anterior cranial fossa (see B), and synapse in the o1fodtKy lxlfb. The o1(llcttKy lxtlb ind ~S50datl!d o1fodtKy 1n1tt are not pi!rts of a perfpherill nerve but Instead constitute iln extension of the tl!lencephalon thit conulns CNS-speclftc cell types (ollgodendrocytes and micn:.glia). The olf.actory bulb and tract share with the telencephalon~ menlnge<~l covering that Is remcwed here. Axgfu from second-order afferent neurons In the olfactory bulb PiSS through the olfactory tract and medial or lateral olfactory stria, ending In the cerebr;al cortex of' the prepiriform area, in the amygdala, or in neighboring are<~s. By this short route. olf;act:ory Information Is thus tr.lnsml1:t2d Into the CNS and can be rel;ayed directly to the cerebr;al cortex.
I Extent of theolt.rdory muGII5il (olfactory regiDrt) PDrtion of the left natal septum and later.al wall of the rfght nasal c.Mty, viewed from the left slde. The olfilctory flbers on the septum and superfor cnncha define the extent of the olfactory region (2-4cm2). The thir1, unl'!lyl!!li· natl!d olfactory fibers enter the skull through the a1br1form plate of the ethmoid bone (see p. 27} ilnd PiSS to the olfactory bulb (see illso pp. 116, 204, and 372).
70
The primary sensory neurons of the olfactory mucosa have seYeral unusual properties thit should be noted. These neurons have a limited lifespi!n of up to several months, but are continLJOUS!y replenished fn:Nn ~ pool of precursor cells In the olf~ctory mucosa thit undergo periodic mitosis. New olt.rctory receptors ire thus generited throughout adult life, ;and their axons enter the olt.rctory bulb to fonn new synapses with existing CNS neurans. The regenerative capacity of the olf.actory mucosa grad~lly diminishes -Mth ~dvanclng ~ge. '-ever, mulling In ~ net loss of receptors and a slow decline lr1 overall sensory function. Notl!: injulfes to the cl1brltonn plate may damage the menlnge;al cove!'· ing of the olt.rctory fibers, resulting in olfactory disturb.'!nces and cerebrosplml fluid l~kage from the nose (•runny nose• after head triluma). There Is iln associated rfsk of ascending bilcterlal Infection causing meningitis. • The shaded structure5~redeeptotheb~l surf.lceofthebraln.
Rontalsinus ~~~---7~----~~~
flbe's
~~-01br!fonn
pw
s~
co nella
HHtl - - 4. C'nJnJGI Nt!lws
0~~------~~~~~~~~~~
cN'asm
O~lt ----..;:-;=--~~----:i ~rt
uan1--~~~~~~~
genial me bo6f
O~lt
---......:,;_+-4
radatlcn
c Eye. opCfc nerve. op1kcfll..1n. Mel optk tract
VIew of the b;n:eofthebriln, b ~roli!teralvlewofthe leftsldeof ttle brilnstem. The termln..tton of the optic tr.rct In ttle liltl!ril genlculatebodyluhown. The optic nei'Yt' is n~t a true nei'Yt' but an extension ~f the brain, in ttli$ case of the diencephalon. AnalogouJiy to ttle olfictory bulb ind tract (see A), ttle optic: nerve Is she.11fled by meninges (removed here) ind contains CIIS·spedllc eel~ (see A). The optic nei'Yt' conurns tile ax.ons of retin..l ganglion all,, Thae- tenninatl! mainly in the lateral ge· nlculate body ofttle diencephalon ind In the mesencephalon (superior collfculus. pp. 234-235).
;a
~ Because ttle optic nerve ban exteru1on of the brain. the dlnlclan can directly Inspect a portion ofthe bralnwllfl an ophthalm05cope. This examination Is lmportlnt In the diagnosis of manyneurologlcal diseases (ophthalmoscopy is desaibed on p. 133). The optic nave pams from the eyebill throc.~gh the optic canal Into lfle middle aanlal fossa (seeD). Miny. but not all, retinal cell ganglion axonsaouthemldllnetottlecontralater.llsldeofthebr.~ln lnlfleoptlc chiasm {a). The optic tract extl!llds from ttle optic chiasm to ttle lateral geniculate body (see al'o b).
D Courseoftheoptknervelnttleright orbit
l..ab!ral11iew. The optic ni!M! extend!> through the optfc canal from the orbit Into lfle middle cr;mlai fossa. It exits !he posterior side of the ey.!ball within the retro-orbiul fat (rem
71
4.4
Cranial Nerves of the Extraocular Muscles: Oculomotor (CN Ill), Trochlear {CN IV), and Abducent (CN VI)
Ctnbnll pedlndes afmHeNII!pholan
Trodllarni!M!
I
7 ........
~ ~-...,....-- oaJamalalll!nle
L--. ~ ~ rJ -~~amr
Nudetauf--
rudeus
tnxl!INr neM! Nudeusaf
PDns------
oculomotor
Cenll'alg.y ---?'--- ~
sub.mnce Rednudeta -+----1:s..a.t:.~
Nudt!us af oa.lamaiDrneiW
_ , __ _
n9~
C TepegNphJ alttle . ulamolllr nuda~~ Crcn:s1ectlon through the bralnstem at the le"RI of the oculoll'IOblr nucleus, superlor view. Noa: the vtscerill etrl!11!nt, pui1Sympathetlc nudflilr mmpla (\llscerill aa~lomatDr [Edinger-Westphal) nucleus) can be distinguished from the somiltic efferent nudeu complex (nucleus of the oculomotor nenll!). D Onnllewafthetroc:hiHrnerw(CNIV)
A lmq111a1 oflha IMIWI from lha bnlnst.m Almlior view. All three nerves that Sllpply the extnoculilr muscles emqe from the bralnstem. The nuclei tA the oculomotor neM! and bodllur neM! al1! located in the midbrain (mii!.MftCephalon), while the nucleus of the ibducent nerYe islocmd In the pons.
Tlw trochlur nerw mntalns ..,1y samaCir ljjlnntflbers.
c.u.... The troch._r 111M! emqes from tlw post2r1orsurflce of tlw brainsl811 n•r the midtone. c:ou nes anblriarly around the cerebral pedunde. and enlln the arbtt through the superior Ofblbl lluln. ~,__
NIX Of lttese lttree nerRS. the oculomotor (CN Ill) Is ltte only one thilt c:onUins somitlc elfaent 1nd visceral effel1!nt flben ilnd supplies _..II!Xtnoculir musdes (see C}.
• The trochBr ,.,..Is the onlycranlalnerwlnwhlch al the fibeR auutothe opporlle side (see A). Consequently, lesions rlthe nudeus or of trbers 111ffY dose Ill the nudevs, before they CTOSS
The aa~lomatur nerw c:antllns JCIIJICIIIc~ond..., ~ ftbers.
the midline. result In l»chlar niii"W polsy on the side opposltlt to the lesl.., (c...trlllltiorll poll)?. A lesion post the sltltwhelll! the I*W crosses the midline lelds to tochlel r nerw polsy on the Ymt slde as lhe lesl.., (lpollo...,l p1ll}?. • The trochlftr NMOislhe only cronlal nerve lhateme.,.a from the donal side of the brolnstem. • It hu the longest lntradu ral course of the three extraoculor motor nerws..
CounE The nerw n~ns anterlortyfnlm the ,_,aphal.., (midbrain - ~ llwl of tt.. brmstem; see pp.ll6. ~ll) ond enters the Dfblt through tt.. supe!lclr Oltlltlllssln
In the mlclbrillh (rneSI!KepNion).lb effeoentssupplymolllriiiNI'" votlan to one musde. the superlar abllque.
NJCIIus) rn the midbrain ($etC) supply tlw follOWing muscles: - IMIIDr palpebrae superlorts (acts on the upper l)'lllcl) - Superior, mecllal, and Inferior rectLB and lnfwrlor abllque (• ..ct:raaa~lar mLBdes, 111 act.., the .,.._IQ. • 1llsa!RIIefl"r.m*: Para. .piltho!dc preganglionic liffe...,b from the Vls09l orulomotor (Edlnger.-stph•O nucleus syllilpse with nturons In the dllary ganglion that In~ the following lntnoDOJia r muscles: - Puplllory sphincter - OllarymLBde
ElllctsofLillll lar_....., ClallomoiDr polsy. .....-1tr clepenclng on the atlnt rl the fr+lry. • [ffo!cts "'~ CIClJiandDr polsy (JanlyJis rltt..atracxubr tllld lnttaociAr musdes lind ltwtDr Pll pelne): - P!Dsls (drooping oftlwlld) - ~rd ilnd lawai gne devlltlon In the 6ctld eye - Dlplopl• (In the absence of comploc. ptmls) - Myd rl1sls (pupil dOllied due !llsphlnc!B" puplll•• paralysll) - Aclalm modiltiOn dlfllcultleJ (dlllry PI rolysls - lens cannot focus).
72
Nudeu• end
.llll....
en:The nudeus of the trochlur nerwlS locillld
SfKtloftrocHelw-t.turY: • The olffec* .,_ is higher lind is also devilled medially becalM the Inferior oblique (nap..,slble far elwalon and abduction) bealmes dcmlnant due to lcm of lhe superior oblique. • Olplopll.
E OWntTewaftheallduamtnerw(DIVI) Tlw abductnt nerw mntains only IOmGCic efjlnntfibers. Cllurwe Th• nerw foiiCJWS 1long f:IC!nJdclral pilth
btfln ~n'*lng the
orbit through the supertor orblti Itlssure. lllllciluiiiMI........_ • The the abdua!l'lt- is laaled in the pot\S (· midlewl bralnslam). lts fliers emor9ng Itthe lrRrior bonlor"' tho pons. • Its efferent fibers supply 110m.Jtamotarlnnerftll.., Ill a single muscle, tlwlilteral rectus.
nucleus"'
m.tsai.W-.1: nerw hiJirr: • The olffedled •Is d~ medially.
F CouniC olthe nerves ~pplyfng the ocullr muscles Lab!!"al ¥lew. Right orbit. ;a Lab!!"al ¥lew. b superior view (opened}. c .antenor ¥Jew. All three cr.anlal nerves leave the br.il!nst4!1Tl and enter the orbit through the superior orbital fissure, passing through the oommon tendlriOUS ring of the extraocular musdes. The obdUCJIIIt nenoe has the longert fXt10dcHol oour5e. Beci~R of this, abducent nerve p;~lsy may deYelop lrl association With meningitis .ilnd subar.ilchnold hemonbage. Transient palsy may even occur in cases where lumbar puncture has caused an excessive full of CSf pressure. with descent of the bralnstem exerting tractlor1 on the nerve. The oculomotor tterYe supplies p;~ra-
;a
n!dus
Abduc.nt ni!NI!
lnfi!tfor obtque
sympathetic lnr~ervatlon to Intraocular muscles (Its parasymp;~!hetlc flbers synapse In the ciliary g<~ngllon) as wdl as somatic motor lnnl!f'vatlon to most of the extraocul.ilr muscles .ilnd the levatDr p;~lpebr.ae superioris. Oculomotor nenoe p;~lsy may a!fl!!ct the parasymp;~!hetic flbers e1!.CI11!l¥ely, the somatic motor flbm exduslvely, or both at the same lime (seeS). Because the preganglionic p;~rasympathetlc flbers for the puplllle directly beneath the epln~rlum .after emerging from the br.airutenn, they are often the first structures to be aft'ectzd by p~H sure due to trauma, tumors, or aneurysms.
73
4.5
Cranial Nerves: Trigeminal (CN V), Nuclei and Distribution
Ophthimk dlwlslon
lll...ntll!phdcnudeus of trlgomll'lill nerw
T=~=~
f
M..tlr.ry--dlvlllon
Mlndllulir - - --...., dlvlllon lllgemnol.....w
1
'
./~
-rnucloulof
trlgomlnolnl!fW
Prind~(po~ne)--
t~nsorynudOUid
trlgl!llllntl ni!M!
Spnalrudeus - - - of trlgemklal nerw
A Nuclellftd emergence from the pons. Anterior view. The lilrga' sens«y nude! of the trigeminal nene are d151Jfbuted along the bralnstem ;md tldl!nd downward Into the spinal mrd. The sensDf)' root (major p;art) of the trigeminal nervi!! thus farms the bulk of the fibers, while the mofDr root (minor p;~rt) b formed by fibers arising from the small motor nudeus In the pons. They supply motor lnnervolllon to the muscles of mastlatlon (see 1). The following .somcrtic~ nuclei are distinguished:
frum the muscles of ma.tic;ation. Spedal felt!J re: the neurons of this nucleus are pseudounlpolar ganglion cells that have migrated Into the brain. • PWndpol (pontiMJ JI!I1Sllf)' nudftlS of 1M 17igrminol nl!l"ll£ chiefly m~lata touch.
• Spinal nudeus a{ ltle trlgemlno/ nww: piln and tempenture sen· solllon, aiJio touch. A small, drcumscrlbed lesion of the trigeminal spinal .nsorynudeus leads to charad.eristic sensory disturbances In the fKe (see D).
II Cross-section through the pons at the level of emergence of the trlgemlna I ne~ superior view.
74
8 Onnllewaftlw trfg~mtn~lnerw (CN V)
The trigeminal nel"ft, the sensory nel"ft of the heild, mntalns mostly SGIIlm1c affw1nttlbers with ll smaller proportion of special viJcfral ~fibers. ItS thrMINijor somatic dhlsr- hM! the following slls ,., .......... from the middle aanlal fosu: • CJp/IIIIDimlr:dMrklll (CNV1j: enll!rsthe orbltttuaugh the superlDr Drilbl ftssuN. • ~dflmloti(CNV:}:cntmthe ~bHthrough
thefofanwn roeuncllm. • .........ciMoion (CN V,): passes through the flnmen cw•ID lhe lnfe!lar surbm the bne of the slcuH; only division a>nt.lnlng matDr ftben.
m
Nuclei •d dlllrloullon: • Sp«1ttliii$CIIOI effe'r!nt: Efflrent flben from !he rnoiDr ru:leu1 of lhe tJfgemlnal ntNt PISS In the mandibular dMslDn (CN vJl tiK
- Musdes of m.tk.ltlon (tempor.~lls, m~~sseter. medlllland lllllnl pt2rygold) - Or1l ftoor musdes: rnytoh)'oid and anll!rior bellymthe divastric - Middle .. r mUICic IB110r ~p;~nl - Pharyngal musclr. mnsor wll palatfnl • SomG~aj!Wnnl: The trtgemlnal ganglion contillns pseudounlpola r gingllon cds wt.e c.ntra libel'S pass 1111 the Sl!llJOfY NICIII of thetlf9l!ntiii1M1W (see A e). Their~~~~ flbtn 1r1nerta the flcial sllin• ..,. portjciM Ill the IIISOpNryngeal fi\UaiiSI, and the ....artor~ rlthe langue (somlllk sensation,- Q. • "~~~Jan! rffa'«rt paiJrwat': The viscera Ie!ment llben of Mimi! aanra Inel"ftl adhere to branches or sub-br.lnches of lhe trlganiMI nerw, bywhkhthey tr-1 tothlllrdestllllllon: - The lacrliNIII'IIM! (branch of CN V1) mnveys p;~raympilhllllc fillers from lhe facialnerw along the z,gomatic nerw (br1 nell m CNV2)111thelac:rfmalgland. - The aurlaolcamparalnerw (branch of CN V,)
•
~ offolrrM,..,_,.,~~fnlm the bclalrww (
D•
1ID•~Iy. the tngemlnal nenoels the ner;e llftne llrJt
br<~nchllllan:h.
CIIIIQII dl_.,.. llfdle.......rn.t-: Sensory dlsturba~eS lind defiCits may arise rn var1ous mndrttons: • Sensory loss due Ill triumattc nerwleslons. • Herpes - •ophthalmicus {iiWOiwmentof the territory of the fint division !lithe tngemlnal nerw,lndudlng the skin and/or the ~~p, by the var1all..--ter virus); herpes zmter df the fac:a. The afferent ftbers mthe trigeminal neNt OIIIR the fadal neNt, seep. 7t) are rrwoMtd In the ami!OII'fl*(rellex dDM!ne mthe e)'tlld; seeC.p.l&1).
HHtl - - 4. C'nJnJGI Nt!lws
OphthalmiC
----~__.
dMilon {CNV,}
b
Mandibular----"dMslan(~~
•
II
C CourM ;~nd dlltrtbu\lon ofl:he trfgemll'lll nerve • 1St lateral view. Thettlree dMslons of the trtgemiNI nerve and cllnl· ally lmport:lnt termiNI branch~!! ~re shclwn. All thrn divisions of the trigemin~l n~ $Upplytt1e skin ofttle face (b) and !he mucosa of the ni150pharynx (c). The anterior ~1hlrds of ttle tongue (d) receives sensory lnneNatfon (touch, pain and thermal sensation, but not taste} via the lingual nerve. which is a branch of the mandi· bular dMslon (CN V~. The muscles of mastication ~re supplieod by the motor root of 1he trigeminal nerve. whose axons artier the mandibular dMslor1(e).
NotJt: The efferent fibErs courJe eXA:Iuslvely In the mandibular dMslor1. A perlpheroll!fgemlnal nerwlfslon lnwMng one of Its dlvlslons-ophlflalmlc (CN V1). maxlllary (CN V1). or m~rldlbular (CN V3)-may cause
loss of $CNTI~tic ~n~tion (touch, pain, and temperature) ir1 the a~ lnneNated by the afferent nerve (see b). This contrasts with the more coocentrfc pattern, and more restricted modality, of sensory deficit prodUCI!d by a central (CNS) lesion inwhling trigeminal nuclei and pathways (see D).
D eentnl trfgemlnllletlan
Principal (pontine) sen50fY nucleus of tile trigeminal nerve
•
•
a Somawtoplc organization of the spinal nucleus of the trigemiNI nerve. b Ficlill zones In 'Which sensory dellclts (palrl
Sl!lderlints
A Bn1nches ofthe ophtflalmlc dMikln (• ftrst dMIIIon ofthe trTgem11111 neM!, CN V1) Tn the orblbl region l.ater.ll view of the part!ally-clpmed right orbit. The first small lmmch arising from the ophtftalmlc dllllslon Is !he recurtent menlnge.;~l branch, which supplies sensory lnnewatron to the dura mater. The bulle of the ophth
Noii!:Thelaafmal nerve receives postsynaptic, par.asymp;llhetlcsecretomotorlibets from the zygamatic nerve (maxillary divisian) via a mmmu· nlarlfng btonch. These flbcn triVd to the lacrimal gland by the lacrimal nerve. 5¥mp;ltftetlc flbers accompany !he long dllary nerves that arise from lhe nasodllary ne~W, tnvelrng In these neNes to the pupil. The ciliary nerves ai5CI contain afferent fibers th
- - -·-E::- =ir--.-1-i--iiii-- - Z)'!JCINit'lc:nerve
B Bn1nchesofthe mlldlllrydMIIon ( · - d dlwtllonoftfle trTgem11111 nerve. CN Ya) Tn the mlldlllry regTon Lateral view of the partially opmed right miiXIIIary sinus with the zygo· matte arch removed. After giving off a me11lngeal branch. the maxillary dMslor1le.aves tfte middle cranial fossa through !he foramen rotundum and entl!!ts the pt2rygopalatine fossa, where it divides into the fallowIng branches:
• Zygomatic nerve • Ganglionic branches to the pterygopalatine ganglion (sensory root of the pterygopalatine ganglion} • lnfuaorbltll nerve The zygomltk nerve enb!rs the orbit through the trt(MorotflJt:/11 (lssiJI'I!. Its two temninal branches, the zygomilticofucial branch and zygomilti·
76
~~~"""71-----,~---
lnfr.JortJit.llne
""-:l~---!+.....::.--=::----
Alm!r!arsuper!or ah'eoln brlii'ICtle
cob!mpor~l branch {not shown here}, supply sensory lnnewa!Son to the skin CM:!r the zygomatic arch and temple. P;arasymp;llhetic. pomynaptlc flbers from the pterygopalatine ganglion are carried to the lacrimal nerYe by tfte communicating branch (seep. 81}. The preganglionic fl. bers arfgrnally artse frcm lhe f.adal nerve. The lnfraartlrtal nerw also passes through the inferior orbit!! fissure into tlle orbit, frcm which it artm the lnfuaorbltll canal. Its fine temnlnal branches supply tfte skin between the lower eyelid and upper ltp. Its other terminal branches form tfte Sllpl1lar denflll plexus. 'Which supplies sensory Innervation to the maxillary teeth:
• Anterior superior alveclar branches to tfte incisors • Middle superior alveolar branch to lfle premolars • Posterfor superlor alveolar branches to tfte molars
HHtl - - 4. C'nJnJGI Nt!lws
'Mge
ganglion
Mandibular dMslcn
Foramen
DHptl!mporal
cwale
ne
=~-----.,....-,:--',.....--
Patygoid
n-.s
C
BI'IIIIICMI ofthe mlndlbullr dMslon {•thin! cfi'IITslon of the trTgemln~~l nerw. CN In the m•ndlbul•r region
v,)
Right lateral view of !he partially opened mandible wllh !he zygomatic arch remcwed. The mixed ifferent-efferent ITiilndlbular dMslor~leaves !he middle cnnlalfossa through thefor.amer1 ovale .and enters the Infra· temporal fossa on theextemai
The branches of!he oudailomnporollleM'supplylhewmporal sldn,lhe extem;tl auditory canal, and the tymp;lfllc membrane. The flngtJal tlfM! supplies sensory ftben to the anterior two-thirds of the tongue, ind gustatory fibers finam the chorda tymp;~ni (facial neM! branch) travel
with it. The offrnnt fibers of the in(rtHlr oflilt'Olar ni!M! pass through the mandibular foramen Into the mandibular canal, where they give off Inferior dent
Ma5SCUric nerve (mmetel' muscle) Deep temporal nerves (tempor.tlls muscle) Pterygoid nerves (pterygoid muscles) Nerve ofthetensortymp;~nl muscle Nerve of the tensorveli pal<~tini musde (not shown)
D arnkll1nenmcnt oftrtgcml'nll nerve functfgn £<1ch of the lhree ITiilln divisions of the trtgemlnal nerve Is tested Rp;trmly durtr~g the physical examination. This Is done by pressing on the M1lo'l! j!J(jtpojiltswith onefingertotest !he sensation there (ICI(al tendernus to pressure). The dtaractmstlc nerve eJCit points are aJ foii!MJ:
Cranial Nerves: Facial (CN VII), Nuclei and Distribution
8 Overvtewofthet.ldalnerve(CNVII) The fldal nerve mainly
angle between the pons and ollw.lt passes Ulrough Ule Internal acousuc meatus Into Ule peCrous p;rrt of the temporal bone. whlft It dNicles into its branches: • Tbe vlscleral effeiWit flben pass Ulrough the sc,lomosloid (!nmel liD the bllse of the skull to fonn the lnt111parolld plexus (see C). • Tbe paraymp;~theUc. v1sar111 efferent. and V1sce1111 afferent fibers p;ass Ulrough the peO'Oiympl/lllc jlmn'tto Ule base of the skull (see A. p. 80). WhAe still In Ule peCrous bone. Ule facial nerve grws off the g - petrosal nerw. stapedial nerve. and chorda tympani.
/
Nudeur. of solitary tr.act
• J\bducert
Internal genu
nucleus
offlldlln~
Fact~I
nucleus
A NuclehndprlndJU!I br~~nchaoftheflldlllnerve ;a An!l!rior view ofthe br;rlnstem. showing the site of anergence ofthe
fadal ntn'l! from !he h:mer pons. b Cross-section through the pons at the level of the internal genu of the f.lcial nerve. Nok: e;rch of!he different fiber types (different sensory modalities) Is associated with a p;rrtfcular nudeus. From the flldll nLJCiars, the spedal!lfSa!«ll ~ axons tbat Inner· vm the muscles of facial expression first lt!Cp backward around the abdu~nt nucleus. where they form the Internal genu of the f;rclal nerve. Then they run foiWilrd and anerge at the lowe!' border of!he pons. The tuper'lar s.n111tory nucleus ccnt.illns IIISa!romOII:Ir, presynaptic porasympml!mc ne.Jroru. Tog ethel' with ~ (• gurt.alllry) fibers from the nucleus of the solitary tr.1ct (Mrpafor p;rrt), they emerge from the pons as the nerws Intermedius ;rnd then ;rre bundled with the 1IISt:l!nWo!DI' .axons frcm the facial motor nucleus to together form the fadalneM!.
Nuclei •ddllelllulloft. gong/lo: • ~ IIIICMII t/flrtnt: Efferents from Ule fadil nudeus supply the following muscles: - Musdes of facial U!ftSSion - Stylohyoid - Postmorbelly of Ule dlgastrk - Stapedius (stapedial nerve) • lliKBvJeffetent~: Paruympathetk presynar> tic flben •rising fnlm Ule superior saiMitory nudeus synapse with neurons In thep~ ganglion or sullmandlbulatpg/IM. Tbey lnnentatethe follOWing str\Jctures: - I.Jcrtmal gland - Small glands of Ule nasal mucosa and of Ule hard and soft pellte - Submandibular gland - SubllngL~<~I gland - Small sal!vlry glands on the dGr$Um of the tongue • ~ IIIICMII G#fffWif: Central fibers of pseudounlpolar ga~ gllon cells from Ule tenlculate ganglion (corresponds liD a spinal ganglion) synapse in Ule nucleus of Ule solilllry lract. The peripheral proC2SHS of these neurons fvrm Ule dlotdD t,mpani (gusbtDry fibers from the antmor two-thirds ofthe IIDngue). • Somcrl1c Cl/fftrnt llfC81)I)SI Some sensory fibers that supply the aurtde, the skin of Ule auditory canal. and Ule outer surface ofUie tympank membrane tr-1 by the fldal nerve and gftlku/orltgong/loll to Ule trigeminal sensory nuclei. Tbeir precisecourte is unro-n. ~Jy. Ule facial nerve Is Ule nen~eofthesemnd
branchial arch. ar.ctsGft.daiiiWWI~ury: A peripheral f.ac:lalnervelnjuryls chlrx-
terimd by pa111lysls «the muscles «expression on the alfedal side of the f<1ce (see D). Because the facial nerve conveys var10us fiber co~ ponents Ulat lefte Ule main ttunk of the nuve at different slw. the clinical ~n offaclill p;~ralysls rssubfediiD subtle varlilllfons marlil!cl by assoc:ilted disturbances of taste. lacrimation. salivation. ek. (sed, p.80).
78
HHtl - - 4. C'nJnJGI Nt!lws
~;..-o=-==---
Postl!rfor
aur!culolrnerwe
flldalnene
C F•dlll nerve bnlndlet (or the muKiet of expression
Norelfle different flber types. This unit focuses almost exdushlelyon the vlscfral ef(rrettt (branchlogenlc) tlbers for the muscles« facial expres· 51on. (The otilerflbertypes are clescrlbed on p. 80.) The mpedi~l nei'Yt' (to the Jt~pedi~JS muscle) branche$ from the facial nerve while sdll In the petrous part of lfle temporal bone and Is men· tloned here only because It also contains 'Yisceral efferent fibers (lt:s course Is shown on p. 80). The first branch that arises frcm the fadal nerve after Its emergence from the scylomiiStold foramen Is lfle poswrtor urkular nerve: It supplies 'lfsomll f/fm!nt flbers to the posterior auricular muscles and the postelfor belly of the ocdpltofrontalls. It also conveys Somall:l.ltnsOI}' fibers from the eldl!rnal ear, whose pseudounl· polarnei'Yt' cells ;~relocated in the geniculm! ganglion (seep. 80}. AIU!r
D Ccntnl•nd pcrfpheRII hdll piRI!pb • The facial motor nudew contains the cell bodies of IOIM!r motor neurons .,mlch lnDei'Vate Ipsilateral muscles of facial expressloD. The ~ (special 'Yisceral efferent} of these neurons neach their musde
le;nting the petrous b~ne. the bulk of the remaining viscer;~l efferent fibers of the facial nei'Yt' form the ln\l'llpilrGI:Icl plaxw In the parodd gland, from 'Which successi'Ye br.-anches (t!mporot zygomattc. bucml, .-and morgiiK/1 mondlbulllr) .ilre dlmtbuted to the muscles of faclalupresslon. These facial nerve branches muJt be protected during the removal of a benign parotid tumor In ordes to preserve muscle funcdon. Additionally. there are even smaller branches such .-as the digastric brilnch to the posterior belly ofUie dlgastlfc muscle and the stylohyoid branch to the stylohyoid musde(notshown). The lowest branch arislng!Nmthe lntr.tparotfd pluus Is the ctMalt brcrlldl. It joins with lfle transverse cer'Ylcal nerw. an anterior br;mch ofthe C3 spinal nei"Ye.
targets through thef.ildal nerve. These motor neurons are lnnerwted In tum by upper motA:Ir neurons in the primary sonnatomot:Dr cortex (pnecentnl gyrus). whose axons enter cordconuclear flber bundles to reich the fadal motor nucleus In the bralnstem. Naf1!: the facial nudeus has a "blpartrte• structure_ ItS upper part suppf>'ing the musde5 of the forehe;~d and eyes (b!mporal branches) .,mile its lower part supplies lfle muscles In lfle lower half of lfle f.lce. The upper pillt «the f.ldalllEn'e nucleus receiYes bllm!r.ll lnnew.ltlon, the lower pillt mntralaterallnlll!lv.ltiOrl ti'om cortical (upper) moblr neullli\S. b Cl!ntnl (supn111ude<~r) pllralywll (loss of the upper motor neurons, In this case on the left side) presents cllnlt<~lly with paralysis of the contraliteril musdes of facial expression In the lower half of the face. while the contr.alater.al forehead .ilnd extra-ocular musdes remain functional. lhU'I, the comer of the mouth $.15IS on the right (contralm!ral) slde,butlfle patient can stlllwrinklelfleforehNd anddoseUieeyes on both sides. Speech articulation Is Impaired. c Pl!ftphHIII (Tnfrlnuc:le.lr) p!11111Jysls {loss of lower motor neurons. In this c.ase on the right side) is c:har~cterill!d by compl~ p.aralysis of the lpsll.-ater~l musdes. The patient cannot wrinkle the forehead. the comer of the mouth sags• .-ardculatlon Is Impaired, and the eyelid cannot be fully dosed. A Bell phenomenon Is present (the eyeball turns upward and outward, exposing the sdera, when the patient attempts to dose the eyelid). and the eyelid closure reflex Is ibollshed. Depending on the site of the lesion, .-addttfonal delldts may be present such as decreased lacrlnnatloD and $.llrv.atlon or loss of taste sensation In the anterfortwothirdsofthetongue.
79
Head - - 4. CrGnltJI Nmlu
4.8
A
Cranial Nerves: Facial (CN VII), Branches
"-daln.,.bnndl.lndw~
IIane l.ab!ral view ofltle right b!mporal bone, petrous portiGI'I (peerous bone). The flldal nerw, accom panled by ltle vestlbulocochlnr nerw (CNVIII, not shown) , p~ses through the lnb!rnal acoustic meaws (not sh-n) to enter the petrous bone. Shortly th~hr It fwms the fJIRmal !lf'IU Df the f.ad.al nerve, which milrts ltle IDation of the gen lal~te ganglion. The bulk of ltle visceral efferent fibers far ltle musdes of expression pi1Ss through the petrous bone and leiM! It .atltle stytomutDid fo~men (seep. 79). The bela! nerve gives off ltlree
RodalntN!
GenlcUate
111g..,t....r
ganglon
nen~t
Htma of aNI for
brllnd>es ~en the genicul;b! ganglion and
stylomiiStold rv~men: • The p;ll'asympathetlcgi"Nt.wpRliNI~WW arises directly at the genku~te ganglion. This nerve INVes the anterior surface of the pelrDus pyramid at the hiatus of the canal for the greater petrosal nerw. It contln ues through the foramen licerum (not shown), l!l1tln the p~ByGold canal (see C), and passes to the pl2rygopalatlne gang lion. • The llbl,_.l n.,. piiSSI!$ to the mUK!e of the same name. • The dlonlll tympMI br.anches from the facial nerw. a'-t! the stylomastoid foramen. It contains gustlltory flbe·rs u well illS presynaptic paruympathetlc fibers. It runs through ltle tympaniC c.vlty lind pelrDtympanic fissure and unites with the lingual nenoe.
1'115t:l!rlor aurttulr lliiW
B Branc:Hng piltll!m Dlthe fildal n~n~~~: dlignllltlc significance In tempanl bane fnctures The principal signs and sym ptDms are different depending upon the exact Jite of the lesion In the course of the faclil nerve through the bone. Note: only the pslndpGI signs 1 nd symptllms assodalled wtth a partleuII r lesion site are descr1bed. 1he more per1ph1K111 the slt2 of the nerve Injury, the II!SS diverse the signs and symptoms become. A lesion at this lew! ~ects the facial nerve In acldiUon to the wstlbulochochl~ar nerve. As al'ftult, periph~r~l motor f~cial par~l)'$iS is
stylomaollald for.alllt'n
5
2
3
4 5
80
iiCCOITlpllnled by he.ir1ng loss (deilfness) and vestibular dysfunction (dtulness). Peripheral motor bclal p~~nlysls Is iccomp~~nled by dlstllrb.ana!s of taste sensation (chorda tympani),laaimation, ~nd saliV
HHtl - - 4. C'nJnJGI Nt!lws
Trfgemlnaii'M!I"IIe
Trigeminal
ganglon
VII axnmo.nlortfng bnuxlltothe
~) -~i:::··~
lnll!mal Cllnltfd artsyv.4th lnll!mal G rotld plexus
The presynaptic, parasympathetic. Vlscer.ill efferent neurons ue located irl the superior s.aliv.atory nudeus. Their axons entef' and leav!! the pons with the v!Ka'al efferent axons iS the nei'\IUS lnt1!nnedl115, then travel with the visceral efferent flben arising from the f.ldal motor nucleus. These pregar~gllonlc p.;~mympatltetlc .axons exit the br.illnstem In the facial nerve and branch fn:lm it irl the greater pelrDsal nerve, then mingle with postgangllon~ symp
palatine, and pharyr~g~l muc:oSi. Abers from this g<~nglton entef' the maxillary dMslor1 ;md travel wllh It to Innervate the taafmal gland. Vtsmal offrrent .axons (gustmlry fibers) for the ;mtetfor two-thirds of the tongue rur\ in the chorda tympani. The gustatDry fibers originate from pseudounlpolar sensory neurons In the gcnlcUite g~ngllon. 'totllch oorrespotlds to a spinal sensory(dorsal root) ganglion. The chorda tympani .illso conveys the pre.synaptk pormympothetlc 1/Jsmal effl!f'fllt fillers for the subm;andibular gland. sublingual gland. arid sm;all salivary glands lt1 the anterior ~thlnds of the tongue. These flben travel Mth the lingual nerve (CN V:s) and are relayed In the submandibular gar~glkm. Glandul.ilr branches .ilre then dlstr1buted to the respective glatlds.
D Nerves of the petrcMlJ bone Great:2r pelrDsal nerve
carotid plexus; unites wtth the greater petroSil nerve to form the nerve of the pterygoid ca~~o~~l, thet1 continues to the pterygopali111ne ganglion .ilnd supproes the same llenitory as the gre~ter petrosal nerve (see C).
gland. ~I glands) ~.esse~' petrosal
Presynaptic parasympathetic branch fnlm
nerve
CN IX. to the otiC ganglion (parotid gland, buwl otndlablalglands. seep.U)
81
4. Cranial Nerves
Hftltl -
4.9
Cranial Nerves: Vestlbulocochlear (CN VIII)
Medial
Wltlbulor nud...
Superior _ ......r
A lludel oftlle..UIIulocochiNt ne,... (01 VIU) Cross~ through the uppe.r medulla oblong~tl. il
nudeuJ
Yetlllular nudeL fGur nudnr complt~~eS 11e distinguished:
• Supesforwstlbu llr nucleus (of Bechterew) • Lab!r.ll wstibular nudeus (of Deiters) • Medlil YeStlbularnudeus (of Schwalbe) • lnferforwstlbular nudeus (of Roller) Nom: The lnfl!rlor wstlbubr nucleus does not appear In a ao:ss-sec-
tiGI'I at this level (see the loation Gf the cranial nerw nuclei in the br~lnmm, p.228). Most of the amns from the vestibular ganglion terminate In these
four nuclei, but a smiller number pass directly through the Inferior cerebellar peduncle Into thlt cerebellum (see~)- The ¥eStlbular nuclei appear as eminences on the flCIOI' Gf the rhGmbgid fwsa (see Eb, p. 227). Their central ccnnectlons are shown In Ea.
• Ploscerfor
nudous
I
Antlorforcochlear nudeus
b Codllur nudel. Two nuclur cornplela!S 11e distinguished: • Anterior cochlear nucleus • Posterior cochll!ilr nucleus Both nuclei are located lateral to the ~~Htlbular nuclei (see All, p. 228). Their central connectiot\S are shown in Eb.
b
B O.rvlnl aftlle ..UIIul-lllurnerw (DI VIU) Thewstibulocochllar nerw is alpftialJOmGCic ll{ftn!nr (sensory)
""""'tNtmnslltunaiDmlully and functionally oftwo mmpol'll!nb: • The II'ISUflular roottn~nsmlts lm pulsu from the wstfbullr apparatus. • The cachl.r roottransmits lmpul,., from the auclltDry app111 rotu..
These raots a"' sunaund.cl by a cammon cannedlve~ue llhe•lh. They PiSS from the Inner ear throuQh the lnternalamustlc meatus to
the onbellopontlne angl1, -Mlert th.,-1ntertM br.illn. Nudeland dlllr1llulton, fG11f111a: • ~root: The mtlbularJJGnri/Son mnbllns blpollr ga01111on
cells -Mlase central proceu. [MIS tD the fourwstlbular nuder on the floor of the rhomboid fossa af th1 medulla oblong•b. Their perlphenl proa:sses begin at the sensory cells af the semicircular canals. sacculi. and utrlde. • CDc~!,_. lOCI: The spital fiiJflg/ton contlins bipolar g~nglion cells whose centlll p - PI" to the two mchlear nude!, which an: Iaten~ Ito the \Wt'lbula r nuclei In the mombold foss.J. Their pe~plt eralpi'OC2Ssubegln 1tth1 hllrcelluftheOigln afCortr. IMry thDrOugh physiaiiXImlflltion should include a n1pid assessment af b~ rww campon1nts (hurlng and lwolonce tests). A lesion af~ vestlbul~r root lelds tD dlrzlnt~t, whl~ a lesion ofthe Clldllelor root lucls tD r-tng loss (ranging to clea'ness).
82
Ce!Selk>-
ponllnnnglo
....,,..'-'ihiF--
Aalustlc
"""""""
('mllbulor Khwonnomo)
C Amullk: naroma In h anbellopGndne 11111le Amustic neuromas (more accurately, vestibular sdlwannomas) are
benign tu men of the cerebellopontlne angle 1rlslng from d-Ie Schwilnn cells of the ¥eStlbular root of 01 VIII.IU they grow, they com press and displace the odjacent structures and cause siCMty prvgre"ive hearing losnnd galt1tlxli. unge tumors an lmpalrtfle egress of CSF from the fourth ventrlde. co1uslng hydrocephalus and symptornaUc lntncranlil hypertl!nslon (wmlting, Impairment of c:onsclgusneu).
HHtl - - 4. C'nJnJGI Nt!lws
Viesabllarganglal\ wpo!l!arp.wt
D Vfltfbulnoangllon ;111d codllen ganglion (splr.llg;~nglla) The Ye.Stlbular root and cochlear RIOt still exist~ sep.arare structures In the petrous part oftheb!mpor~l bone.
flocxulusof -~==--~· arebeilum
hferfar
vestbular nudws
E Nuclet oftfu~vest!Wocodllen nerve Tn the ll111lnstem Antel'for 11tew of the medulla oblongata and pons. The Inner ear aDd Its a~nnectians with the nuclei ~reshown schematicillly.
a Vestllullr palt The vestibular ganglion mntains bipolar sensory ails whose peripheral processes pass ta the sanlclra~lar canals. s;~ccule. aDd utrlde. Their ax.ons travel as the vestfbular root to the four vestibular nuclei on the floor of the mombold foss;~ (further CDnnoectioru are shown on p. 368). The vestibular organ processe.s Information concerning orlentit!on In space. An acute lesion of the vestibular organ Is manifested clinically by dlzzlness (vertigo).
b Coc:hlear put: The spiral ganglia form a band of nerve cells that follows the course of the bony core of tile cochlea. It contains bipolar sensory ails whose peripheral processes pass to the hair ails ofthe organ of Corti. Their centril processes unite on the floor of the Internal auditory canal ta form the cochlear RIOt and are dls!Jfbuted to the 1:\W nuclei that ;me posteriOr to the vestibular nuclei. OUter connections of the nuclei are sham~ oni) 366.
83
Hftld -
4.10
4. Cranial Nerws
Cranial Nerves: Glossopharyngeal (CN IX) lnfslor
Nudo!us aftho IDIItary trxt,
gJivotoly
nudtus
~~ ~daaoftho
Nlldaa omblgws
IDibytrart.
rn&flor JNrt
~t~7~=~ Nudowoftho~ IDhtorytract
-'--""""'
Nuduoftho _ _ _ __..,..,::;.__
solt.lryllact
a-
..
phoryageal neow
A Nudll llfdle11DHOph~l niiW 1 Meduii.J oblongollbl, interior viii!W. Ill O'osHettlon through tbe
medulla oblongata It the 1m~I Clf emergenCie of the glossopharyngeal nerw. Ford.Jifty, tile nudel oftbetrlgemln.JI nerw are not shown (see I for further details on the nuclei).
B Onnl1ew of die IIDUOphlrynglll nMW (CIIIIX)
The glossophlryngul nerw contains pi«UUatrd~ visarol f#ffrfllt,.,_,ln adiltlon tllw!Jtral~tand somattc~tjlllm. 5ltel ..,......,.._The glossophlryngul n•rw •"*VVS from the medull• ablang•to •nd '--• the ~nlal avtty through tl. Jugulor
fo111111181. llb:lel and olllltllutl•, gong/fv: • Sp«jrriiiUcrnl. .(lmJndllogenk); The nude111•m blguus sends Its .1mnsIllthe canstr1ctDr muscles ufthl pl\ar,nx (• pharyng&l lnndlu,joln with thewgus tDform the plgryngeol plalll) and Ill the stylopiiMyngela ( - C).
tbe ]Mr01ic1 gland and ID the bucallnd labW panels(- a and E).
c.ennr procasesd~stnSOIY
• Somcllfr. .
•
c
..
ganglion cells loated in the inf1Ticraniol~gonglion or ~ ln(rJfwgGIIflllon of the ~pharyngul ntn~e tenninate in lhe spinal nudeus oftl.trigemln•l- The perlphtnl prooesses of lhese cell• lrfR from: - the posmricrthinl ofth• tongu•, .soft palm!, phlryngul mucou, .1nd tllnslls (liferent ftbers for the Qlll relle~C). see Ill and c - the mUCOH ofthe tympanic awlly and ellltlchian tube (tympanic plexus). see II - theskln oftill! u~an~lurond audiiDryunol (blends with thl! lwTIIDry supplied by the VIIJUS ntrvt) and the Internal surface of the tymp;onlc membnuw (JNrt ofth• tymp1nlc pluus). • 5p«1(11 ~SICffVI ~ ecnt111l prootSSeS of p$81doun~lor gonglion tills from thl! Inferior gor~~~llon lllrmln•tlln U.e superior p.1rt of the nudeus of the solitary trillct. Thtlr perlph•ral processes orlglnltle In the pos12rlor third ofthe tongw (sjUIUI:Gry ltbers, see e). • \1mnll ~ Sensory flbers f'n)m the following reaptllrs termlnol21n thl! Inferior port of th• nude111 of th• sal!tory lr.Jct: - Chemoreceptllrs In lhe carotid body - P'rasul1! 11!ceplln In tl. a ratld sinus (s• f) O.O.Io,.......rly,theglos$ophlr,nge~lnerwlslhe-oflhethlrd
branchialan:h. Isolated lesloftl of the glaaophlryngul nerw 1111 ral1!. Lesions of U.ls nerw .1re usu.Uy ilccompanled by lesions ofCN X lind XI (va~us nerw .Jnd ;oausory nerw., cnmlll p.1rt) beCIIW.II thrw IWWSeml!lp jantyffom thejugularforllml!lllnd RIll~~~~ lrpyln ~sku~ fractures.
84
HHtl - - 4. C'nJnJGI Nt!lws
Ungual b111nthi'S TymJ)Oilk nerve - -
C lnn!d••oftl!.glph;lrynge;JI nerw beyDnd
Supt!rlor g;Jfl!lllon
1~--='f---
1M tlalll base
lnfe
Left late<;al view. Noll! the close relationship of the glossoph.aryngeal nerve tD the vagus nerve (CN X). The carotid sinus ls supplied by both nerves. The most lmpomnt brallChes of CN IX seen lrl the dlagrim are as follows:
!Jinglon
• Pharyngeal branches: three or four brinches for !he pl\arynge
vagus nerw.
I'Nr)\'lgul plexus
pha~lbranches
body.
• Tonsillar brallChes: for the mucosa of the pharyngeal tonsi1 aoo lts sum~~Jndlngs. • Ungual branches: somatosensory flbers ind gustitDry flbers for the posterior third of the tDngue.
Postganglionic parasytn· pathetlcflbefs (run a short d1stance w1lll IN! JiUriCU~por~~ln~}
lnftrlar
g~ngllon
D lr;mcheufthe glllssoph;lrynge;~l nerw lr1 tfletymp;mlc catty Left ant2rolmral lltew. The tympanic nerw, which passes through the tympanic canaliruiLII into the tympanic cavity, is the first branch of the glonopharynge;~l nerw. It COfltilns vlKeral efferer~t (pmynap1k para·
symp;ltbetlc) flbers for the otic gangllor~;md somatic alferer~t fibers for the tympanic caVIty and pl\aryngotympanlc (Eustachian) I:IJbe. It Joins with sympathetic fibers from the carotid plexus (via the carotiCDtym· panic nerve) tD form the tympanic plexus. The parasymp;ltbetlc fibers tr.wd asthe lesser petrDsal nuve tD the otic ganglion (see p.99), which pi'OIIfdes parasympathetic Innervation tD the parotid gland.
E VI tee I'll cffen:nt (plruympriu:tk) flberuf the iJossopharyngeal nerw The presynaptic par<~sympa!hetlc flbers from !he Inferior sallvatory nucleus leaw the medulla oblongata with the glossopharyngeal nerve and branch off as tile tympank nerw lmmedlmly afta'emerglng from the bue of the skull. The tympanic nerve dlllldes within the tympanic cll\llty tD form the tympar11c plexus (seeA,p.144),1Mllch Is Joined by po.stsynaptic sympathetic fibers from the plexus on the middle meningeal artery (not shown). The tympanic plexus giftS rise tD tile lesser petrosal nerw. which leiYeS the petrDus bone thrDCJgh the hiatus of the canal for the lesser petrosal nerw and ent2rs the middle cranial fossa. Coursing beneath the dura, it passes through the foramen laarum ID the otic gar~gllon. Its fibers enter the aurlaJiotempor;~l nerve, pau tD the facial nerve, and Its autonomic fibers are dlstr1bull!d to the parotkl glaoo via facial nerw branches.
15
Head - - ... CnmltJI Nerw.s
4.11
Cranial Nerves: Vagus (CN X)
The vagus ntn~e CDI1talm gmeq!IIMI Jlledal V~sctr.r effeRntftbm .,well.s vtsarallllliennt and SOIMik llltlnntftbers. It his the most t:lllll!nSive clistrbD>n of.. the a.lill (vagus • "lllglbond") and CDIISists ci aanbo I, .,..,..., tt-.clc, ...:lllbdomlnal p«ts. This unit dells ""'lnly with tlw vag.. nerw In tlw hud lind n~~ek (Its thoracic •nd 11bdomln~~l ports lire de:Krf~ In the volume on the Neck ;md lntemill Org~ns).
DarMI ¥1!1111 nudeus
SIN af..-gene.: The VIllUS nei"VIt tmc
Nuder •d dlllrllulllln, gongllo:
• 5P«kJJIIISCMJ/«ffmnt~): ~tillers from the
)'gular foramen
Splnolnudeus ofb1gfmlnllnfiW Dai'Mivag;~l
N.=.u~~~tho! nuclous a~por1Drport
Nudtw of the IO~'Yli'ICt. l~orport
=~ Nudeus •mblguus b
Olivo!
A Nuclei of the wguuwrw. ~ Medulli oblongabl, anmior view showing the site of emergence of the vagus nerve. It CnJss..sectlon through the medulla oblongata at the level of the superior olive. N'* the various nudei af the vagus nerve and their functions.
The RUCkus crmbiguus contains the
JOmOPc ~t (branchiogenic) fibers for the superior and Inferior laryngeal nerves. It hasa somatotopic organlzlltlon,l.e., the neurons for the wpmor laryngeal neiVI! are above, and thase far the itt[MDr laryngeal nerve are below. The dot:sal nucleus of the vagus nnw Is located on the floor of the rhomboid fossa and mnbllns presynaptic, par.aym pll:hftlc vlsanl efferent neurons. The sonnauc ~nt fibers whose pseudounlpobr g1ngllon cells are locat2d in the superior Qugular) ganglion of the vagus nervi! urminate in the spinal RUCkus of tift! ~o/ nerve. They use the vagus neM! only as a means of cunveyutce. Tlle central processes of the pseudounlpolar g;mgllon ails from the Inferior (nodose) ganglion ilre gustatory fibers and visceral afferent ftbers. They mrmlnate In the nucleus of the sollt1Hy
Inlet.
86
nudeus amblguus supply tiM following musdes: - Pha'Yngeal muscles (phlryngul branch, Joins wtth gfosso. phlryngealnerw to fonn tiM ph1ryngul plibUS) 1nd muscles of the soft palate (lem:or wll peLitlnl, mulde af IMIIa). - Alll•ry"!!""l muscles: TIM superior I•'Y,...I nerw supplies the a10lthyrold. while the lnferfor llrynget~l nerw supplies the other laryngal muscles (the orfgln af lhe llblrs Is described on p.ll). • GI!IMI'IIIvlsarollfrttwlt~- Dg): PinaympatheUc pn!SyNiptic ~from the do~l¥11gll nudeus MrVe syNJlM in pn!'letmbral or lnlnlmural ganglia wllh pasbynapUc fibers Ill supply srmath muscles •nd glands af: - thon~dc vlsall and - abdominal vtsan as far • the 11ft calrc ftealre (cannon-Mhm point)• • Somatic l1{frnnl: Central pniODeS ci pseudaunlpobr gongllon aoh ~Dated In tiM .suporior(;>JuiDIJ ~ cithewgus tl!rmNte In the .pn. I roudeul d the trtgemlnll rww. Tlw ~~~fila's orl!lln*trom: - the 41nln the ~cnnlll ross. (menlngul branch. see Df). - • small- at the skin ofU. Dlt) and Ullmll .....,.,.,.,.. (..rra.llor br..dt,- Dq. n....ncu~ar ~Hand!
pinna<-
Is the onlyc~ branch dthewgus rwrw.
• 5P«kJJIIISCMJI.,..,_ C.nlnll p.-.s at pse.udounlpoi;lr ga ngllon cells from the lmrlor nodose g1ngllon tennlnll:e In the su perlor port of the ru:llvs of the solltlry tract. Their peripher~l processes supply tiM WtJt buds on lhe epiglottis (see Dd). • Genmol viJizrDI o/femrt: The perlkary• mtt- .tfarw1ts •re •loa located In the Inferior ganglion. Their Clelllnl p~DCZ~Sesllnnln•.. In the Inferior part at the nudeus olthe $01brytflct. Their peripheral prooesses supply the following oreas: - Mucasa at the lawer pharyl'lllat Its junction wllh the esophagus (see De) - la'Yngeal mumu •bow (superfor !.ryngul nerve) •nd beiCM (lmrlor l•ryngeal nerw) lh•IJiotdc 1perture Dll) - ~ure reaptorJ In the aorUc an:h (see De) - Chemoreoep4Jors In the parHortlc body<- De) - lhoradcand abclomrnalvtsc.ra <-Dol
<-
Dewlopo•••LIIIy, the VIgus nerw Is tlw n Jlxth bronchial •rch.
mlhe fourth and
Astructure of ~n~jor dnlal lmportllnce Is the I'I!'CUmllf laiJngeal - . whkh supplies vrsaromoUir Innervation to lhe only muscle that 1bducb the vaal canis, tiM ~rlorcrl.,..rytenalcl. Undmral destrucUon of this -leads to hoilrwness. 1nd bllilten~l destruc:JJon leads til respiratory dlsnss (~).
HeGd - - 4. Ctvniaf Nerws
- - - l'haryng""l brandies - - SUps1or
Lal")''l!!""'........e
11112malbr>ndl
!-:'---:7- - Leftlrhrior
ltlghtlnferlor -~~e--;·,;,.,
loryngoolnorw
loryng..lnorw
01~1d ---~::;#-J;~~----
ExtJemalbrinch
muscle
Subdnlon or111ry Bntehlo- ----+-n--
b
aphollc trunk
C Br1nches of the Wlgus nerve (CN X) ~ tht neck il The vagus nerve gives off four sets of branches In the neck: philryngeal br~nches, the superior laryngea I nerve. the rewrrent Laryngeal nerve, and th~ ~cal cardiac branches. The Inferior laryngeal nerve h the b!rmlnal brinch of th~ reament laryngeal nel"4. It winds around the subcLavian artery on the right side and arvund th~ aortic ilrch on th~ left side. On that side It Is In dose rebUonshlp tD the left: main bronchus. A lesion of the Inferior laryngeel nerve (e.g., due to pressure from a nodal metastasis of bronchlill Cilrclnomil or from an aortic aneury5m) may lead to hoarseness (lntr1nslelaryngeal muscles). The Inferior larynge•l nerw passes dose to the posterolmrill aspect of the thyroid ~nd. IT'Iilldng It suscepUble tD Injury during thyroid optBtlons. For this r.Yson, ,;m otolaryngologi$l should asse:A the function of the laryngeol muscles prlor1o thyrvld surgay. b Muscle suppOed 1Pf the superior Ia ryngeal nerw.
~~---_.~~--~
cordiac brlll
•
c
e D
•
Vlsce.n l1nd -rydlltrtllutlon of the WIUSII-{CN X)
87
Hettd - - 4. CIVInhJI N«ws
4.12
Cranial Nerves: Accessory (CN XI) and Hypoglossal (CN XII)
C Onnfi!W ofthucr:lll!lliOI'JMI'Ye (CN XI)
TM accessOI'f nerw Is considered by some authors to be an lndfpfndmt p.art oftt. wgul nerw (CN X). It conblins both visceral and somlllic efferent flbe~. and has oM cranial and one spinal root. Sites el em....-: hsplnal roat emerges from the spinal cord, passes supertcwty, •nd en~ tt. skull through the (onrmen mOllllum.. where It tolns With the cranial root
from the medulla oblongata. Both roots then 1etw the skull lllgether through the jugular{otomen. While still within the jugularforamen, fibers from the cranial root Pllll to the wgul nerw (lntlernal branch). TM spinal porUon descends to the nuchal region as the l!ldlernal branch ofthe accessory-.
A Nudaus W
CIDUFM ofthl _.,1111"11'11
Posterlorvlewoftfte br.llnstem (wl!hthe ce~ bellum l'l!moved). Fclr didactic l'l!.asons, the
muKies are displayed from the right side (seeC for further details).
\
~;.~ b
B LetTon of tfle 1cauory nl!f'ft (onthe~slde) <11
Posterior ¥few. Piralysls of tile tripezlus muscle causes drooping of !he shoulder on tfte.aft'ectl!d sllie..
88
b Right inte!'Oiatefal view. Wltft p.aralysls of
tile sb!rnocleidomastoid mus~ it is difli· aJit for the patient to turn tile head to tile opposlll! side igilnsta resistance.
NudeT and dlllrllutlotl: • Ctonial tOOC: The special visceral effefent flbe~ of the accessory nerve that arise from the caudal part of the nucleus amblguus JOin tt. Vli!IUS nen.oe and are distributed with the recunent Jaryngeel neMt. They lnneMtlt all of the laryngeal muscles eca!pt the criCDthyroid. • Splnol tOOC: The spinal nudeus of the accessOfY nerw fonns a nanvw a~lumn of celllln tt. anUrlor hom of the spinal cord at the level of C2-CS/6. After emerging from the spinal cold, ItS somalfc efferent fibe~ form the -mal branch of the •a:zssOIY nerw, which supplies tt. trape21us and stemodeldornastold muscles. Elfwdsof•-ry-lnJury A undateral lesion results In the follOWing cletldts: • TAipeliuJ ~ chantcte.U.d by drooping of the should.-and difficulty raising the ann alxM the horlmntal (the t111perlus supports the ser111tus anllef1or In eleVlltlng tt.ann past 90'). The part of the accessOfY nem thillt supplies Ute traperius is wlnentble during operations In the neck (e.g., lymph node biopsies). Beause the lower portions of the muscle ~~also Innervated by segments 0 and C4/S, an InJury oftheaccessOIY neMt Will not mult In 011mplete trapezius p.aralysls• • ~IISIDid prwlysis. chantell!lbed by lllrUCDIIIs (wry neck. I.e., dl~ cultytumlng the head Ill the opposite side). Beause thll mulde Is supplied wuslwly bytt.accessOfY neMt, an InJury to that neNe causes ftacdd paraly· sis. W'lth billtentl lesions. it is difficult for tt. pellent to hold the head In an uprlght position.
HeGd - - 4. Ctvnial Nerws
E Dwnll-ofthe hypoglaulnerw (CNXII)
Hypog.....ltr1gane ~n rhomboid fana)
The t.,pogloswl-11 ' Pl"lr SOfNit1c: elftrtnt tNt supples the IIIIISCih-
Hypoglo~
MMI!
Ollft
Nud...atthe
hypoglossalnenoe
a
lheh)opo-
\
9...... .......
I
Foramen
In the floor cfdle rhom bold bsl. Its solllll:lc tft'erentftbers emerge from 111e medulla oblol'lglti,IHving the c:ranilll Col'olltythi'OIIgh tile hypoglossalcanalillnd deKitndlngl.t.1111ott.vagus- The
..
gkllsalnenoe
Cross-section through the medulli oblo!lgm at the level of 111e ollva. This section passe5 through the nucleus of the hypl)glossal nenoe. It nn be seen that the nucleus lies just beneath the mom bold foss~ and raises the floor of the fossa to furm the hypog los~l tr1gone. Because Ndl nucleus
lllooct..MIIsb_,_,......The nudtus of the hypaglaaolneJWis1aaled
magnum
Clnalof~
D NudeTofthe~loeMinenoe il
lllredtt.~.
Nudruul"
Cl splnaiMMI!
~lossal nerw enters the ~of the IDnguubcowthe 1¥1!d bDne onddlll:rlbuta Its fibers there.
i$ close to the midline, it i$ mmmon for more extensive leJions to Involve the nuclei on both sides, producing the dlnlc.al manlfatations of a bilaWr.~l nude<~r lesion. b Anterior view. The neurons contained In this nuciNr mlu mn COITI!SpOild to the alpha motur neurons of the spinal cord.
D_.lltlon: The hypoglossal nerve sup-
pfles 1lllnt~nslc 1nd ut~nslc musdes of the IDngw (acept for the po imlgiDUus, CN X). It can be mnsldeM 1 "zlorath" wntral root rillherth1n 1 true cnmlll- Thever.tral fibers of C1 and a ti'IWII with the hypl)glosul ...,.. but l - I t again .Jfter a short
dbtanoe to form the superior~ ofthe (deep) InN! QU\IIcalls.
l'nlanlr31
of..,_.._,_,.,._,ury:
sr.cb • Centr1l hypoglossal p11r111ysis (supnonuclur): lh•tangue ct.vlau WRI'f from the side of th• lesion. • Nuc:INr or perll)hlral pual~ls: The
Loft and right
;}''· r \1
gmiDglouiB mLISCies
~ dwlltaIDwlnltt.ilfKtl!d side due to 1 P4 epo~ld!nl e d nuculir ldlon on the healthy side.
c
">-- - - CGrtlmbulbor
stylogi1151U5
fiben
musde
F Dlltrtbutlon oldie ~lolull'll!rw Cenlro~land peripheral course. b Function ofthe genioglossus musde. c Deov!Mlon of the tongue !:owlrd the paralyad side. The nucleu~ of the hypoglossal nerw is innerwted (upper motor neurons) ~ cortic:;ll neurons from 111e contralateral side. With a unlllltl!ral nltdfor or pertpherol lesion of the hypoglossal nerve, die tongue devl.ib!s tDwird die side of the lesiOn when protruded because of die reliUve dominance of the healthy ga'lloglossus muscle (c). When both nudel in! Injured, the tongue cannot be prGtruded (flaccid paralysis). •
....... MMI!
.......
• 89
Hettd - - 4. CIVInhJI N«ws
4.13
Neurovascular Pathways through the Base of the Skull. Synopsis
A SltK wfwre nerws ;md - " ' p;111 through the skull INA IJ!ft half of dra!Mng: fntem.-al'lltew of the base of the skull. Right half of drawing: exlli!malvlew of!he billie of the skull. Because the opening ln1D tfle crilnium is not identical to the site of emergena on tfle extemill
90
-
.............
1rtay
C.O.....GIIYI
Condylu antaarylll!ln
.-aspe<:t of tfte base of the skull for some neurw.~sa~lar structures. the site of entry Into the cr.-anulm Is shown on the left side .-and the site of erne11ence Is shown on !he right side.
Head - - 4. Crankll Nerves
Opening
'Tnnsmltted structu,..
lntemll view,INse of the skull Anterior c:ranllol foua
B Principal sites where neurovascular structures pass through the skull bilse Note: The eltternal opening of the foramen rotundum Is located In the pterygopalatine fossa, which is located deep on the lateral surface of the base of the skull and is not visible here.
This chapter describes the topogr.ilphlcal aBatomy of the anterior .ilnd l~teral aspemoftfle he;! d. It is ii$$Umed th.irttfle reilder is<~lre<~dyf.lmili~r with the skeletal, muscular, ind neui'OYilscular anatomy lllll!tr.lted In preYious chapters. The most dlnlcally Important regions around the eyes, no.s.e,and ears aredescribed in separatechapben.ln tflischap!zrthe
various reg!orts of !he t'ac!!. head. .ilnd neck are dlspl~ on the ewnnum"-d p.ages (left-band ~de), whne the odd·num"-d p.ages (righthind side) p!'O'IIIde Information on functional groups of specific iniltDmlcal structures .ilnd their dlnlcallmportance.
A SupHfldllnenresl!nd-boftflel!ntl:ftorhdlln:glon The sklflind f;m:ytlssue have be1!n removed to demofiStrate tfle superficial muscular layer, the muscles official expression. This laya'has been p.arlially temCM!d on tfle left side of the f.ace tD display underlying portions of tfle musdes of mastfeidon. The muscles of Cl!Pression receive their motor lnr~erv.rtlon from tile {odc!l netW.. which emerges laterilly fi'om tile parotid gland. The face receives Its sensory lnnerv.ltlon fi'om
92
Ment.l n~
the trigemlnalllC!rl'e. whose tfn-ee terminal branchn are shown here (see E), Brinches from !he third dMslon of the trigeminal nerve iddltlonally supply motor Innervation to the muscles of mastication. The face receives most of its blood supply fi'om the mrmo/ mmtid ar!l!l)t Only small aren around tile medial and lateral cantil! of tile eyes 01nd In the forehead are supplied by the Jnll!ma/ CGroffd or!l!ly(seeB).
HNd - - 5. TopogmphlcGI.Ano1Dmy
Dorsai~~~S;~Ial'll!ry
- - -+ - -.,;.,'-7----
"("-~--+----
Xilr...::;;;;,...,....___:~r-----
uural palpebral
Sup11101111t
lll'ti!I!H
./"\ -- - - Superfidlll tl!mponl1111!ry
r- - - - Dttunal
ca ralld .wtl!ly
8 DlstoriiU'Ikm of the atam;ll Glrolfd art.ery (red) and tntl!mal urottd illltll!ry
{brwm}lntfleflce Hemodyn~mically signific;~nt
anartomoses may deYelop betwHn ttle$e two ~rtaial tml· tortes. Even il ~rtred reduction of flow In Ute Internal carotid al'tl!ry by ~!herosclerosls may
not le.ild to cerebral Ischemia, as long as there Is .ildequate compensatory flow tftrough the superficial tl!mpor.ill artery. If this is the case, tftm ligation oftfte superflcial tempor~l artery Is conttalndlt."!ted (tile artery might otherwise be ligated, for example,. In a biopsy to confirm Ute diagnosis of temporal arteritis;~ p. 59).
C Triilnguludlngerzone lndlefiiC8 This 1011e Is mart.ed by !he pnesen1:2 of venous connections from Ute face to the dural venous sinuses. Bec:i!use the veins in tftis region
Superlat
ophltlalmlcveln
Ophthalmic artl!ry AnQularartl!ry - -df <~ndveln
Sltefor - --t\ • galtlg ltle angularwfn
____.- Superlat ~ petrosalslnus
r----s...,aarflltol MrYe
------ lnhrlor --petrosal slrw
(br.aru:naf~V1 )
..---;~----.,...--- Maldl;uy~h$
...,...._...:......_ Sigmoid
s'tlus
'+-- - - - lnfrlarbltal I'I8W (blllndlof~V:z)
'----'------==- - lntemlll ]ugularwln
E aJntcallytmportilnt sftes of etnel'llei'ICII!
aftflethn!e trtgeml'NII nerve brandies
D Clfnluly lrnpolt.ilnt vucular ftlltloMhlps In tfle flce Nok the connections between the extl!ricw of
the face and Ute dural slnus;es. If .il purulent Inflammation develops In Ute "danger zone• (see C), Ute .ilngularvefn c;~n be
ligated at a standard site to prewnt Ute transmtsslol'l of lnfectfo~K organisms to the c.avemoussinus.
The trigeminal nerve (OIV) is the major ~ ~tic sensory nerve of Ute heild. The dtagram shows Ute stll!s of eme!'gen1:2 oflts lhnee lil~e sensory br.ill'lChes: • br~nchofCNV1 : supraorbitlll neM! (supraorbltlll foramen) • branchofCNV2: lnfraorblt.ll nerve (tnfraorbltlll for.ilmm) • branchofCNV3: mental nerve (mentlll foramen): see alsop. n.
A SupHfldllveaekmdnervaofthehud l.clt lall!fal view. All the irteries visible In Utls dlagrilm irlse from Ute mrmol Ctl1'0tld ortl!ry, which Is too deep to be Wible In this superfldal dissection. The lateral he.'!d region is dr~ined bytheertf1f!Gijugulor!il!in.. The facial vein. however. drilns Into the deepa-lnternaljugularveln (not shDWn here). The (adal rtfiYf h;ss divided ln Ute parotid gland to form Ute p.arotfd plexus. whose br;mches leave Ute p.;~rotld glarld at ItS anterior border and are distJibuted to Ute f~tial muscle$ (see C). This la!J!r~l
94
Ext!!mal
fugularwln
head region also recdves sensory lnnuvatlon from brinches of the frl· gemlna/ nt!fVt {see D). while Ute portion of the occlput visible lt1 the drawing Is supplied by the gi'MfT and lessf!r OCCQlrtDI tl1!M!S. Unlike the trigeminal nerve. thecaipital nerves origina!J!from thespinal nervescf the cuvlc
HNd - - 5. TopogmphlcGI.Ano1Dmy
SUperfiCial tlemporal <111:2fy,l'rontal bra nell
Mlddleb!m-
pot;llal'tl!ry
Superior 101b1011<111:21'y
lrhr'lor -----. lolbiOII<111:21'y
lnfetlar /
.alwolaral'tl!ry. mental bra nell
::::z:'
Mallinal - ----,-=,..-·71
I
./
Submemala~
mandlbulilr bnlndl
-11- - - - Motorbrandles ID rtylohyald and d\Q&rlrlc {pos!l!rlor belly}
Facial <111:21y
8 Superllctal br.lndles oftfle l!ll.tl!m;ll Glrotld ilrt.l!fy 1St laterill VIew. Tills dlagr.ilm shows the .ilrterfes lfllsolatlon to demonstrate their branches .ilfld their relationships to one another (compare with A; seep. 54 for det.illls).
C FiKhiMaw(CNVJI) Left lateral lllew. The mwdes of f.ildal expression receiVe all of their motor innervation from the seventh cranial nerve (seep. 79).
Left l;ateral view. In the region shown he<1!, the he;~d derives its somatic sensory supply from three large branches of the trigeminal nerve (supriloltlltill nenoe. tnfrilorbltill nerve, and mentoll nerve). The diagram II· lwtrates thelrcnurse tn the skull ilnd their 5ltes of emergence In the .iln· tetiorf.lciall'l!gion (see the .ilnberiorviewon p. 92). The trigeminal nerve Is partly a ml1!.ed nerve because motorflbers lr.IVel with the marldlbular nerve(= third dMslon of the trigeminal r~erve) to supply the muscles of mastication.
E Nef'ft tellftorles of the Iatini head and n«k Left later.ll view. Noa: The laterill head ;and neck region receives Its sensory supply from
aanlal nerve (trtgemiNI nerve ;md Its brilnches}, ;md from the dors.al rilml {greattr ocdpltill ne!'Ve) and ventrill r.ilml (lesser occipital nerve, great aurirular nerve, transwrse cervical nerve) of spinal netVI!S. The C1 spiN I nerve has a ventral root, contllnlng mawr flbers, but r10 dors.al root: Ittherefore provides no SEnsorylnnerviltlon to the sklr1 (I.e .• It hillS no demnatome). OM
95
Head, Lateral View: Middle and Deep Layers
5.3
S\CH111rCKhlearneM,
supnartltal nerw
------:lf/#;~lt!o..
(br.~nclld~V1 )
FlldalneM. bucal bnnc:he Menlll~ ----&~.1/l
{bnnc:hof
CNV:s}
fadall'll!rW, marghal mancf· bularbranch
A VKselnnd ncrvcufthe lntennedlllc I~ l.clt laterill view. The parotid gland hils be\!11 reiTIOYCd to demonstrate the struc:tllre of the lntrip.uotld plexus of the facial nerve.. Note c.ertain nervu hall!! been di!SCribed in pn!Yiaur. units. The ftlns have been removed for dartty.
96
lntr;parotld plexus
HNd - - 5. TopogmphlcGI.Ano1Dmy
Allrtrulot!em·
Po.stl!!for sl.pelfor aM!alar
por.aln~
Superfldilltem·
pollii..Ury IJI!Jer.al ~dmusde
lnfraorblt
Middle menlr>geal artel)'
BucalnerYe
MD!IIaly
Bucxfn.atllt
mustle LllgualneM
~riot ;~M!alarn~
Inferior Mlooedar
8 Vencfnnd m:m:ufthedecp III)'Cr l.clt later.~ I view. The masseter musde and zygomatic arch have been dMded to gain .ilccess to the deep strucllJres. Also, the r.ilmwo of the marldible has been opened to demonstrate the neunw.asrular struc· tures th.iltti';M!rse It The veins have been completely removed.
Ulteral VIew. A separate unit Is devoted to the Infratemporal fossa because of the m~ny roucwres th;at it contains. The zyg~matit ~rch and !he anterior half of the mandibular ramus hive bem re!MVed In this dlssectlor1 to gain aa:ess to the Infratemporal foS;Sa. The mandlbu·
Jar canal has been opened, andUie Inferior alveolar arll!ry and nerve can be seen ent:trlng the canal {the accompanying vefn h~ been removec:l}. The m;WII~ry artery dividn into it$ tenninal branches dHP within the lnfratempor;ll fos.sa (see 8).
8 lett1'nlratil!mponl fol11, deep layer l..ater.ll view. This diln!rs frvm the previous dissection in th;at both he;td$ of the lateral pterygoid musde have been partlally removed, so that only their s!IJmps are llfslble. The branches of the maxlllary artery and mandlbcJiar dMslor1 tafl be Identified. Bytareful dissection, It Is possible
98
Me;lial pterygoid muscle Faclllln~
lrhrtor
to define Ule site where the aurfCIJiotemporlll nerve (branch of the mandibular division} splits around the middle meninge~l ~rtl!ry b~ fore entering the middle crar~lal fossa through the foramen splnosum {seep. 59).
lind -
5. Topographlml Anafumy
Mllllary dlvlllon Ophlhllmlc d!wtslan Mandlbu!.rdMslan None d IB!sor
tymponl tadai i'IOM! -----,~·
"bclal unal Tensortympani mUKit
C Left atlc pn1llon and Its roob loatH deep In tile lnrr.tlemponl-.,
Medii!I Ylew. The small, flit otic ganglion Is located medial tDthe mindlbulilr nerwjust lr.-
ferlor to the fora men oville. The puiiSym~etic: fibers for the parotid gl;lnd are relayed In the ganglion (seep. 85).
c
lnflftcr
UngLIII nt
lnflfkr
Unguol none
alveolarrwve
Milllllary dllottlon Mlndlbullr dolslan
•
Mo!nlng• l b111nch
alveolar nerw
Deep12mpo1111
""""" llur.alnerw _
Mecllillp1J!I')'ll01d
•
-~------:;;
___...;.;:! =0( --J
7
lnfttlor
Unguol none
1lveolarnerw
nerw Alrl::Uo· 12mpo11111'10M!
UngUIIro.rw
Bucdrwtar mlllde MalHII!rlftlsde D llnnches afthe mlndllulilr division rn the lnl'nltllrnporel ,_.
Left imAI view. The medlirl pterygoid muscle can be ldentlfled deep within lfle foSSil. The third divil;ion of the lligemi"'l nerw paSJeS
Medlill pllr}ogold
mlllde through the forilmen ovate from lfle middle cranial fGssa to enter the infratempo~l fossa. Traveling with It are mumr fibers (matDr root) lhilt supply the muscles « mastication (only a few of the liben are iiiU51rated here).
E YirtrlntJ ot tile left mlllllll.-y .-ll!ry
Lateral view. The course of the m;ndllary artery Is subject to consld8<1ble varliltlon. The most common variants are listed below. a Runs literal to the literal ptl!rygold musde (common). • Runs mediiIto the liter
d Runs between the branches of the inferior alveolir nerve. e Runs medial 1D the trunk of the lnfel1or ilveol.a r nerve.
A CourM ofthnrtarfK In the left pt81Jt0p;llatfnefosM Urteral ~ew. The lnfr.rtemporill fosSil (see previous unit. p. 98) Is continuous Mth the pterygopalalfnefosSil shown here, with no de.-.r line of dem~rcation betwl!en them. The anrtomic~l bound~rie.J af the pterygopala11ne fosSil are listed In B. The pterygopalatine fossa Is.-. aossroad for ne\lrovascular structures traveling between the middle cranial fossa, orbit. nas.al c;Mty. ilnd or.al CiiVlty (see !he pasSilgeways In E). lle
c u.,.er lr.lndles of tile m.ullary ill'teJY The maxlllary artery consists of a mandibular part. pterygoid part. .and pb!rygopalatine part. Because the vessels of the mandibular part lie ouWdetltearea aftltedlssect!on. they a~ not listed Jntltet.1ble below (seep. 58). lnnch Motldll>cdor port seep. 58 l'tf(ygoSd ptl1t: • Masseteric amry • Deep temporal arteries
• Hand palate • Soft palate. palatine ton~ll. pharyngeal w.all • l..at.eral w.all of nas.al cavity, d'toanae • Nawl sepCIJm
HNd - - 5. TopogmphlcGI.Ano1Dmy
lnhorbitlllllln'e
Orbit<~~ br.uldles Gingllonk br.uldles
Ma:dlaryneM ~~~orbltlll--~------~==~----~
Nasapalallne ne~W,
IMt.n!
medial .and laller.ll superior pa.stleflot nasal bt.anches
~------ Plo!rygopalall'le ganglion
==i------ Nerwof pterygllid anal
Nlaopelltfnenl!l"fl', - - - - - - - -_..,.
postl!dcrlnfwlor n&'l.llbrardles Gl'llilte-
palitlne.-
Gruta-l)etrO/I;IInerw
----:----=-""'"
D COurse of tile nerves In die left p1ief'ygo~U~'-tlne ro.. Latl!r.ll view. The m.MIIary division, tile second dtvlslon of CNV, passes from the middle cr;mlal fossa through the forilmen ro!:IJndum Into the ptt!rygop.alatiAe fossa. Oosely related to the maxillary ni!M! is the para· symp.athetk pterygopalatine !Jilngllon, In whkh preganglionic flbers synapse with g<~ngllon cells that. In tum. lnnew.rte the lacrimal glands and the small palatal and nasal glands. The pterygopalalfnegangllon re-
«ives ~ pre~ptic fiber$ fram the gre~~ter petrosal nerve. This nervt' Is the parasympathetic root af the neMIS lntemnedlus branch af the f.t. clal nerve. The sympathetic flbers af the deep pettoSill nerve (sympathetic root), lila! the Sl!ns«yfibersofthe maxillary nerve (sensory root),
piiSS through tile g<~ngllon without syn;~pslng.
E Pill!ls.Jgew.ll to the p11ef'ygop;~I;!Une l'o:!ls.J and trart!lmlttl!d neui'OIIIilscular structures
.........,.
Comes from."
F0111men ro!:IJndum
Middle cr1nlal fos:sa
• Maldllarynerve(CNV:z)
Pterygoid canal
Base ofthe skull
• Nerve of pterygoid anal (grater and deep petros.~! ntr~~eS} • Artery of pterygoid an<~l with .acccmpanylngvelns
An'terlorvlew. The upper arid lowerllpsme«attheangleofthemouth. The oral ftssure opens llltO the orill alllty. Changes In the lips noted 011 visual inspecticm may yield imporbnt diagncsticdues: Blue lips (cyanosis) suggest a disease of the heart.lu~~g. or both. while deep nasolabial creases may reflect chronic dlseises of the digestive trict.
moulh
8 Or~lavlty Anterior view. The dern:al arches wtth the alveolar proce!.Ses of the maxllla ;md mandible subdivide the oral cavity Into sever.ill p.irts (see also C): • Ot.ill vestibule: the p.itt of the cral cavity bounded on cne side by the tftth and orlthe other side by the lrps orchecb. • Oral c.ntty proper: the cavity of !he moulh In the strict sense (within the dental arches. bounded posteriorly by !he p.ilatoglossal itch). • Fauces: the throat (boundary with the pharynx: palatopharyngeal arch).
Hard
p.Mitl!
P.lllltogloml
SCft
p.Mitl!
P.llatopharyn-
:-.~~u..:.---I.Mlla
gealarch
1-- - P.llat'he
Faudal lslhmus
ton Ill
The fauces communicate with the ph;lrynx through the faooal isth· mus. The oral avlty Is lined with llOillceAtlnlzed, stratified squamous epithelium !hat Is moistened by seaetfons from the S.illllr.lry glands (seep. 113). Squamccacell carcloomas ofthe oral alllty .are particularly common in smo~ and heJvy drin~.
C 01'11anlziltlon ;md bourldarfes of tile Ol'ill CiiVIty MldSilgltt.ll sectfo11,left tmral view. The m~&Sdes of the oral floor .ilnd the adjacent tangue together constitube the inferior boundary of the oral c;wltyproper. The roofoftheoral avlty Is formed by the hard palate 111 Its anterior two-thirds and by the soft palate (velum) In Its posterior third (seeF). The uvula hangs &om the soft palate between the or.ill
102
plt;lryn:x
o,. phlryn:x
I.Oiryngoplt;lryn:x
cavity and phirynx. The tceraunlzed s1ratlf!ed squamous epithelium of the skin blends wtth the nonki!r.atln!Ud stratified squamous epithelium of the e~ral avity at the vermilion border e~f the lip. The or;I cavity i' located below!he nasal C3111ty and antertorto the pharynx. The mldport'kln of !he pharynx. called !he oropharynx. Is the area In ~Mllch !he alrw;ry and foodway lntenect (b).
HHd -
Postl!lfor ------.=~~~IY
"·~
_,...____.
~"•1*:0.....,*--~,.,..=.---- Nasopala1tl~
Sl!ptallnndlu
n~
· - ----~;;t:;~~~~
foramen
)'-l~+:...,;,----ll!.--- Mtd'an palaUne
sutune Cnsrtl!rp;~latlne
!laW
CI"Ntl!r p;~latl~
Le~rpallltlne
foramen LA!SUI'PIIItfne foramen
Pllerwold
-....;:o~'"?'!!ii
hl~n~~lus
~,__
lnfr.aorbltal.antl!rlct superlct .alveolar branchK, michie superior Ml,oeol~ r bra nell
_
__;,.,.~~-- NasopalaUn~
ner\'e
D Neui'GRIClll;ir structures of the hard pilite Inferior 1/iew. The arteriH and nerves af the hard p;rlm (skeletal anat»my Is shown on p. 28) pass downw;rrd through the lncls'llle foramen and the grea~rand ies,ser p.alatiAef~ ramlna Into the oral cavity. The nerves are terminal br;rndtes af the trfgemln;rl ne~Ve's m;rxlllary dMslon (o.J V1), and the arteries artse from the territory of the maxillary artery (Aeither are shown here)
E
Sensoryrnnervltlonofthep~lml ITIIICIIA, upper lip. dleetrs. and sfnghr.a
lnfenor VIew. Notr: that the region shown in the drawing
recdves sauory lnnerv.rtfon from different branches oftile trfgemln;rl nerve (bucul nerve from the mandibular diVIsion (CN V3, all other bran the$ from the maxillary division, CN V1).
F Musclu ofthuoft p.alltlt lnfenorlltew.Tilesoftpalatefonnstheposterlor boundary of the oral c.Mty, separating it fram the oropharyruc. The musdes are attached ;rt the midline to the palatiAe ;rponeurosls. which forms the connective Ussue foundation af the soft palatJ!. The tzn-veli palatini,levatorlll!!li palillinl. and musaJius uvulae can be ldentl6ed In this dissection. While the tensor veil palall:nl tightens the soft palate, simultaneously opening the inlet to the pharyngotymp;rnic (auditory) tube (seep. 145), tfte levator veil palatinl raises tile soft palate to a hol1mntal position. Bolh of these musdes, but not the musaJius uvul~e. also contribw! structurally to the lateral pharyngeal wall.
103
6. Orvl Cavfty
Hftnl -
6.2
Tongue: Muscles and Mucosa A SUrhu ilnlltomy of the R~t~Uill rnUCCBil
Ungllll tonsil
Fo~amen
awm Polilllne
ton•ll
DoiJLm
Body of tong..
' - - - - - ApOKof
Supericlrview. While the motor prope.rtla of the tGfi!IUt! Me func~ lly Important during mutlatlon. swallowing. and spe~klng.lts eqtlllly Important sensory functlalls InClude tJstll! and fine bctlle dlsalmlmtlon. The wngue b endowed with a very p-"ul muSCl.llilr body (seeQI). The upper surfKe (dorsum) of the wngue Is covwed II¥ il highly Sf»' cialiad mucosal coat and conslsb, fioam fioant to back. of an api!X (tip), body. 11nd root. The V-shaped funvw on the dor.ul surface (the sukus termlnalls) further divides the tongue into an ~~~rior (oral, presulaO part and 1 postErior (philryngeal. postsulal) port. The anterior port comprises the anterior two-thirds of the tongue, and the posterior part campri!ellhe postErior third. N: the tip of lfle "V" Is the foramen czc:um (veJt!ge of embryologlal migration of the thyroid gland}. This subdivision Is a ~ suIt of embryvloginl development and explains why each part has a different nerve supply (see p.107). The mucosa of the anterior part Is composed of numerous papillae (see 1), and the connectlw! tls:sue betw.:en the mucos.al surface and muKU Iatune contains many small saliwry glands. The physician should be fa mlllilr with them, iiS they may give 1tse to tumors (usually malignant). The mw buds are bordm by serous gl11nds (.see lb-e) thilt ire known also as wn Elmerg/ond$; they produce a watery secretion that keeps the tastll! buds dean.
8 Thc,.pll•cvfh""'guc iii Sectlonil block dlagl'lm of the llngt~~l piplllae. b~Types of piplllae. The papillae ane dMded Into four morphologlally distinct types: b vallate papillae: enclrded II¥a wall and cantllnlng abund.;;mt bstll! buds.
104
e
c f\lngiform papillar. mushroam1"'pcd, located at the sides of the tongue (they hi~Ye mec"'nlal receptors, thermal receptors. ;md ustll!buds). d Filiform papillae: thread-shaped papiUae lf1at are seruit~ tD tactile stimuli. c FGJi;Jte papillae: located on the pos~orside$ ofthe tvngue. containIng numerous taste buds.
HftHI -
5. Oral Ccrvffy
Do111m ofiDngue
c
>------ v.rt!GIImuode ofiDngue
)""'.....,..,.~-Th11'1$lootiW
muscle ofiDI'Que
Musclesafthltangue a Left latmsl view. b anterior view ofi coronal secUon. There are two sea of lingual muscles: extrtnslc and lntrtnslc. The extrinsic muscles are ~ched to specific bony slb!s outside the!Dngue,while the inb'insic mt.11cles ~ no attachments with s!Geletal structures. The mrlmlc llngu;d musdes lnd ude the: • • • •
The extrinsic muscles m~ the tongue as 1 whole, while the Intrinsic musdes alter Its shape. Ellcept fur the palatoglossus, which is supplied by the VI!JUS nerve (CN )(), all of the lingual musdes are Innervated by the hypeglossal nerve (CN XJI).
\
D Unllner.l hypogioaoll netwe p•ltr Adlve protrusion ofthe tDngue with an Intact hypoglossal nerve (a) i nd with a unllmral hypoglossal nerve lesion (b). Whe"l the hypogiCJS~al ntn"e is damaged on one side, the genioglossus
musde Is paralyzied on the lffected side. As a result, the heillthy (Innervated) genioglossus on the opposl~ side domiNtes the tongue across
the midline tow~ VIe affectrd side. When the !Dngue Is protruded. therefore, It d~b!s tow~ rd the paralyzed slde.
•
ApadiDnguo
b
105
6.3
Tongue: Neurovascular Structures and Lymphatic Drainage
• A Nerveund-lloltfletDngue • ~ft lateral view, b view of the inferior sur· f.lce ofthe tongue The tongue Is supplied b¥ the lingual arh!ly (from the maXIllary .artery), which diVIdes Into its l!!rminal br~ndtes, the dHP lingual ~rtery and the sublingual artery. The lingual vein usually runs parillel to the irtery and drilns Into thetntrmoi}Ugllklrwtn. The lingual mucosa receives il$ $DmQfosensory innervation (sensi· tMty to thermal and actlle stimuli) from the ltnguol rtMil'. which rs i branch of the trtgeml· nal nerve's mandibcJiar division (CN V~. Tbe lingual nerve transmits flben from the chorda tympani of the f.lclal nuve (CNVII). imong them the .afferent taste ftben for the .ilntel'for two-thirds of the tongue. The chorda tympani aiJO cont
Subllngu;JI iJrtl!ry
Apexoflalgue
An1:2ffor lingual glands
Frenulum
Subtngu;.l fold
--~~
Subtngu;.l
---==--'!!!!~
papilla
b
106
Deep lingual
ilrtl!ry iindwln
H ' - - - - Ungu~IIICS'IIe Sulmllld'bullr duct
HHd -
6. OnJICDVII.y
~~~-=~--G~~~
.-(CNIX}
B Somltosensory lnnll!ll'lllltlon (lefttTde) and tlste Tmermfgn (rtghtshfe}oftheton1Jue Anterior view. The tongue receives Its soma!DsfnSOfY Innervation (e.g., touch, pain, thermal sensiltlon) fn:Mn three crllnlal nerve brindles:
Three crani;ll n~rves llbo convey the tam fibers: CNVII (facial nerve, chordatympanQ, CN IX(glossopharynge..l ~~~ne),llnd CNX(Yagus nerve). Thus, a disturbance oftaste sensation Involving Ule anterior two-thirds d the tongue lndkates the presence of a f.adlll nerve lesion, whereas a disturbance of ucble. pain. or thermal senwtion irldicates a trigeminal nerve lesion (see also pp. 75 and 81 ).
\ - - jugl.fafao:lal
wnous)lnctlan
- - - - lntl!mal )!gular win
>---- jugl.far
•
lyn'Cih nodes
c t¥mphlltl'c drlllnege of the tanguund oral fl_. Wt lab!!ral view (a) lind anteriarview (b).
The lymphatic drainage of the tnngue and oral floor Is medlawd by submental and submirldlbular groups of lymph nodes that ullfmately drllln Into the lymph nodes ilong the Internal jugular vein (a,jugular
b
lymph nodes). Beausethe lymph nodes recellle dr.alnage&om both the ipsilab!!ralllnd conbr.alaterlll sides (b). tumor cells m..y bemme widely dlssanlnilted In this region (for example, metastalk squamous «II carcinoma, especially on the lateral bollfer of the tongue. frequently mebstasi'Zes to the opposite side).
107
Head -
6.4
6. OraiCiwfty
Oral Floor
bmus of monclble
Angltof ----,'11~ mandible
•
HyaglaliSW
--f----"'-------~
~o~d--~----------~--· Dlgastrtc. _
_ ___/
antnr belly
A Mulldauflheol'illftcao Supertorvtew(1) lind left lolltleral vlew(lt). The oral floor is formed by a musrular sheet that stretdles between
the two rami of the mandible. This sheet consists of fvur mUKies, all vf whldl are lot.itEd above the hyoid bone and lire thus collecltvely known as the su prahyold muscles: 1. Mylohyoid: The muscle fibers from NCh side fuse In ll median raphe (cowred superiorly by the geniohyoid).
101
CoiYiectiYe-Cissue sr..g
2. Genloh)'uld: mengthens the central portion of the oral floor. 3. Dl§lllstrlc: The o1 ntertor belly ofthe digastric Is lot.itEd In the orlllfloor region; Its postertor belly llrtses from the mastDid process. 4.. Stylohyoid: arises from the styloid proceu. Its tendon is perforllted by the lntmned~ tendon vf the digastric. All four mu3da participate in Kti~ opening of the mouth. They also elevate the hyoid bone lind move It forward during swllllowlng.
HHd -
'11-~:---
6. OnJICDVII.y
Inferior alwolarneM O!orda tymp.1111
Subrnandbular ganglion
Dl~c.
'-'1!ohyold
antl!rforbelly
T!IQemlnal oan91on Clenlcu~
gangjlon
c MIStold
Mandbl.far dMslon
aels
.~f---
Dlgam!c,
()Oiteforbelly
b
Faclalne~~oot.
Fadal~
st)lolr)oold brwu:h
dljil!ltric b111nch
8 lnMIYol\fon of the ol'il floor muKfi!S a 1St lilterallltew (right half of the mandible VIewed frcm the medial side). b Sagittal section thrac.rgh the foght pl!tnlus bcule at the lew! d the miiStold proan and mastoid air cells, viewed from the medial slcle. c Left later.;rllllew. The muscles of the or.al floor have a ccmplex nerve supply (differ· ent br~nchial arm derivatives) with ccnlributions fram three dilli!!rent
nerves:
a The derfvatllles of the mandibular arch (mylohyoid, antenor belly of the digastric} are supplied by the mylohyoid nerve, a branch of the mandibular division (CN V3}. b The derllla'liYeS d the second br.;rnchlal .;rrch (postenor belly d the digastric. stylohyoid) are supplied by the facial nerve. c Thegeniohyoid (and the thyrohyoid) muscles a resupplied bytheventral r;rml of C1 spinal nerve, whlch tra~l with the hypoglossal nerve.
109
6.5
Oral Cavity: Pharynx and Tonsils
A waldeyer's rTng Pom!rl~r view of the ~pened pharynx. All the components of W..lcleyer's rfng c;m be SHn In this VIew. Waldeyer"s ring ls composed of immunocompetent lymphatic tissue (mnsils and lymph follicles). The tonsils are "Immunological sentinels• suJTOundlng the passageways from the mouth and nasal caVIty to the pharynx. The lymph ~!ides are distributed over ill of the epithelium, showing marked regional wriilttons. W..ldeyer"s rfng consists of the follOWing structures:
• The unpi!lred pharyngeal tonsil on the roof of the pharynx • The paired pal;atinetonsils • The llngu..l tonsn • The paired tl.ibil tonsils (tonslllae tubir1ae). whkh may be thought of as lateral elrtl!n· slonsofthepharyngealtonsll • The paired literill bands
Pharyngeal - ---::::;,....;;.""l!
"'=::'"'-'".......- - lloofof pharynx
tonsil
>--"f-,-7--
Tubal tonsil
~c1f"ue
oflmral bands
----,--..
(u"'ng"'
IT-!::~---;---
Palatine tonsl
"---- -+- - Ungual
pharyngeal fold)
tonsl
Tons11ar fossa U\11111
Palatine
tonsil
a
I Pill.nlne ton Ilk: loc.1tlon ;md ibnomnil enlarg111111nt Anter1orllfewofthe oril caYity. ;a The Pililtlne tonsils occupy a sh.1llow recess on each side, the ton·
slllarfossa, 'Which Is locilted between the anterior ind posterior pillars (palatoglossal arch and pi!latopharynge.al arch).
110
b
c
b 01nd c; The Pililtlne tonsil is examined clinically by placing a tongue
depressor on the anterior pillar ind dlspladng thetonsllfrom Itsfossa while a second Instrument depresses the tongue. Severe enlargement of lfle p;~latine tonsil (due to viral or badl!tial infection, as in tonsillitis) may slgnlflcantly narTOWthe outlet of the oral callfty. causIng difficulty In swallowing (dysphagia).
Choana
---+.~~----~·~ phoryng..l
tonsil
..
a
C Phllryngol tonsil: loutton and abnormal enlargement Saglttill section through the roof ofthe phill'yrwt.
often evoke <1 helghtmed Immune response In the lymphatic tissue, auslng "adenoids" or "polyps.") The enlirged pharyngeal tonsR blocks the choanae, obstructing the nanl airway and fordng the child tD breathe through the maulh. Since the maulh is 111en constandyopen during resplr<~llon ill: rat. an eJCPerlena!d examiner can quleidy diagnose the aclenoldill condition by vlsuill Inspection.
• l..oabi:d on the roof of the pharynx. the unP'ired pharyng~l tonsil an be examined by means of postErior rhinoscopy (seep. 119). It Is p;~rUculilrty well developed In (small) chlldren ;mel begins to regress at 6 or 7 years of age. b All enlarged pharyngul tonsil Is -vay common In preschoo~age
children. (Chronic recurrent Nsopharyngeal lrnctlons ill: this age
llll!!plr.I!Dry
Nanla!mln!ZI!d stntllled
fS)Ithelum
>qUIITICIUS Olllthet~m
~
!
. . -..:.
• #'• •• • '
•
..
I
5e(l)ndary fcllldes
D Htlbllogy of the lympMtlctluue ofthearal cntty and plwynx
Because of 111e dose anatomical relationship between 111e epitheJium i nd lymphatic tissue. 111e lymphatic tissue of W.;ddeyer's rtng InIso des· lgnated lymphoeplthellal tissue. il
"'"""oeplthellill t!Aue. Lymphatic tissue, both orga nlzed and diffusely distributed, Is found In the lamina propria of all mucous membranes and is known as mucosa·associatl!d lymphatic tissue {MALT). The eplthellu m acquires a looser texture, with iibundant lymphocytes il nd mi1Crophages. BesJdes the wel~deflned tonsils. smaller miiKUons ~ lymph follicles may be found In 111e lateral
tf j
OlPtS Stcandary full ida
I
- - - - - Cannec!Mlluueapsule
Rmln•nts ohlaughed
c
eplthellalalk
bands (salpingopharyngeal folds). They extend almost vertically fram the lmral wall to the posterior wall of the oropharynx and nasopharynx. b S'tructure of the pharyngaltand. The muCOSill surface ofthe pharyngeal tDnsll Is r~lsed lniD ridges that greatly Increase Its surface area. The ridga and inb:NtJ1ing crypts are lined by cilimd respiratory epithelium. c S'tnlc:ture of tile Jlll'-tllll! taniiL The surf•ce area of the p;~liUne IDnslllslncreased by deep depressions In 111e mucosal surfxl! (creating an Ktive su rf'Ke are<~ as la'lJUS 300on'). The muC05ill is covered by nonlcrr.rtlnlzed strilt!fled squilmous epithelium.
111
6.6
Salivary Glands Au:us.«y
parotid gland
A Mi)orAIInrygl;mds L
b
112
Facial ar11try
Submandibular
lllldwfn
dand
HHd -
6. OnJICDVII.y
~LYfi!~=---:-- ublal
glands
8 Mlnornllv;uyglands In addltton to the thrl!e ma)or p;~!red glands. 700-1000 m1110r glands also se
C Bimanual ellilmln;atton of tile s;allwilny gl;ands The two s.illllary glands of the mandible. the submandibular gland and sublingual gland, and the adjacent lymph nodes are grouped around the mobile oral floor, and so they must be palp;~ted against reslstmce. This Is done v.tth bimanual examlna!lor1.
Parotid
Superfldal tl:mpo!'
tllmor
<~~<~ndwln
I
J I
I ( Jugular
lymph nodes
I
HypogloJsal nerw Slbmand~
I
~}
Fiitlalnsw
\
\
blllarl)mph nodes
P.rotld pluus
Atdalnsw
ln!J!ITIII Jugula-vein
D Spretd of mlllgn1nt p1rvtld tumon 1lo09 ulltomkll ~ Malignant tumors of the parotid gland may directly ln11ade surround· lng structure.s (open arrows); they may also spread vla A!glonallymph nodes (solid arrows), or spread systJ!micllly (metastasize) through the vascular system.
Parctld gland. d~p;rt
51:2mocleldomastoid
E lntragl1ndul1rG1urse of tile f.lldll nerve rn the p1rvtld gllnd The facial nerve dMdes Into branches 'Within the p;~rotld gland (the parotid plexus sep;~rates the gland Into a superflclal parund deep p;~n) and is vulnerable durirlg the surgical removal of parot!d tumors. To preserve the facial nerve during p;~rotldectomy, It Is flrst necellSary to loc
113
Hettd - - 7. Nose
7.1
Nose, Overview
""-'-...;_-~:----.-""---:-"r--- ~lcular
Mldde - --+...;;-.nasal concha
plate of
7-':......:=--:-::-=- -
ed!mold bone '-\,_;::-,~~~~~-
lnfr410rtl1<11nenoe
- --:--:---:---:f-- - M;aclllarysl'nUI
CJrthuklous
----''o--~~..,....:.=-----7.;.-.::~
oiiSolll~
--~---~~~~--~~ nasal concha
~~--~~L-~L___ ,~
nasal mea1US ~-.......-'~,....-------".------
Alwdar proaem;
•
I
Tongue
Onllcl1111ty
b
A OW!rvlew afthe nll:lf! and p1ranaul sl'nules Coronal section. antel1or Ylew. b Transverse section. superlor11iew. The re;rder Is assumed to be famllrarwlth the bony anatomy of the nas.ill C.i111lty(especlallytlte openings of the various paSs.ilge.s ~the nas.il amchae, seep.19ff). The nas.ill cavities and par.anas.ill sinuses are arranged ln paii'J. The left and right nasal c<~Yit!es are separated by the nas.il septum and hive an approximatEly triangular shape. Below the base of the triangle Is the oral cavity. The follo"fng pained paranas.il <11
sinuses are shown in the drawings:
114
• Front.'!l sinus • Ethmoid ails (etflmold sinus•) • Mildllary sinus • Sphenoid srnus The interior of each .sin LIS is lined with ciliated (seep. 118).
respir<~tory
epithelium
• The term •ethmoid sin LIS• hilS been dropped from the l;atest anato-
mical nomenclature, iltttough It Is stlll widely used by medical practitioners.
HHd - - 7. Nose
Sphenoid
31nus
1\las.il - --."'"---,......--~
s.tj)tum
Phorynllt
o~dpharyngo
t)mp;uict\lbe ..,..,_.......,~ Oensd m
Soft palm, palallneseptum S9henokl
sina
Umennasl
b
B Muco:u of the n.~~~l arutty
Middle niS.lllax1cha ~~----,::.....;:;'---Cho;Jna
("I)OStA!rior naris')
P.alatoph;lr)'ngeal
Tongue btlse - --':-oojol.,_,_;. wlthltngUII
tonsil
'""
,.;;r--=--.,.--- tM.I~
a Mucosa af the nasal septum, parasagittal section 'riewed from the left slde. b MucoJa of the rtght lmrosl nasal wall. viewed from the left side. c Posterlorvlewthrough !he cho;mae intD the nasal c.avity. While the medial w.rll of the naJal Ci!VIty ls smooth. Its lmrill wallis raised Into folds by the three conchae (supenor, middle,. .and inferior conchil). The~ incre
115
Pilras.1glttal section, viewed from !he left ski~. The .-.rteffal supplyofth~ nill!al $eptum Is of partiCIJiar dlnkallnterest In the dlagn0$1s .mel treatment of noM!blftd (see C).
B Ytsselund nerwsaftflelfghtlltil!ral n~~~alwal Left l~teral view. The ~rntop~l~tine ganglion, an import~nt relay in
tfle par.ssympilthetlc nervous systEm (seepp.81 and 101), hils bftn expo~ herebypartlill re~lon ofth~sphenold bone. The neNeflbers arising from It pill!s to the small nill!al glands of the nasal coDChae, entering the condl;!e from the po$terior side with the blood ~"els. At
116
the level of the superfor concha, !he olfactory fibers pass thrcLJgh the cribrifonm pl;ate to the olf.lctory mucosa. The n;~salwall is supplied frvm above by tfle two ethmoidal arteffes, whldl arise from the ophthalmic artery. It Is supplied from behind by the later.~l postertor nasal arteries. which arise frcm the sphenopalatine artery.
HHd - - 7. Nose
Thefiguresbelowdepictthdunctianal groups of ~rtertes and nerveJ supplying lfle nawl cavIty. As rn ~ dlssecUor1, the septum Is displayed flnt. followed by the lateral wall.
c
Artertes ofthe 111111 ~m left lateral view. The ft.JSels of lfle nawl septum arise from branches of the exter· nal ;md Internal e<~rotld ;uunes. The ;mtenor p.art of the se¢llm a»ntlins a highly vascularIzed a~ e<~lled Klendbach's area Undlcmd by color shading), which Is supplied by vusels from both major i111:erles. This ilrt'a Is the most mmmon slt2 of slgnlfle<~nt nosebleed.
~btach's
- -++-..-; ,;:;
lftl1l
Olf.xtory
CrtH!fomlplm
bulb
afetflmoldbone
D Ncm:softheniAI septum
Ophtllllmlc
left lateral view. The nasal septum re«llles
dvtsfon
Its sensory lnneN.atlon from branches of the
trigeminal nerve (CN V}. The anterosuperior p.art of the se¢llm Is supplied by branches of the ophthalmk dMslon (01 V1), and the rest by brioches of the maxillary dMslon (CN V1). Bundles af olfactory nerve fiber$ (011) arise from receptors In the olfactory mucoJa.
...;;!-::::...._-
Trigeminal 91f19llan
c.dlaglnous naniS1!ptum
Medial supetlar ~ornanlbr¥lches
(maldlarydMsiOn) VGmer
Mallia
Nasop;lla!lne ntNt
~arna11c
proa!.SS
t-.;;o..::::::,..~;.,....- ~
~----"'-l''lo'
l)llitflll!
!llnglion
Inferior pomrior nlllll bnlnch!s
l.atl!
E
Artertesaftfu~rtghtlltil!nl n•sal-11
Left lateral view. Norethe v.ssCIJiar supply from the branches of lfle Internal c~rotld ar1:ery (from above) arid tile external e<~rotld ar1:ery (from behind).
I!Umll nasal
Inferior
brandies
ni!WIICIXlchl
F NenltSaftMrfghtlatenl n1saiWIIII Left lateral view. The nawl wall derives its sensory innervation from brancheJ of the ophthalmic diYislon (CN V1) and the rnaxlllary dMslon {CN V:z). Receptor neurons In tile olfactory mucoJa send their axons In the olf.actory nerve (CN I) tD the olfactory bulb (seep. 179 E).
117
Hettd - - 7. Nose
7. 3
Nose and Paranasal Sinuses. Histology and Clinical Anatomy ~--Kinodlll·
belling epith'!!IIIICII!Is
_ _..:..___,,.,.--- -
-
A hnctlom•lmtesofU!emiiCDSillntfll!nuOII c;Mty Coronal set:Uon, ;mtertorvtew. The 11Jnction of the nasal mLJCosa is tD w.lnn and humidify the inspired air. Thlsls accomplished by an Increase of blood flow through the mu· cosa (seepp.S9 and 61), piKing It In a congested (swollen) mte. The mucous membranes are not simultaneously congi!SU!d on both sides, hOWC!IIer, but undergo a normal cyde of a~ngestian and decongestion tf!at lasts approxlmately 6 hours (the right side Is decangested lr1 tfle drawlr~g). Examlflatfon of !he nasal av1ty nr1 be fadlltlted by first ad· ministering a cleconge.sunt to shrink the mucosa, roughly as It apJ)elilrs here on tht- lt-ft sidt-. l'fon!al
sinus
Etlmold
Sptlenold
s'rlus
sinus
.:.....;..~~- Fbrouslamln;~
prop!la
NISII~m.
8 Hlltologyof the niiSal muCOR
The sumce of the pseudostratlfted respiratory epithelium of the nasal mucosa consists of kinDCilia-be..aring cell$ and goblet cells, which secrete their mucous Into a wamy film ar1 the epithelial surf.!a. Serous and seromucous glands are embedded In the connectfvetlssue ;md also release secretions Into the superficial fluid film. The directional fluid flow produced by tht- cil~ (see C and D) is an importlnt companent of the nonspecific immunt- response. If coordinated beat:!r~g of tfle dlla Is Impaired, the p;ll:lentwlll suffer chronic recumng Infections ofthe resplrlltDrytract.
Oslfum
\
Pomrtar Willi
offronl.llsfnus
- - - 1\lasopharynx
Medlalw;ail of m.lillhrysfnus Eltlmold
b
C Nannnll dratnage of t«rl!tlant from tfle piNIIIUl tlMil
l.dt latera111iew. The beating dlla propel the mucous blanket over the cilia and through the swaiiOI!tt'd.
choar~a
Into the nasopharynx. where It Is
lnti.ndbllum
D Dlredlon afdlary bdtfng and fluid f l - In tfle rtght mullllryslnuJ 1nd frontal sTnuJ SchernaJSc coror~al sections of the right maxillary sinus (
tides and microorganisms thlt ire tripped In the mucous layer. If the ostium Is obstructed due to swelling of the mucosa, Inflammation may develop in the af!Rted sinus (sinu!itiS). This oa:urs most commonly in the ost!omeaul unit« the maxillary ~lnt.IS-dhmold DSI:!um (see pp. 20 ;md 21) (ifter St
111
HHd - - 7. Nose
F IE'ndoscopy of dta mulll;uy llnuJ
Anterior 1/few. The maxillary sinus Is not ilc:cesslble to direct Inspection .md mustthe!'efore be examined With an enclosco~. To enter the maxlll;lry sinus, tfl~ ex.;rminer pierl%5 the thin bony wall below the inl'l!rior cond!i wlth atroc
a
a Antllrtorrfll.-pybaprocedureforlnspectlonoftflemsalcavlty. Two different positions (1.11) are used toensure that all oftile anterior niiYI a~~tty Is examined. b In p-rtor rfll.-.:opy, the chD.'!nae and pharyngl!ill b:lnsil ane <~ccellSible to cllnle
b
An!J!rletll1d poMicr
tthmolclll 11tsfes Orlllt
lnfraorb!t.11 foramen
G Slta d arterllll llgalfon fordte tratment of severe nosebleed If a severe nosebleed e
scope.
119
Hettd - - B. Eyuntl Orbit
8.1
Eye and Orbital Region
SUpr.IICirbllalartl!ly
Dorsal nasal
andne~~~e
arlltryandwln
lnfraorbltllnln'e and arlltry
~palpebrae super~orts
Fad'al artl!ly
Orblcularts a run. palptbral part
Angular artl!ly
Medial palpebral
and vein
tgament
Nasalis
alaequenasl
SUpraarbltllartl!ly SUpraSuperior and neM !rodllear ntNe obi~
A Sclperftd;ll ~nd d18p MUI'OIIiiiiCUYr structures afthe orflltill region Right eye. anttrforVIew. • Superficial layer. The arbiUI septum on the right side h;ss b~ eJq>osed by removal Clf the orbicularis oculi. b Deep layer. Anttrlor orbltoll rtructures hill/e been exposed by partial removal of the orbitoll septum. The regions supplied by the lnmnal carotid artefy (supr.ilorblt.ill artery) and ext!mol carotid artery (infraorbital artery, f.atial arlzry) meet In this region. The anastomosis between the ;mgular vein (extr.ilcranliiO and superior ophthalmic wins (ln1racranlal) creates .il port.ill of entry by1M'Iich miaoorganisms may reach the c<1vemous sinus (rlsl:of sinus thrombosis, menIngitis): therefore It Is sometimes nec:ess.ilryto ligate this an;sstomosls In the orbital region, as In patients wnn extens11te Infections of the exmnal fadill region(~ p. 93). Nob! the paSS.ilge of the supr.il-.ilnd lnfraorbltoll nerws (branches of CN v, and CN V2) through the accordingly named foramina. The sensory function of these two trigeminal nerve divisions can be tested at these nerve exit points.
8 Surhcun;rtomyoftfleeye Right eye, an1l!rlor VIew. Th~ measur1!1Ylents Indicate th~ Meith of th~
normal p;dJ)C!bral fissure. It is impartlnt to rm- tflese measurl!mC!l'IU because there ine a number of diseases In whkh they ine altered. For example. th~ palpebr.ill tlssure may be -widened 1r1 peripheral f.ICial paralysis or narrowtd in pmsis (• drooping of the eyelid) due to OClllomotorpalsy.
Jmm R--Medlill : anlllus
. . .
_....:
of~lcls
"-t eyefkt
I.A!v.atorpalpsuae supe!lells
Orbit!I
SEptum
Si.pl!fler rectus Si.pl!fler
Orblallarts
co!lunctMII fomlx
oculi.
orbltollpart
Si.pl!flert3rs.ilmusde Si.pl!flerbl rsus with blrsal~ands
r..ens
Upper eyelid
Co mea
SUper'lor forniX
Iris
Olillrybody lnll!r!or tir!IIJ
OOJ!ar alnjunct~
~ha
Sden
l.owoer
lnferlcr1:3rul muscle
~·d
c Structwuftfle eyelids and CDn)unr:ttva Sagltt.ll sed!ontflroughtheantl!riororbltalc;Mty.b AnatomyGfthe
junctiva (tunica conjunctiva) is a vascularized, tflin, glistenir~g mucous membran~ !hat Is SIJbdiVIded lntDthe polpebrol con}!.rr!cfMI (see above).
CDnjunctiva. Tbe eyelid consists cllr~leo~lly of .iln outef and ifllnner layer With the fol· lowing mmponents:
fomlall a>n}unctM1. and ocular con)ullCINa. The ocular conjunctiva bar· ders drrectly on the comeal surf.a~ aDd combines -w!lh rt to form the c:on)unctfwiiHc, whose furlCtions iACiude:
• Outer layer: palpebrlll skin, 1WI!.lt glands, dllary gllloos (• modlfted $we>lt glands, Mall glands), Mili!a!OUs glands (leis glands), aDd twll siJ!ated m111des, tfle orbicularis oculi and levatxJr palpebr;~e (upper eyelid only), rn~Mted by the f.ilclal nenoe .iiOO the oculomotor nerw,. fl!SI'ectM!Iy. • Inner layer: the tarJUS (flbrous tissue plate), the superior aDd Inferior Wsal m111des (of MDIIer. !lmOOtfl musde Innervated by syrnpatfletlc fibers), the tarSil or paiJ)C!bral conjunctlll.il, and the tarsal glands (Meibomian glands).
• fllclllt.rt!ng ocular movements, • enabling painle$$ motion of tfle paiJ)C!bral conjunctiva and ocular cor~junctlva relative to e
;a
~ularbllnklr~g (20-30 times per minute) keeps th~eyes from drylfl!l out by IMnly distributing th~ lacrimal fluid aoo glandular secretions
f/&. which also serves to protect the mrnea and con)unctMt. Th~ con-
Th~supenor .ilnd
lnli!lforfornlces .aneth~ sites ~Mlerethe conjunctllla rs from the upper and IOWI!r eyelid, respectiw.ly, onto th~ ~ ball. They ane mnvenlent sites forth~ Instillation ofaphthilmlc medkatlons.fn/lammat:lon aftheconjunctNa Is mmmon and COIII!es a dilation of the mnflJnct!val vessels resultlfl!l rn "pink eye.• Convenely,ll deftdency of red blood cells (anemia) may lessen the prominena oflliiScular marie· lngs In the conjunctiYa. This Is why the conjunctiYa should be routinely Inspected In every dlnlcal examination. ~ted
121
Hettd - - B. Eyuntl Orbit
8.2
Eye: Lacrimal Apparatus
lnfr.Joltltill fo111men A laat'mll apparat111
Right eye, antzriorview. The orbibl Hfllllm has been partially l'l!!moved, and the wndon of Insertion of the lev
122
along arteries to reach the lacrl'mal gland. The paras.ympathefk lnnerlliltion of the lacrimal gland i$ complex ($Hp. 81). The llaimll appamus can be understood by tracing the fltM of lacrimal fluld obllq~~ely downward from upper right to lower left. From the superior and Inferior punellt !he lacrimal fluid enters the super1or .and lnfertor /acrfmo/ con a· liaJ/i, which dil'l!ct the fluid into the locrimGIsac. Finally itdrains through the narorocrimal duct to an outlet below the Inferior conma ofthe nose. "Watery eyes" are a typical cold symptom caused by obstruction of the Inferior opening ofthe nasolacrimal duct.
-
NIISIII
. -: ~ ~: .
.. :
...· . 8 Dllt.rtlutlor1 of 90blat ceiiJ lr1 the cor~!WICIMI (ilfter Cllabria and Rolando)
Cobletcells .are mucous-sec:relfng cells With .ilfll!pllhellal cOIIelfng. Their secre&tu (muclm) are ar~lmportant cx:~nrt!tiJent of !he lacrimal fluid (see C), Besides the goblet cells, mudns are also secreted by tile main lilcrimal gland.
D MKh;mlc.JI propulslor1 ofthelacrfnwUUd Dutfng do sure of the eyelids, cx:~ntrac:Uon of the orblaJiarts ooull ~ ceeds In .a tempor.al·to·nasal dlreclfofl. The successiVe cx:~ntraclfofl af the5e muscle fibers prvpels the lacrimal fluid toward the lacrimal passages. Noll!: Facial paralysis prewnts clcsure of the eyelids, causing the eye to dry out.
Lipid layer, apprax.O.lJim
b
c
C Struduruf the tar film (ifter IAr~g) The tear fllm Is a complex fluid With sevetal morphologlully distinct layers, whose cx:~mponents .ilre prodOO!d by IndiVIdual glands. The outer lipid layer, prodOO!d by the Meibomian gl;mds, prvtecu the aqueoU5 middle layer of the tearfllm frvm eYapora!lng.
tnferforlaafmal C
Comncn lllalnwl
an.wlk:ulus
E ObstrudlofiJ to l.a:Tm~ll driiMge (after Ling) Sites of obstruction In the lactfmal dralr~age system car1 be located by Jrttgatlng the system with a special fluid. To make this detennlfl.iltlon, the ex;aminer must be f.amiliarwith the anatomy of the lacrimal apparatU5 and the normal drainage pathways for lacrimal fluid (see A). a No obstruction to l;lcrimal dr.rinage (cx:~mpare with A). bifid c Stenosis In the Inferior or common i;lcrlmal car~allculus. The stencsls causes a damming back aflaafmal fluid behind the obstructed site. Ill b the fluid reflwa!S through the inferior lacrimal canaliculus, ind ln cIt flows thrvugh the superior lacrimal car~alloulus. d Stenosis below Ute level of the lacrimal wc (postlilcrimal s.1c sten~> sis). When Ute enure laatmal s.1c has fllled With fluid, the fluid begins to reflux irlto the superior lacrimal canaliculus. In such cases, the lacrimal fluld often has i purulent. gelatinous appeilrince.
123
Hettd - - B. Eyuntl Orbit
8.3
Eyeball
Ocular -----,~ con)lndflla
~0~---~~~----------~~ fo:sR
tUtUS
A lhii'IM:f'Se scdlon through the ~II IUght eye. superior view. Mort of tile eyebillls composed of lhree concentric layers (from outside to Inside): !he sden, choroid, and retina. The anb!!tior p«tion of the eyl!!ball has a diffen!nt sb'ut:Wn!, howevl!r. The outllr COilt of the eye In this region Is formed by the comN (ante· rlor p«tlon of tile fibrous eDit). A'S !he •v.1ndow of the eye." It bulges foJWard while COY«fng !he strut:Wres behlfld lt. At the corneoscleral limbus, the come<~ is continuoU5 with the less a~nvex sdt1111, which is the porterlor portion of the outer coat of!he eyeb
124
The Iris shields the eye from exce~IYe light (seep. 128) and covers the lens. Its root Is continuous wllh the ciliary body. which contains the cllrary m111de for wual accommoclatlon (a tilers the refractllle power of the lens. see p. 127). The epithetium of the c1iary body pradi.IC!e$ the aqueous humor. The dllarybadyls contlnuous<~tthe ora semta with the middle layer of the eye, the dtorokl. The choroid organ Is !he mllSt highly vascularfzed region In the body and serves to regulate !he tem· per;~t\Jreoftheeyt>and tuupplyblood to theoutC!I'I~rs of the retina. Thelnnerlaywofthe eyels the ...Urlil, whlch Includes
poral to the optic disk. Incident light Is normally focused onto the fofta centra lis. which Is !he site of greatest wual acuity. The rntertor of the eyl!!bill is occupied by the vltn!DIII hum11r (vltfto~a bDCfr, see C).
Site ohttadlmentto 0111S
ba!ieofSalzmaM)
B lll!fei'II!IIICe l1'nes and poTnts on the f!111: The line marking the greatest drcumferenct' of the eyeball Is the equa!Dt. Lines perpendlaJiar to the equiltOr are ailed lllflldlatts.
Normal (emmetroplc) eye
C Vlln!oul ~ (llttn!DUl hum«) (after Lang) Right eye, tramverse sectior1 viewed from above. Slm wflere the vl1:reous body Is itt.1ched to other ocular structures are showr~ln red, and adjacent spaces are shown In green. The vitreous body subii!Zes the eyeball and protem against retinal deuchment. Devoid of nei'YC!$ and vessels, It conslm of 98:1: w.rter and 2:1: hyaluronk add and collagen. The "hyaloid canal" Is an embryological remnant of the hyaloid irtefy. For the treatment of some diseases, thellttreous body mq be surglc.llly remcwed (vinctomy) and the resulting avity filled with physiologial salfne solution.
lnddlnt
llghtni)'S
/
I
i
l.
D light refrutlon Tn a nonn1l (emmetrvpk) CJI!Ind In myopTa
n!Cius
01nd hyperopia
Par.allel rays ftom a dlsunt lfght sou ret' are norm.ally refr.acted by the CDmea and lens to a fDcal point on the retinal surf.!ce. • lrl myopia (neanlghtedness), the rzys are focused to a point,, front of the retina. • lr1 hyperopia (fal'llghtedness), the r.~ys are fDcused brhlndthe retina.
E Optlc.~l ulnnd orflltai..U Supaforvlewofboth eyes show!Dg the medlal,lateril and superior recti and the superior oblique. The optfal axis deviates from the orbital axis by 2l'. Bee! use of this disp.2rity, the point of maximum visual acuity, the fO\'e'ilcenmlls,b lateral totfle "blind spot• oftheoptkdlsk(seeA).
125
Hettd - - B. Eyuntl Orbit
8.4
Eye: Lens and Cornea
A OftMew: Posltfon ofthe le111 and CDI'Ma lrt 1M eyeball Hirtlllogical section through tbe c:cmea, lens, and suspensory ~pp~ratus of tbe lms. The nor· ~I lens Is dear and tr.msparent and Is only 4mm thick. It Is suspended In the hyaloid fos:sa of tbe vitrecus body (seep. 124). The lens is at· tached by rows offlbrils(Z!Inularflbm)tothe ciliary muscle, whose contractions alter the shape ;md focal length of the lms (!he strucwreoftheciliarybodyisshown in B). Thus, the lens Is a dyn~mlc strucwre that can dlange Its shape In response to visual requirements (seeCb). The anterior chamber of !he eye Is situated in front of the lens, and the posterior chambEr Is locatl!d b~ the Iris and the anterior epithelium of the lens (seep. 128). The lens. like the vitreoUs body, Is devoid of n~ and blood vessels and is composed of elongated epithelial cells, the lens flbm.
f'QstJ!flor
Ills
chan'b!f
a~J~ ~
lllrspillla
lllrspllab
ll:>nular flt.rs
Epltht!l\lm of dllrybody
T~ular
meshworit
Iris
Olarybody, parsplcm
I The lmnnd dlllry bodr' Posterior view. The curvature of the lens Is regulated by the muscle flbm of the annular dll· arybody(seeCb). Theo't,IQI)'bodylies between the ora smrata and the root of the Iris ~nd con· slsts of a rdat!vely flat part (pars plana) and a part that Is raised Into folds (pars pllcata). The latter part i$ ridged by ap~matl!ly 70-80 radlillly.oriented ciliary processes. wfllch surround the lens lila! a halo when viewed from behind. The dllary processes c:cntaln large capillaries, and tneir cpitnelium -retes tbe aqueous humor (seep. 129). Veryflne zonular fibers extend from the bas.1l layer of the ciliary processes to the equ.ator of the lens. These ft. bm and tne spacu between them conJtitub:! the suspensory apparatus of the lens, called the zonulf. Most of tne ciliary body Is occupied
126
Ohryprocrs.ses
Cllarymwde
by the o1i;rry muscle, a smooth musde com· posed of meridional, r.ldlal. and drcular fibers.
It arises mainly from the scleral spur (a rein· forclr)!l rtng of sdera just beiCiw 1he canal of Stfllemm), and it atbches to $trlletllres inclu· ding the Bruch manbrane qf 1he choroid and the lnnefsurf.lce of the sder.t. When the ciliary
Ora-
musde contracts. it """' tne cfloroid farward and reliiXI!S the zonular fibers. As these fibers become lax, the Intrinsic resilience of the lens causes It m assume the more convex relaxed shapethrti$ne«S$aryfoc'nearvi$ion(seeeb}. This Is the basic mechanism of visual ~ccom modat:lon.
ChrymuKie reiDed, zonular flben tense,
lens fbttened Llght~lndlltlnt
aa:ammod&lan
Postl!fl«
pole
Clla ry l1lll5de Oll1tra tied. :i:llOtluftberslill,
• c
lens men rouncled
lll!fei'I!IICeli'nes and dplml£~ oltfle ll!ftl
a PrtndPlll miii'Wiw lln•oftfl•lans: The lens has an antmorandpos-
tllrlor pole an am passing between the poles, and ar1 equator. The lens hili a blccrwex shape v;!th a gneater r.ildlus of curvil1llre pcster1cu1y (16mm)th.iln interiorly (1 0 mm).lts function is to tr.ansmit light r<~YS and make flne adjllltments lfl refraction. Its refractift power r;mges from 10 to 20 dlopters, depending on the state of iiCcommodatlon. The ccme111 hili .il consldmbly higher refracttl/e power of 43 diopters.
Embrycnlc nudt<4
b LTght relnu:tlound dynamics of tile lens: • Upper half of diagram: fine adjustment of the eye for for Yisfon. Parallel light rays arrtve from a distant SOCJrce, and the lens Is flattened. • Lower half of diagram: For Mrlr visKJ.n (accommodation to objects less than 5 m from the eye), the lens assumes a more rounded shape (see B). Thlsls effected by contri1Ctlor1 of the ciliary muscle (par.asymp;ltfletlc lnnerv.iltkln from Ul~ oculomaC»r nerve), causing the zonui;lr fibcn to rel;vt ;and allowing the lens to assume a more rounded shape because oflts Intrinsic resilience.
Slr.ltlfled nonb!r.!Unlzed
.squamous eplthellum
•
Ad lit nucleus
0 Growth oftfle lens and ZOMI of diiiGIIIti'IIUity (aftef Ung} a Anterior view, b la1zral vii!W. The lens cont1r1ues to grow throughout life. doing so In a manner oppo· slte to that of other epithelial stnJctunes. I.e .• the youngest cells are at thesurfaceofUielens ~lletheoldestcells.ilre d~er. Due to the constant proliil!ration of epithelial cells, which ;are all firmly incorpora1zd lr1 the lens e<~psule, the tissue of the lens becomes Increasingly dense with age. Asilt-lamp examln.rtlor1 will demonstrate 210nes ofvarying cell density (zones of dlsconlfnulty}. The .zooe of highest cell density, the embl)'on~ nucleus. is at tfle cenb!r of the lens. With further growth, it becomes surrounded by the {mil nucleus. The ln{ont!k t1UCifus dewlaps after birth, .ilnd flNIIy the adult nLtdeus begins to form during the third decade of life. The.se210nes .ilrethe b.ilsls for the morphologlul d.wlflution of c.maracu, a structural alteration in the lens, causing opacity, tmt Is more or less normal In oldage(pmentlr~10~ofall80-ye
E Stn1ctur. of the cornu The cornea Is eoftred externally by str.rtlfled,I'IOilkefatlnlzed squamous
epithelium whose bilial !;Imina borders on the anterfor llmllfng l.ilmlflil (84:Mman membrane}. The stroma (substanti;l propri;l) makl!s up approxlmately 90X of the corneal thickness ;md Is bounded on Its deep surface by the posterior limiting lamlrlil (Descemet membrane). Beneath Is a single layer of ccmeal endothelium. The come.il does have a nerve supply (for corneal reflexes) but it is not lli!llcularized and th~ fore has an Immunologically privileged status: normally. a corneal transpia fit un be perfonned without fe.ilr of a host rejectlor1 response.
127
Hettd - - B. Eyuntl Orbit
8.5
Eye: Iris and Ocular Chambers
lrfs
Pupllary lphtu:t2<
\
Ollarybody
Zcru.iar flbelll
Sclera
Lms
A loc.tUDn ofdie Trtt nd ttl~ 1nterfDr and posterfDr chambers Tr;~nSYe
RCtian through th~ ;utt~rior segment af the eye. superior 1/iew. The Iris. the choroid, ;rnd the dllary body at the periphery af the Iris ilre p;rrt of th~ uveal trict. In the Iris, the pigments ire form~ that determine eye color (seeD). The lrts Is an optical diaphragm 'With a central aperturt>, the pupil, pia~ in frvnt of the lens. The pupi1 is1-8 mm In diameter. It constricts on contraction af the pupillary sphincter (Jxlrv· sympal:tli!!X: Innervation ~a the oculomotor nerve ind dllary ganglion)
;rnd dl'latts on contractfol'l af the pupillary df'la1llr (sympotllettc Innervation frvm the superiarcenlic:al ganglion vi;! the internal uratid plexus). Together, the Iris ;rnd lens separm the ;rntertar c:Nmber af the eye frcm the porterlor chamber. The postertor chamber behind the 111s Is bound~ posteriarly by the vitreous body. centr;rlly by the lens. and lilt· erally by the dliary body. The anterior chamber Is bound~ anta!orly by the corne;r ;rnd postl!rtorly by the Iris ;rnd lens.
c c.- cl miDik and m,drtalls
.,
(after S
...,..,, Ught
b
B PUpl111Zl1! Normal pupil size. b m
121
c
and seNa mainly to optimize visual acuity. Norm;rlly. the pupils art> clra.lar In shipe and equal In size (3- 5 mm). Virlous Influences (llstl!d In C) may cause the pupn size to vary Ol/l!!r a range frDm 1.Smm (miosis) tD 8mm (mydriasis). Agremrthan 1-mm dlscrep;rncy of pupil size bei.Weal the right ind left eyes Is called aniSOCOIIa. Mild anisocoria Is physiological in same indiwals. 1'\Jpillary mlees such as convergence and the consensual light response are described on p.362.
Sleep. fatigue
Paln,el«rt.ement
Miotic ilgEOI$
Mydrfiltlc ~gents
(parasympathl> mlmetia, sympatholytles)
{parasympattlolytles such as atroplnl\,
sympathomlmeUcs such as eplnl!phrlne)
Homersyndrome (including p1Xllis
OoJiomotor P<~lsy
~nd
palpebl'ill llssurt>) General
Migraine alt.1dc.
~nesthe.sta.
glaucoma .tttack
morphine
D St.ructu... of the Iris The basic structural fr;amework of the Iris Is the vasculartzed stroma, which Is bounded on its deep surfac:t> by two !;ayers of pigmented lrts epfttteUum. The loose. colli!Qen-c:ontalnlng stroma of the 111s contains outer ;md lnnervascularcircles (greater and letief' arterial circles), ~lth ;are lntem~nnected by small anastomotlc;artertes. The pupillary sphincter Is an ;annular muscle loc;ated In the stroma bordering the pupil. The radially disposed pupillary dilator Is not loeilted In the stroma; rather lt b composed of numerous myoftbrfls tn the lrts eplthEilum (myoeplthellum). The stroma ofthe lrts Is Pl!fll'l!ilted by pigmented connect!llssue cells (melanocytes). When heilvlly pigmented, these melanocytes of the anterior borderzoneofthestromarenderthelrlsbrown or •black.• Otheswise,. the charilctefcstics of' the underlying stroma and epithelium determine eye color, In a manner that Is not fully under-
PUpiiLlry
dilator
stood.
Anterior
Co mea
chambe"
•
Zonular flbers lrts
\
E Nonn~l dl'ilnillfll! of ;~queous humor Tbe aqiii!OUS humor (~pproxlmately 0.3 ml per ey~!) Is ~n lmpoi'Unt detznminant of the intraocular ptessure (see F). It is pnxii.ICI!d by the n~:~n plgmented ciliary epltttellum of the ciliary proresses ln the posm1or
chamber (appi'Qltlmatz!y 0.15 mlfhour) and passes through the pupil Into the olltl!dorchamber of the eye. The aqueous humor seeps through the spa= of the tr.lbecular me:shworic (f'Gntana spate$} in the cham· ber angle ;md enters the canal of Sthlemm (vmous sinus of the sden). through wltlch It dr;alns to the eplsderal Yelns. The dr;alnlng aqueous humor flows toward the chamber ~nglealong il pressuregradlent (ln!raocular pre$Sure •15 mm Hg, pressure in the episcleral veins • 9mm Hg) and must sunmount a physiological resistance ilttwo sites: • the pup/llofY mlstuOOi!' (between the his and lens) ;and • the trobtatlar reslstl!OOi!' (naiTOW spaces In thetr;abecular meshwork). Approximately 85% of the ;aqueous humor flows through the tr;abecular meshworlc Into the c;anal of Schlemm. Only 15% drains through the uveosderal vascular systl!m lntothewrtfcal veins (uvec.sclml drainage
F Obstrudfon of aqui!IIIKII chl111ge •nd glluCDma The nonmallntraocul;ar pressure ln adults (1 5 mm Hg) Is necessary for a functioning optical system. p;~rtly beCilu5e It maintains a smooth curvaI:IJre of the corneal surface .and helps keep the photoreceptor cells In contilct with the pigment epithelium. When glaualmo il> present (5ee D,p.127}, the intraocular pressure i$elevated ;~nd the optic nerve becomes CDnstrlcted at the lamina afbro5a, where lt emerges from the eyeball through the sder.a. This constriction of the optic nerve eventually leads to blindness. The elevated ptessure is caused by an obstruction thilt hampers the nornn;al dr;ainilge of aqueous humor. whkh c;an no longer overcome the pupillary or trabeo.ilar resistance (5eeE). One of two condiUons may di!YI!Iop:
• AaJre or angle-closure gloucomo (a), In whkh the chamber angle Is obstructed by lrts tls$ue. The .aqueous fluid c;annot dr;aln Into the ;~nterior ch~mber ;~nd pushes portions of the iris upw.~rd, blodcing the chamber angle. • Chrw1ff or open'(lngk gloucomo (b), In wltlch the chamber angle ls open but dr;a!nage through the tr;abeoJiar meshwork Is Impaired (the red b.ar marks the location of each type of obstruction). By far the most common form (approximately 90% of all gl;aua~mas) Is primary chronic open-<~ngle glaucoma (b). wltlch becomes more prevalent after 40 years of age. The prtmary goal of treatment Is to Improve thedrainageofaqueous humor(e.g., with parasympathomiml!l:ics that Induce $UStalned contr;actfon of the ciliary muscle and puplll;ary sphincter) or decrl!ilse Its production.
route).
129
H«Jd - - B. Eyetmd Orbit
8.6
Eye: Retina
No
11!11na
Oplltplllrt afl'fiiM
Mltula Iuta
A Onnfew of the l'lltTN The retina ls the third, lnnl!lmost layer of the •ball. It consists mainly of a photosensitive optic port ;md 11 sm<~ller. non-photosensitive forw11rd prolongation !Allied tl!e nllllllfwcll mlnfl. The optic part of the retlnil, shown here in yell-. wries in thickness a different lo!AItlons. It owrlies the pigment epithelium ofthe UY9I tr.lct1nd Is pressed iiJ!IIInst It by tl!e lntraoClllar prewn. The optic ~ of the retina cncb
Opllc:dlslt
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