Head and Neuroanatomy (THIEME Atlas of Anatomy)

THIE ME Atlas of Anatomy Head and Neuroanatom y

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

MarkusVoll KariWesker 1182 Illustrations 72 Tables

Thieme Stuttgart · New York

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

Plus Version -Includes online access to WlnklngSkull.com PWS

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

Table of Contents

Head

Cranial Bones

4

1.1

Skull, Lateral View ........•....•..........•.....•....• 2

4.1

Overview of the Cranial Nerves ........................ 66

1.2

Skull, Anterior View .......•....•..........•.....•....• 4

Cranial Nerves: Brain stem Nuclei and Peripheral Ganglia••• 68 Cranial Nerves: Olfactory (CN I) and Optic (CN II) .•....•.. 70 Cranial Nerves of the Extraocular Muscles:

1.3

Skull, Posterior View and Cranial Sutures •....••....•..... 6

4,2 4.3

1.4

Exterior and Interior of the Calvaria.....•....••....•....• 8

4.4

1.5

Base of the Skull, External View ..•.....•....••....•.... 10

1.6

Base of the Skull, Internal View ..•.....•....••....•.... 12

1.7

Orbit: Bones and Openings for Neurovascular Structures .. 14

Cranial Nerves

Oculomotor (CN Ill), Trochlear (CN IV), and Abducent (CN VI) ............................... 72 Cranial Nerves: Trigeminal (CN V), Nuclei and Distribution. 74

4.5

1.8

Orbit and Neighboring Strucb.Jres •.....•....••....•.... 16

4.6

Cranial Nerves: Trigeminal (CN V), Divisions ••••••••••••• 76

1.9

Nose: Nasal Skeleton ......•....•..........•.....•.... 18

4, 7

Cranial Nerves: Facial (CN VII), Nuclei and Distribution •••• 78

1.1 0 Nose: Para nasal Sinuses....•....•..........•.....•.... 20

4.8

Cranial Nerves: Facial (CN VII), Branches••••••••••••••••• 80

1.11 Temporal Bone •..........•....•..........•.....•.... 22

4.9

Cranial Nerves: Vestlbulocochlear (CN VIII) •••••••••••••• 82

1.12 Sphenoid Bone •..........•....•..........•.....•.... 24

4.1 Cranial Nerves: Glossopharyngeal (CN IX) .••.•.••.•.••.• 84 4,11 Cranial Nerves: Vagus (CN X) .......................... 86 4,1 2 Cranial Nerves: Accessory (CN XI) and

1.13 Occipital Bone and Ethmoid Bones .....•....••....•.... 26 1.14 Hard Palate ...•..........•....•....•.....•.....•.... 28

o

Hypoglossal (CN XIII) .. , , , .. , , , , .. , , , .... , .... , , .. , , 88

1.15 Mandible and Hyoid Bone ..•....•..........•.....•.... 30 1.16 Temporomandibular joint..•....•..........•.....•.... 32

4.1 3 Neurovascular Pathways through the Base of the Skull,

1.17 Temporomandibular joint, Biomechanics ....••....•.... 34

Synopsis .......................................... 90

1.18 TheTeethlnslb.J ..........•....•..........•.....•.... 36 1.19 Permanent Teeth and the Dental Panoramic Tomogram ... 38 1.20 Individual Teeth ..........•....•..........•.....•.... 40 1.21 Deciduous Teeth .........•....•..........•.....•.... 42

2

Muscles ofthe Head

2.1

Muscles of Facial Expression, Overview ..•....••....•.... 44

2.2

Muscles of Facial Expression, Actions • • • •• • • • • • • • • • •• • • • 46

2.3

Muscles of Mastication, Overview and Supertlcial Muscles • 48

2.4

Muscles of Mastication, Deep Muscles • • •• • • • •• • • • • • • • • • 50

2.5

Muscles of the Head, Origins and Insertions • • •• • • • • • • • • • 52

5

Topographical Anatomy

5.1

Face: Nerves and Vessels .............................. 92

5.2 5.3

Head, Lateral View: Superficial Layer. • •.•. •• .•.• • .•.• • .• 94 Head, Lateral VIew: Middle and Deep Layers •• • • • •• • • • •• • 96

5.4

Infratemporal Fossa . . . .. . . . .. . . . . .. . . . .... . .... . . .. . . 98

5.5

Pterygopalatine Fossa . .. . . . .. . . . . .. . . . .... . .... . . .. . 100

6

Oral Cavity

6.1

Oral Cavity, Overview . .. . . . .. . . . . .. . . . .... . .... . . .. . 102

6.2

Tongue: Muscles and Mucosa .. . . . . .. . . . ......... . . .. . 104

3

Blood Vessels of the Head and Neck

6.3

Tongue: Neurovascular Structures and Lymphatic

3.1

Arteries of the Head, Overview and

6.4

Oral Floor. .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .... . . .. . 108

External Carotid Artery . . .. . . . .. . . . . .. . . . .... . . .. . . . . 54 External Canotid Artery: Anterior,

6.5

Oral Cavity: Pharynx and Tonsils . . . . .. ... .. ... .. . . . .. . 110

3.2

6.6

Salivary Glands .. .. ... .. ... .. . . . . .. . . . ........... .. . 112

Drainage .. . . . . .. . . . .. . . . .. . . . . .. . . . .. . . . .... . . .. . 106

Medial, and Posterior Branches . .. . . . .. . . . .... . . . .. . . . 56 3.3

External Canotid Artery: Terminal Branches • . • • • • . • . •• . • . 58

3.4

Internal Carotid Artery:

7

Nose

Branches to Extracerebral Strucb.Jres . •• . • . •••• . • . •• . • . 60

7.1

Nose, Overview ...... .. .......... .. ........ .. ...... 114

3.5

Veins of the Head and Neck: Superficial Veins •••• . • . •• . • . 62

3.6

Veins of the Head and Neck: Deep Veins • . • . •••• . • . •• . • . 64

7.2 7.3

Nasal Cavity: Neurovascular Supply• . • •.•. •• .•. •• .•. •• . 116 Nose and Paranasal Sinuses, Histology and Clinical Anatomy .... .. ... .. . . . . .. . ............. .. . 118

IX

Table ofContents

8

Eye and Orbit

10

8.1

Eye and Orbital Region ...•....•...........•....•.... 120

1 0.1 Coronal Sections, Anterior Orbital Margin

8.2

Eye: Lacrimal Apparatus ..•....•...........•....•.... 122

and Retrobulbar Space ............................. 1 56

8.3

Eyeball •.....•..........•....•....•........... • .... 124

10.2 Coronal Sections, Orbital Apex and Pituitary.........•.. 158

8.4

Eye: Lens and Cornea .....•....•................•.... 126

1 0.3 Transverse Sections, Orbits and Optic Nerve ............ 160

8.5

Eye: Iris and Ocular Chambers ..•.....•.....•....•.... 128

1 0.4 Transverse Sections, Sphenoid Sinus and Middle Nasal

8.6

Eye: Retina ...•..........•....•................•.... 130

8.7

Eye: Blood Supply ........•....•................•.... 132

8.8

Orbit: Extraocular Muscles ••••••••••••••••••••••••••• 134

Atlantoaxial ]oint .................................. 164

8.9 Orbit: Subdivisions and Neurovascular Structures ••••••• 136 8.10 Orbit: Topographical Anatomy........................ 138

1 0.6 Midsagittal Section, Nasal Septum and Medial Orbital Wall ...................................... 166

Sedlonal Anatomy of the Head

Concha .......................................... 162 1 0.5 Transverse Sections, Nasopharynx and Median

10.7 Sagittal Sections, Inner Third and Center of the Orbit .•.. 168

9

Ear and Vestibular Apparatus

9.1

Ear, Overview ...................................... 140

9.2

External Ear: Auricle, Auditory Canal, and

9.3

Tympanic Membrane .............................. 142 Middle Ear: Tympanic Cavity and Pharyngotympanlc Tube 144

9.4

Middle Ear: Auditory Osslcles and Tympanic Cavity •••••• 146

9.5

Inner Ear, Overview ................................. 148

9.6

Ear: Auditory Apparatus ............................. 150

9.7

Inner Ear: Vestibular Apparatus ....................... 152

9.8

Ear: Blood Supply ................................... 154

X

Table of Contents

Neuroanatomy

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

5

Diencephalon

5.1

Diencephalon, Overview and Development. . . . .. . . . .. . . 210

5.2 5.3 5.4 5.5 5.6 5. 7 5.8

Diencephalon, External Structure •• . • . • •. • . • • • • . • . •• . • 212 Diencephalon, Internal Structure . •• . • . • •. • . • • • • . • . •• . • 214 Thalamus: Thalamic Nuclei .. . . . .. . . . . .. . . . .. . . . . .. . . . 216 Thalamus: Projections of the Thalamic Nuclei • • • • . • . •• . • 218 Hypothalamus .. . . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . 220 Pituitary Gland (Hypophysis) . . . .. . . . . .. . . . .... . . .. . . . 222 Epithalamus and Subthalamus . . . .. . . . .. . . . .... . . . .. . . 224

6

Bralnstem

6.1 6.2

Brainstem, Organization and External Structure •• . • . •• . • 226 Brainstem: Cranial Nerve Nuclei, Red Nuclei, and

6.3 6.4 6.5 6.6

Substantia nigra. . . .. . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . 228 Brainstem: Reticular Formation • . •• . • . •• . • . •••• . • . •• . • 230 Brainstem: Descending and Ascending Tracts •••• . • . •• . • 232 Mesencephalon and Pons, Transverse Section•••• . • . •• . • 234 Medulla oblongata, Transverse Section •• . • . •••• . • . •• . • 236

7

Cerebellum

7.1 7.2 7.3 7.4

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

9.8

266 268 270 272 274 276

Descending Tracts of the Spinal Cord: Extrapyramidal and Autonomic Tracts.. . . . .. . . . . . .. . . . .. . . . .. . . . .. . 282

9.9

o Tracts of the Spinal Cord, Overview. . .. . . . .. . . . .. . . . .. . 284

9.1 9.11 9.12 9.13

Blood Vessels of the Spinal Cord: Arteries . • •. • . • •. • . • •. 286 Blood Vessels of the Spinal Cord: Veins .. . . .. . . . .. . . . .. . 288 Spinal Cord, Topography.. . . .. . . . . . .. . . . .. . . . .. . . . .. . 290

XI

Table ofContents

10

Sedlonal Anatomy of the Brain

12

FUndlonal Systems

10.1

Coronal Sections: I and II (Frontal) •.••.•.•.••.•.••.•. 292

12.1

Sensory System, Overview••.•.•.••.•.••.•.••.•.••.• 326

10.2

Coronal Sections: Ill and IV .•.••.•.••.•.•.••.•.••.•. 294

12.2

Sensory System: Stimulus Processing .•.••.•.••.•.••.• 328

10.3

Coronal Sections: V and VI. .•.••.•.••.•.•.••.•.••.•. 296

12.3

Sensory System: Lesions•.••.•.•.••.•.••.•.••.•.••.• 330

10.4

Coronal Sections: VII and VIII •.••.•.••.•.•.••.•.••.•. 298

12.4

Sensory System: Pain Conduction ••.•.••.•.••.•.••.• 332

10.5

Coronal Sections: IX and X •.•.••.•.••.•.•.••.•.••.•. 300

12.5

Sensory System: Pain Pathways In the Head and

10.6

Coronal Sections: XI and XII (Occipital) .•.•.••.•.••.•. 302

10.7

Transverse Sections: I and II (Cranial) ••••••••••••••••• 304

12.6

Motor System, Overview ........................... 336

10.8

Transverse Sections: Ill and IV ••••••••••••••••• • ••••• 306

12.7

Motor System: Pyramidal (Corticospinal) Tract •••••••• 338

10.9

Transverse Sections: V and VI (Caudal) ••••••••••••••• 308

12.8

Motor System: Motor Nuclei ........................ 340

10.10 Sagittal Sections: 1-111 (Lateral) ...................... 310

12.9

Motor System: Extrapyramidal Motor System and

Central Analgesic System •.•.•.••.•.••.•.••.•.••.• 334

10.11 Sagittal Sections: IV-VI ............................ 312

Lesions ......................................... 342

10.12 Sagittal Sections: VII and VIII (Medial) •.....•....•.... 314

12.1 0 Radicular Lesions: Sensory Deficits •....•..........•.. 344 12.11 Radicular Lesions: Motor Deficits •••••••••••••••••••• 346

11

Autonomic:: Nervous System

11.1

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

Connections .........•....•................•.... 320

12.16 Lesions of the Spinal Cord, Assessment .•..........•.. 356

11 .4

Autonomic Nervous System: Pain Conduction ....•.... 322

12.17 Visual System, Overview and Geniculate Part .......•.. 358

11 .5

Enteric Nervous System .•....•...........•....•.... 324

12.18 Visual System, Lesions and Nongeniculate Part •....•.. 360 12.19 Visual System: Reflexes....•.....•....•....•.....•.. 362 12.20 Visual System: Coordination of Eye Movement.•....•.. 364 12.21 Auditory System ...••....•.....•....•....•.....•.. 366 12.22 Vestibular System ..••....•.....•....•....•.....•.. 368 12.23 Gustatory System (Taste) ............ .. ............. 370 12.24 Olfactory System (Smell) ..• . .... • . . .. • . . .. • . . .. . • . . 372 12.2 5 Umble System • • . .. • • . ...• . .... • . . .. • . . .. • . . .. . • . . 374 12.26 Brain: Fiber Tracts .. • • . ...• . . . .. • . . .. • . . .. • . . .. . • . . 376 12.27 Brain: Functional Organization . .. • . . .. • . . .. . . . .. . • . . 378 12.28 Brain: Hemispheric Dominance . .. • . . .. • . . .. . . . .. . • . . 380 12.29 Brain: Clinical Findings . .. . • . . . .. • . . .. • . . .. • . . .. . • . . 382

XII

Table of Contents

Appendix

List of References Subject Index .................................... 387 .•.• • ••.•.••.• • ••.•.••.• • ••.•.•••• • •.••.• 389

XIII

Head Cranial Bones • ••••........•••• ••.....•• •••• ••.... 2 2

Muscles of the Head ........... ........ ..... .... 44

3

Blood Vessels of the Head and Neck . ••••••••••... 54

4

Cranial Nerves •••••••....•••• ....... •••••••••.. 66

5

Topographical Anatomy ...•••• ••..... • • •••••• ... 92

6

Oral Cavity .. .. ... .... .. ... ............ .... ... 102

7

Nose ......... ........ .. ... .............. ... .. 114

8

Eye and Orbit . . . ........... ........... . ....... 120

9

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 greygornotlc 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
Nasa!G!Mty

SlnlcluNt tMt .....

lntDthe--.. • Nasolaatmal duct

Mlddeoantha

mtl~Ws

Middle

meatus

SUpeflor

• • • •

fnlnulslnus Milldllarystnus Anterior ethmoid cells Mlddlt elhmold cells

•

~lforethmold aells

~~~Cj)l~m

tnfu'lor c~uha

mel!Ws Sphen~

elllmold reoess

• Sphenoid sinus

-

Ci O:IUomtatlll unttorttheleftskluftM Coror~al

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 frontMngthe 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 laterndla 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/ 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 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 <M!f the calvaria and Is loosely iltt3ched to the pel1osteum. The muscles of the calval1a that al1se fi'om !he galea aponeurotica are known colll!ctM!Iy as the "epicranial musde.• The two bellies of the ocdpltofi'ont;rlls (fi'ontal and octlplt;rl) can be clearly Identified. The temporop;~11ealls, whose posterior p;~rt Is called the iiU·

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 m!rlat - - - - - - - ; ethmoldal.artl!l'y

=---------:''"'\.;;;'---- 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 sheb!l')'gOid --"""":'':""""'i"\o~"'7"=--'l-'!l,iJ....-.'"""·•

plexus

~ltlrylll!!lns --------'"7-~----

•

lntlemal

Jugtlmoe'l'l

..,;~--------- Rdromand·

bulirYI!In

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

T011011111phkill origin

Name

Telenaphalon

• Olfactory nerve (CN I)

• Spees ~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<Jtion. Motor p~~ralysl5 Is accomp~~nled by dlstllrbances of sallwiiDn ind taste. Hypericusls due to p~~nlysls of the stapedius muscle has little clinical im portanee. Peripheral motor p~~ralysls Is .accompanied by dlstu rbances of taste and sallviUon. Periphe~l motor (fidil) parii)'$IS Is the only manifestation of a lesion Itthis level.

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

\

N.as.11glands

/

C~r--------------~11

petros;llnt!M!

Nucleus of t h e - -

~----------------~~~ Pllltfne

solttuytract

Qll'l!lllon

Gllr'l~ll.. bnr1d1es

SubmaAdlbuler ---~.._~"1 gland

c PlnJY~~~Pitflctk Wcm!l effm=n'blnd llf..:entl.tferents {gum tory ftbeft) ofthe hclill nl!f'ft

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
lntemll view,INse of the skull Anterior c:ranllol foua

• CriDrifonn plate

• Olfactory fibers (collected tD fonn CN I) • Anterior and posterior ethmoidal artery

Mickle Cl'lllnial fossa

• Optic canal

• Optic nerve (CN II) • Ophthalmic artery

• Superior orbital fissure

• • • • •

• foramen rotundum

• Maxillary nerve (CN V2 )

• Foramen ova&e•

• Mandibular nerve (CN V,)

• Foramen spinos!.X11

• Middle meningeal •rtery • Meningeal branch of CN v,

• Carotid canal

• Internal carotid artery • Carotid sympathetic plexus

• Hiollls of canal for greater petrosal nerve

• Greater petrosal nerve

• Hiallls of canal for li!S5er petrosal nerve

• Li!S5er petrosal nerve • Superior tympanic army

• Internal acoustic meatus

• • • •

Facial nerve (CN VII) Vestlbulocochlear nerve (CN VIII) Labyrinthine artery Labyrinthineveins

• jugular foramen

• • • • •

Superior bulb ofintemaljugularvetn Glossopharyngeal nerve (CN IX) Vagus nerve (CN X} Accessory nerve (CN XI) Posterior meningeal artery

• Hypoglossal canal

• Hypoglossal nerve (CN XII)

• Fora men magnum

• This foramen has an oval shape because it transmits the motor roots of the trigeminal nerve (CNV) for the muscles of mastication.

• Meninges

• • • • • • Extemal•spect, baseofthe*ul (where different from internal aspect)

Oculomotor nerve (CN Ill) Trochlear nt!rve (CN IV) Ophthalmic nerve (CN V1) Abducent nerve (CN VI) Superior ophthalmic vein

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.

Medulla oblongata, spinal cord Vertebral arteries Anterior spinal artery Posterior spinal arll!rles Accessory nerve (CN XI): entering spinal roots Spinal vern

• Incisive canal

• Nasopalatine nerve

• Greater p;~latine foramen

• Greater p;~latine nerve • Greater p;~latine artery

• Lesser palatine foramen

• Lesser palatine nerves • Lesser palatine arteries

• Foramen lac2rum

• Deep petrosal nerve • Greater petrosal nerve

• Petrotympanic fissure

• Chorda tympani • Anterior tympanic artery

• Stylomastoid foramen

• Facial nerve • stylomastoid artery

• Condylar canal

• Condylar emissary vein

• Mastoid foramen

• Emlssaryvetn

91

5.1

Face: Nerves and Vessels

This chapter describes the topogr.ilphlcal aBatomy of the anterior .ilnd l~teral aspemoftfle he;! d. It is ii$$Umed th.irttfle reilder iscdor port seep. 58 l'tf(ygoSd ptl1t: • Masseteric amry • Deep temporal arteries

• PWygoldbrand'tn • BIICCill artery

• Masseter muscle • Temporalls musde • rttrwold muscles • lluocill mucosa

~port:

D!Jedlan

lanlemg Jbuclure

• Post!rior supe~>ior al\lll!olar

Anterior

Maxillary tubenHity

amry • lnfraorbltll artery

l>cstleflor

Ptler}gold proc:JeSS Qaller.ll plate)

Medial

~endltularplate of the palatine bone

Lort.efal

- Lesser palatlnurt.ery

Communlc.1t.es with the Infratemporal fossa Ilia the pt:erygomaxillary fissure

Superior

Gremerwlngofthesphenoldbone,junctlon with the Inferior orbital fissure

Inferior

Op.ens Into the l'l!ti'Opharyngeal spa at

100

• Des«ndrng palatine artery - Gmb!r palatine artery • Sphenopalallne artery - lateral posterior nasal arteries

- Posttrlor septal brandies

• Maxillary molars. miXI11ary slnus, glnglva • Mulllary alveolae

• 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--"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
tllmor


brand!K,Im!'al pasllerlof nas.lla11!ffes

~~~~.....-- Oesarul-.gp.Ma11n~artl!ly,

g!Ntltr palatine nerve, and le:lut palatine neNes

lnflrlor nnal co nella

U\lula

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 Facilllll'tl!l')'

b

I.M.fa

E AntertDr and postertDr rfll-py

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 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
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, 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) 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$ue. The .aqueous fluid c;annot dr;aln Into the ;~nterior ch~mber ;~nd pushes portions of the iris upw.~rd, blodcing the chamber angle. • Chrw1ff or open'(lngk gloucomo (b), In wltlch the chamber angle ls open but dr;a!nage through the tr;abeoJiar meshwork Is Impaired (the red b.ar marks the location of each type of obstruction). By far the most common form (approximately 90% of all gl;aua~mas) Is primary chronic open-r nerw Postsynaptic ftbet$ from t~ superior ceNical ganglion Sensory tlbers from eyeball through ciliary ganglion to nasoc:lllary nene Passes Into cavernous sinus

• • • •

Oculomotor -,Inferior branch lnferlorophthalmlcvdn Infraorbital nerve Infraorbital amry

• • • •

Oculomotor nucleus In mesencephalon Passu Into ca~~emous sinus Branch of maxillary nerw (CN V,) Tenninal branch t:J maxillary arury (ext~mal ca~id artery)

Supra111Xhle~~r

al'tle'Y

Medial palpebral al'tle'Y SLCHWothlear vein

DorHI nnalveln

Anterior--~~-­

eltlmo!dai-'Y CEmnl _ ____,.,.,....._

retfrtal-ry Postlerfar et!lmo!dai-'Y

Optlc:neM lntl!mal

arotld-ry

Ophlhamic artery

Mkldle menlngealal'tlery

Ophlhamic "Win

An151omotfc blll'lth

C Brllnchas of oph'thllmtnrtery Right orbit. superior view ifter opening of the optk anal and orblt.11 rcof. The ophthalmic artery~ a branch of the Internal carotid artl!ry. It rum below the optic nerve ttl rough tne optic canal to the orbit and sup· pllu the lntraorblt.11 structures including the eyebill.

hferior

lntrnrbltel

ophthamitwln

win

fadalveln

D V.lnnf die orfllt Right orbit. lateral view with the lateral orbital Will removed ;md the

milldllary .slnw. opened. The veins af the orbit communicate wtth the veins of the wperfitial and dftl) facial reamey

Asaendtlg branch cJ supeildiJI petmal am.y

~~~i-

Desa!nd:ng lnnch cf supeilclll Pttn~AI~rtlery

Anllrfor Criii"OII.artltry

Bnnch~to

mpedlus (mpedal bn~nch)

Tensor tympani Stylom<JStllid ----'
Slruellft Ill the

_.,..nk.,...

snc&ul'l(s) ~ the ..ult ....~

CerttaiiCIUctuN

Paleopallium (oldest part)

Floor ofthe hemispheres

• Rhinencephalon (- alfadllry bulb plus surrounding region)

AIIOCDrtelc (see p.204)

Medial pcwtlon of hemispheric

o Ammon's horn O.argest part. not shown her.) • Indusium grlsalm • Fornbt

AIIOCDrte!c

• Neoconex(-conex),largestpartofthe ce.-,ral l!nlaoffon'bt

luddum Is a thin plite thit stretxheJ between the corpus callosum ilnd forniX, fosmlng the medial boundary of the lateral ventr1cles. Between the two ~ is a cavity of variable size, the aM/m npti pfllucidi. The d!ollnerglc nuclei In the septil, which are lnvoiYed In the organlziil:lon of memCHY, are connected to the hlppoampus bv the forniX (see p. 206).

Body arramlK

: . . ...~-------+--- W.ll'olll'llrlc:le. oa:lpltol ham

Crusof ----~--~--~~~~~~

fomlx

Cdumn

offon'bt

D Topognphyofthl hippocampus, famlx. iinll CJ1111USGI11511m VIewed frvm the upptr left iind Mal iiSpect. This drawing .shows the hippocampus on the floor of the lnfaior horn C1l the l--___;lpo';___ _ Lotl!rolwntrlde.

ll!mparll hom

miltter trut connectlng the hlppOCiimpus to the mammdlary bodies In the dlenaphiilon. C:OntalnedWithlnthefornlure hlppoamJNI neuRII'Is ~ illiDI!S project I:D the septum, mammdlary bodies. contralural hlppoamous, and other structure. This lmpomnt pathwiiy Is part of the Smbic.!ySiem (seep. 374).

205

4.5

Allocortex: Hippocampus and Amygdala

Corpus _ _T"'"".....,.=--':::~allosLm

~-f.....::'t-~~--::.--lh---

lndl.lllum g'lleilm

--~~~~~~~~~~--Rm~aM Nppoampus

Mammflary body

A left hJppoCimp.al l'annaUon L;atet;al view. Most of the left hemisphere hi!$ been ct~d ~.1_.­ lng onlytfu~ corpus c:.1llosum. fornix. and hlppoc:.1mpus. The lnt.1ct rfght

hemisphere lslllslble In the background. The hippocampal fDrmation is an important component of the limbic ')'$IW7I (seep. 374).1t consists of tnlft p;~rts: • Subit\llum($C!1C!Cb) • Hlppocimpus proper (Ammon's hom) • Dent.rte gyrus (fascia dent.tta}

I lllghthlppocamp;llforrmtfon andtheaud;rl partaftflefombl: IJ!ft: medial view. Comp;~ne this rnedlallllewofthe rfght hlppocamp;~l for· m.atiOnW!ththelatl!rallllewlnA.ilbove.AusefiJIIandmartc~theCAIIcartne

206

The tlber tract oftbe fornix connecu the hlppocamp!a to the mammlll;ary body. The hippoc:.1mpus integrates infol1niltion from various brain
C LefttemponiiDbewTdl the Wertor hom of the leten~lwntrtde apMed

• ll'anS¥8lle section, pom.rtar Ylew of the hlppoampus on the floor of the lnNrfor (tempor.l) hom. The following stl'\lctures can be ldtntlfted from lilteral Ill medial: hippocampus, fimbria. dentate QYfU$, hippoCiimpal sulcus, and p;anhlppoc.llmpal gyrus. b Coron~l sedlons of the left: hlppoCiimpus. The hippocampus appears here as a curled INnd (Ammon's hom • the hlppOCiimpus proper), whic:h shows considerable structural diVI!f51ty In Its different portions. The junction between the entorhinal cortex (entomlnal region) In tht pariihlppocampal gyrus Qnd Ammon's hom is formed by a tr1ns1Uonalarta, the subiculum. The entorhinal region Is the •gateway• to the hi~>­ poCimplll, through which the hippocampus re.:eilles most of its afferent fibers•

Lmrll nucleus

.. D lleladDIIIhlp afdlumvgd..l tD 'nbmll brilln ltnlduN Lateral view of the lllf't hemisphere. The amygdala (amygdaloid body) Is loated below the putamen and anterior to the tall ofthe uudm nucleus. The fibers of the pyramidal tract run posmrlor and medial to the amygdala.

E Alr'lyg&lll il

Coronalsectfon at the level of the lnte~n­ b1cu Ia r foramen. The amygda Ia extends medially to the Inferior surface of the cortex of the temporal lobe. For this reason, It Is considered to be part of the cortex as well as a nudear complex that has mlgntl!d Into the white mattEr. Stimulation of the amygdala In humans leads Ill changes In mood, nnglng from nge and rear to rest and relaatlon depending on the emotional state of the patient lmmedliltely prior to stimulation. Since the amygdala functions as iln "emotional amplifier; lesions ilffect the patient's evaluation of I!Y81I3' emotiOililf slgnlflunce. The su nou ndlng periiimygdallne cortex iincl the mrtfcomedl~ hiIfofthe amygdal• are put of the primary

11mmlssure

•

224

..

C Stnumn of the plnul gl.nd 1

Gross mlwgltblllssue section. b Hlstologlal section.

In llle gross tissue section, llle habenular commissure c.a n be identified at the oral end of the pineal. Below 1t Is the posterior (epl· !hiIa mlc) c:ommlssure. Between the two commlssures Is the CSFfilled piRNI retenofthe third V1:ntricle. C.lciflations (c:orpori aren· icell, •b111ln s~nd") are frequently present and may be vtslble on radiographs; they howe no pathological slg nlflcance. b The histological section demonstrates the specific cells oftbe pineal. the p/Molocytes, whkh 1 re embedded In a connective-tissue stroma and ire sunvunded by astrocyte~. The pinulocytes produce m~ fatonlll, which plays a role In the regulitlon of circadian lhythms; 1t may be blaen prophyladlully, for eta mple, to mod.me tbe effects of jet lag. If the plne~~l ceeelilr~

7

.4

Fadalnudeur. Cl!nlni~!!!Jne nbll

lr.ac:t

lll.tlra:tplnal

~.
A Artertes at tfle base of tfu~ linin The cen!bellum and tzmporallobe have been n!moved on the ll!ft side wdlspl;sythe courseohtte postErior cerebral artery. ThiJ 'Weww.as se· lecll!d because most ofthe arteries that supply the brain en!l!rtile cerebrum from Its basal .aspect. Note: the thr'ft principal ~rtzries of the cen!brum, the anterior, middle and poJ!I!rlor cerebr;ll ir!l!ries, 01rfse from different sources. The ante·

l1or and middle cerebral arterles .are branches of the Internal c.arotld artery, while the pc.sterior cen!bral arteries aretzrminal br.anches of the basller artery (see p. 246 f). The vertebral arteries, which fuse to form the b.astlar artery. distribute branches1»Ute spinal cord, brain stem•.arid

cerebellum (antelfor spinal artery, postzrtorsplnal.arterfes, superior cel'ebetlar artery, and anterior ~nd posterior inferior cerebetl~r arterin).

B Segmentr.lllfthe anterior, middle. and pod:l!ilior cel'l!bral artiKTes Segmentr.

Altl!ty

artsy

• Premmmunlallng part • Postcammunlcatlng part

• A1 • segment protdmal to the ant.ior cammunlcatlng artery • A2 • segment distal to the am.tlor communlatlng artery

Anterior untbral M'ocldle cerebral

• Sphenoidal p;1rt

• M I • firu hOd ---'.-~

thtlinmenmagnum (marginal sinus) "'--¥-~-~----

O<xlpltll tOnctyle

~-~---

ht2mol ).!gular win

£xt8T!alwrll!br.tl wnous plexus

--""""'1~----'t­

C Oc:dpltal emlaatyveh Emissary veins esubllsh a direct contleCtfor1 betweer1 the lntraaanlal dural sinuses and extracranial 111!in.s. They rur1 thrcUJgh small aanial openings such as the p;~r!etllillw"

nt.rnol anbr.~l ...n

-"•- - Me4ullilryvdn ~~4b~~~~~--~~-¥BnDfomrum semkMIIe

Supl!fftd.l midcl~ ardl111l ...n

T..mlnal wn Decpmldd~

loledlal•~or

«"'bnlwln

lent!tular'Wlhs

D Anlltomot" betwMn the superftclll ;md d"P mrebr1l veins Trans~e section thnlUgh the left hemisphere. anterior view. The superftdal cenebr;al wins communlate with ttle deet~ cerebril veins through the aniiiJtomoses ,J,-n here (see p. 260). F1ow reverSill (double 1rrows) rnayoa:urln the boundary:r.anes between two terrltDria.

259

Neuroai'H1tomy - - B. Blood Vessels offlu! Bl'tll1t

8.8

Veins of the Brainstem and Cerebellum: Deep Veins

A Deepa!n!bralvtl:nt Mult!planar tr~nm~rse section (CXlmblnlng multiple tr.mwel'5e planes) with a superior 11tew ofUte opened late!'ill ventricles. The tem· poral and occipital lobes and tentorium cerebeUI have been remOftd on Ute left side to demonstr~te Ute upper surfa~ of Ute cerebellum ilnd !he supelfor cerebellilr veins. On tne lateral Wills of tne anterior homs of both li!ter.!l ventrlclu. !he superior thalamostrlate vein runs tow.lrd the lnterventrlcular foramen In the grocM! between the thalam.a and c;~ud~te nucleus. After receiving tne anterior vein of Ute septum pelluddum and the superior choroidal vdn, It forms Ute Internal cerebral vein and passes Utrough Ute Interventricular foramen along the roof of the diencephalon tuward tne quadrigeminal plate. which CQn· talns the superior and Inferior CXlllla.tll. There It unites with the Internal cerebral vein of Ute opposite side, and the basal ~ns to fonm Ute posterlor venous confluen~. which gives rise to Ute great cerebral vein.

Anterfarw)l of - --':-- --'rl "PP:Um peluddum ~--~r--Supe~~lam~

strlateYI!In ~~~-_,~~~-~~--Supe~

choraldalv.!ln

~----:-:-- l.all!r 90% of cases. Much less commonly, cerebrlllischemlllis aused by lin obstructi~n of venoll$ outflow due 1:1> cerebral venous thrombinis (HIC!

264

Tlu"(lmbotlc~l inleft~m

8). A decrease of ar1:erial blood flow In the arotld system most commonly results trom .ilrl embolic or local tf!rombotlc occlusion. Most emboli origimte from Jtheromati>UJiuions at the c;~rotid bifurcation (arterioartErial emboli) «ti"om the eJCpulslon of thrombotic m;ater1al ti"om the left ventr1de {ardlac emboli). Blood does (tf!rombl} may be dislodged from the heart~ .a result of \'ilYUillrdlsease or .atrial flbrtlla11or1. This produces emboli that may be anied by the bloodstream 1:1> the brain. where they may cause U!e functional ocduslor1 of an artEry supplying tf1e brain. The most common ex.1mple of tf!ls Involves all of the dlstrtbutfon region of the middle cer1!1lralli1Ury, 'Wfllch Is .il direct continu;ation oftf!e internal arotid artl!ry.

NeuroamJtomy - - 8. Blood Vessels of the Brain

b

B Cerebral venous thrombosis Coronal section, anterior view. The cerebral ~ins, like the cerebral arter· ies, se~ specific territories (see pp. 258 and 260}. Though much less common than decreased arterial How, the obstruction of~nous outflow is an important potential cause of ischemia and infarction. With a thrombotic occlusion, for example, the quantity of blood and thus the venous pressure are increased in the tributary region of the occluded ~in. This causes a drop in the capillary pressure gradient, with an increased ex· travasation of Huid from the capillary bed into the brain tissue (edema}. There is a concomitant reduction of arterial inHow into the affEcted re· gion, depriving it of oxygen. The occlusion of specific cerebral ~ins (e.g., due to cerebral ~nous thrombosis} leads to brain infarctions at characteristic locations: a SUperior a!rebral Rlns: Thrombosis and Infarction In the areas drained by the:

An~rlor

cerebral artEry

t.lddle cerebral artEry

Hemlp.oresls (with or without hem!sensory delleIt}

Hemlp.oresls (with or without hemlsensory delleIt} mainly affecting

Bladder dysfunction

Aphasia

theiM1Tiand face(Wemlc~

Mann type)

Hem!sensory losses

Hemianopia

• Medial superior cerebral veins (right, symproms: contralateral lower limb weakness); • Posterior superior cerebral veins (left, symptoms: contralateral hemiparesis). Motor aphasia occurs if the infarction involves the motor speech center in the dominant hemisphere. b Inferior a!nebral veins: Thrombosis of the right Inferior cerebral veins leads to Infarction of the right temporal lobe (symptoms: sensory aphasia, contralateral hemianopia}. c Internal cerebral veins: Bilateral thrombosis leads to a symmetrical infarction affEcting the thalamus and basal ganglia. This is character· ized by a rapid deterioration of consciousness ranging to coma. Because the dural sinuses have extensive anastomoses, a limited occlusion affEcting part of a sinus often does not cause pronounced clinical symptoms, unlike the venous thromboses described here (seep. 256).

C Cardinal symptoms ofoc:clusion ofthethne• 11111ln cerebral arbl!rles (after Masuhr and Neumann} When the anterior, middle or posterior cerebral artl!ry becomes occluded, characteristic functional deficits occur in the oxygen-deprived brain areas supplied by the occluded vessel (see p. 250). In many cases the affEcted artery can be identified based on the associated neurological deficit: • Bladder weakness (cortical bladder center) and paralysis of the lower limb (hemiplegia with or without hemisensory deficit, predominantly affecting the leg) on the side opposite the occlusion (see motor and sensory homunculi, pp. 329 and 339) indicate an infarction in theter· ritory of the anterior cerebral arbl!ry. • Contralateral hemiplegia affEcting the arm and face more than the leg indicates an infarction in the territory of the middle cerebral artery. If the dominant hemisphere is affected, aphasia also occurs (the patient cannot name objects, for example}. • Visual disturbances affEcting the contralateral visual tleld (hemi· anopia) may signify an infarction in the territory of the posterior cerebral artery, because the structures supplied by this artery in· elude the visual cortex in the calcarine sulcus of the occipital lobe. If branches to the thalamus are also affected, the patient may also ex· hi bit a contralateral hemisensorydeficit because the affErent sensory fibers have already crossed below the thalamus. The extent of the Infarction depends partly on whether the occlusion Is proximal or distal. Generally a proximal occlusion will cause a much more extensive Infarction than a distal occlusion. MCA Infarctions are the most common because the middle cerebral artery Is essentially a dl· rect continuation of the Internal carotid artery.

265

Neurot1natomy - - .9. Spinal Cord

9.1

Spinal Cord, Segmental Organization

IIDDfplm

IIDDfplm

Alarpw Alor pllll!

Zoneuf

autonomic nourans

•

Zoned ai!Dnomk noui'IIIN

White-

....,plalll

Basal pllll!

---:1--t-- - Antlrtorhom

Floor plalll

R-pllll!

'--:::,..c..---- c.rtnl anol

Ill

A Dewlapment of the lpln1l Clll'd Transve~W sectiDn. wpalor view.

Eilr1y neural tube, lllntmnedlite sage, c: idult spinal cord. The spinal mrd dMclps from the neural tube:

il

• PDsteJtor hom: dewlaps from the posb!rlor part of the neural l.\lbe (the olor plate). It contains the afferent (senSOIY) neurons. • AntetTor hom; dev.!lops from the anterior P'rt Df the neur;~l t\Jbe (the bosol plcn). lt contains the efferent (motxlr) neurons. • Lillleriil calwnn: develops from tile lnll!rwnlng mne. Present only In the tharacic, lumbar, and sur,lregions of the mrd, it contains the autDnomk(sympathetfc and parasynnp;11thetk) neurons. (Its longltu· dlnal distribution Is shown In C, p. 283.)

~~~~~~--t--~~hom

c

Neurons dD not develop from the raDf or flDOr platu. Viewing the spinal cord In transverse section, we see that It mnslm of gray !Nitter that Is a rnnged about the central canal and Is surrounded by whim mollttl!r. The ti'IY JMtter contains the all bodies of neurons while the whb JMtter consists of nerve fibers (iiXDils). Note: alfOns that hive the samefunctlon are collected Into bundles ailed ttvds. Tracts that tl!rmlnate In the brain are called asandlng, o(ferent or at~SOI)' tracts, while tracts that pass from the brain int:D the spinal cord ~re c.alled descending, ~tor mof1Jr tram.

Spiral

Dorulroodets

Plglo

Merlngul branch

Splonchnk

n..-

_L_,

I 5trudure of ••ptn.l card Mgment

Two main organization~ I principles are observed in the spinal cord: 1. Fundfa1111l orglllll.lltiDII w1t~11 • .egmellt (viewed In .a transverse section Df the spinal mrd). In each spinal cord segment. the cr/fetmt dors~l rootlets enter the back of the cord while the t/ffmrt -vartro1l rootlets emerge from the front of the cord. The rooCfets In each set mm brne to form the dorsal (posUrlor) and ventral (anterior) roots. Each dors~land venlnll raDt fuM:s to form a mixed ,mcrc-·which carries both sensory 1 nd motor fl~. Shortly after the fusion of Its two raats, the spiN I nerve diVIdes Into vartous branches. 2. TapagraphiiCII arpnlulbl of the ugmenb (viewed in a longitudinal sediDn of the spiN Icord). The spiN Icord consists of a wrtlcal sertes of31 segments (2eC), e.~d't ofwhld't lnnerwtes a speclflcarea In the trunk ;md limbs.

C Splnll card 11nd tpl1111l ,.IIIII• In 111tu Postufor view with the lam lm1r ard'tes of the vertebral bodies removed.

The longltudiNI growtn of the spinal cord lags behind that of the bony vertzbral column. As a result, the l~r end of the spinal mnd In the ~dult lies at app~U~rtkD-

•plnaltract

----+-:---- Rub""f'lnalandtract ~cuiDSplnal

A T'rKtl of the Gt1'8J¥11mldll mlllllr system In tfle 1p111111 CDrcl See p. 285 for owrvlew f1f descending tracts. Unll~ the pyramidal tnoct, which controls conscious. voluntary motDr activities (e.g .. rals· lng a cup to the mouth), tile e.wttllpyramlclill motDr system (cerebel· lum, bas;~ I gangli01, and motDr nucl~i of the brain~m) is ne~Hry for ootomolk and lmmrd motDr pro~ses (e.g.• walkfng. running, cydlng). The division Into a pyramidal ilnd extrapyramidal system has pnoYen useful In cllnlal practice. A recent .alternatlw daulflcatfon dl· vides th~r descending tncts into a liiteriil il nd m~iil system. Und~r tills duslflatfon. the lama/ ~lrm lndud~ • Lltl!ral cortlcosplnill tract(- pyramldil trilct, seep. 280) • Rubrospinal tnct (extrapyramidal)

The lateral system projects predominantly to the distal muscles, particularly those afthe upper lim b. and th1.11 critically influences flne, discriminating motDr functions of the hand and urn. The ~lui symm projects millnly to the neurons of the trunk .;md lower limb musdes and Is thus concerned with the motor aspects of trunk posJUon and stance. The media/.I)'S!MI consists of three exlr.lpyramidal tracts: • Anterior retlculosplnal trut • Laterill vestfbulosplnil trilct • Tectospl naltnct The centrilf connections of this system are lflustril~ In I . Because the pyril mIdill ilnd u.tnpyramldal tracts are dosely lnt«aannected and run close to one other, lesions generally affect bath tract systems simultaneously (see p.343). Isolated lesions of either the pyramidal or e~~trapyramldal path wily ill: the spina I cord 1~1 are virtually unknown.

282

tid>'.,..,.......... c•·

I Clftlnl DffQIIUnd CIIUne afthe Delilnlund Gehlen) The nude! of oltgln of the extro~pyDmld~

tr
unt In the regula!lor1 of sexual behavior). While the plane In A passed through the .ilnterfor comml55ure, this more occipital plane slices the mammillary btldies (see E). Pathological changes in lfle mammntary bodin can be found during autopsy ofchronk alcoholics. The mammll· lary bodies are flanked on each side by the foot o{thf hfppoalmpus. An Important p.art of the Umble systl!m, the mammillary bodies are con-

nected to lfle hippocampus by the {omlx (see F). Due to the anatomical curvature ofthefornlx,lts cofiJmn Is visible lr1 more fro nul sections (see A), while ItS cruro .ilppear as Widely sep.;~rated structures In more occlplul sections (see c. p. 299). The septltm ~lucidum stretches betwl!en the fomlx and corpus callosum. fomnlng the medial boundary of the later.ill ventricles (see A and D). The first stJuctlJre of the brainstem, lfle pons. can also be identified in this section.

Corpus callosum.

trunk

Lumen of thlrdwn!Jid~

Fomlx.

coklmn

E MldAgllial sedfon through the diencephalon ;md bl'illnstem

F Mlmmlll;uybodtes;mdfomlx

l..lteril view.

295

Neuroai'H1tomy - - 10. S«ttonGIAnatomyaft:ltdraJn

10.3 Coronal Sections: V and VI

Plltlmen

Em!mal apnfe

Glob~apalrdus, --+=:::t::_::~~-.;..---­ lat!er.alsegment

lmt111 wntride, ten-coon~l i'lom

Fmblfa of N'ppocampus HpPoc:amp~s

A CoronilhldlonV The appearance of the central nuclear region has changed marlcedly. The caudatl! nucleus Is cut tvllce by the plane of this section. Its body bord~ the central partofthelatC!r.!lventride.~nd a sm.allp~rtionofits ~il borders the Inferior hom ofthewntrfcle(seeCand E). 8eau5ethehe:ad and body of the caudate nucleus rlm the lateral aspect of the anterior (frontal) horn and the C!ntral part of the lateral ventride, the caudate nucleus has a curved shape slmllarw that of the ventricular system (see C}. Thus, the tall of the caudate nudeus Is ventral and liltefillln relation to Its head and body. Paflel E shows that a coronal 5eetlon through Ute tail of the Cludate nudeus cuts the oa:ipi~l portions of the pull:lmen. A section In a slightly more ocdpltal plane may not contain any part of the basal ganglia at ~toryCIDita.

a Amplitude of the neuronal response In the primary somat»sensory cortex to a pe!1phml pressure stfmulus. The Intensity or the stimulus Is shown in b. The d-.agrams illustrate the principle of sensory information processing In the cortex. Whmapprwdmatdy100 Intensity detectors In the fingertip are stimulated by pressure. appradmatdy 10,000 neurons tn the corresponding cell column In the primary somatosensory cortex (see columnar organimion of the cortv. p. 201) fl!.IP~d to the stimulus. Because the Intensity ofthe peripheral pressure stimulus Is moudmal at the center ind fides toward the edges, It Is processed In the cortex ~ccollllngly. cartkal processing amplllles the contrast between the gruter and lesser stimulus int!!ns'oties, resulting in a sharper peak (a). While the stimulated a~ on the fingertip measures appmxlmately 100 mm2, the Information Is processed In only a 1-mml irei of the primary somatosensory cortex.

329

NeurDGnatomy - - 12. FunctlontJI Systems

12.3

Sensory System: Lesions

A Sites of occurrence of lesions In the sensory patllways (after B~hr and Frotscher) The central portions of the sensory pathways may be damaged at various sites from the spinal root to the somatosensory cortex as a result of trauma, tumor mass effect, hemorrhage, or infarction. The signs and symptoms are helpful in determining the location of the lesion. This unit deals strictly with lesions in conscious pathways.The innervation of the trunk and limbs is mediated by the spinal nerves. The innervation of the head is mediated by the trigeminal nerve, which has its own nuclei (see below). Cortical or subcortical lesion (1, 2): A lesion at this level is manifested by paresthesia (tingling) and numbness in the corresponding regions of the trunk and limbs on theopposireside of the body. The symptoms may be most pronounced distally because of the large receptive fields on the fingers and the relatively small receptive fields on the trunk (see previous unit). The motor and sensory cortex are closely interlinked because fibers in the sensory tracts from the thalamus also terminate in the motor cortex. and because the cortical areas are adjacent (pre- and postcentral gyrus). SubtiNIIamlc lesion (3): All sensation is abolished in the contmlaterol half of the body (thalamus - "gateway to consciousness"). A partial lesion that spares the pain and temperature pathways (4) is characterized by hypesthesia (decreased tactile sensation) on the controla!Erul face and body. Pain and temperature sensation are unaffected. Lesion of the trigeminal lemniscus and lateral splnotiNIIamlc tract (5): Damage to these pathways in the brainstem causes a loss of pain and temperature sensation in the contrala!J!rolhalfoftheface and body. Other sensory qualities are unaffected. Lesion of tile medial lemniscus and anterior spinothalamic tract (fi): All sensory qualities on the opposit!? side of the body are abolished except for pain and temperature. The medial lemniscus transmits the axons of the second neurons of the anterior spinothalamic tract and both tracts ofthe posterior funiculus.

330

Lesion of the trigeminal nucleus. spinal tract of the trigeminal nerve, and lateral splnotiNIIamlc tract (7): Pain and temperature sensation are abolished on the ipsilateral side of the face (uncrossed axons of the first neuron in the trigeminal ganglion) and on the contmla!J!rol side of the body (axons of the crossed second neuron in the lateral spinothalamic tract). Lesion of tile p01terlorfunlwl1 (8): This lesion causes an ipsilateral loss of position sense, vibration sense, and two-point discrimination. Because coordinated motor function relies on sensory input that operates in a feedback loop, the lack of sensory input leads to ipsilateral sensory ataxia. Posterior hom lesion (9): Acircumscribed lesion involving one or a few segments causes an ipsilateral loss of pain and temperature sensation in the affected segment(s), because pain and temperature sensation are relayed to the second neuron within the posterior horn. Other sensory qualities including crude touch are transmitted in the posterior funicu· Ius and relayed in the dorsal column nuclei; hence they are unaffected. The effects of a posterior horn lesion are called a "dissociated sensory deficit." Dorsal root lesion (10): This lesion causes ipsilateral, radicular sensory disturbances that may range from pain in the corresponding derma· tome to a complete loss of sensation. Concomitant involvement of the ventral root leads to segmental weakness. This clinical situation may be caused by a herniated intervertebral disk (seep. 345). lesions of unconscious cerebellar tracts that lead to sensorimotor deficits are not considered here. The volume on General Anatomy and Musrulosla!/etal S_vsWn may be consulted for information on peripheral sensory nerve lesions.

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

KM+-- - - - - - - - Sphallemnll:l:us

(~nterlot.,dlatml

lpir>Othalolmk ~Cl)

1----Tlfgemln.ll lemnlsclls

-H-- - - - Lat!el'liiSII(r!Otflllamlc~ct

- -+- - - : ----i TI"+-1'--- -.;....--

Print~l (pont!M) nude~ad trlgem'mi~WM

-+":"-'=-- - - Spl~lnudeusol trlgemilll nenoe

Lat!e!'lllsplr!O-

- --1

!----+- - Tr.u:tsol

posteriorlunlt\llus

thalilmlt ll'act

10

331

Neuroai'H1tomy - - 12. Functional S}tmms

12.4 Sensory System: Pain Condudion

I

~~

....

41

II

II

51dn

I

Plnplldc.

prusure

o.ppalll

fr

II

N..-..,.lldc pain

fr

ConneciM tlllue. musda. bana.Jalnll

NIIWI, IIIIWtllsUe

MusdeJPUm, heamdle

N
334

The axons of tile second ne~mms cross the midline and travel In the trtgemlnaChal.ilmlc tr.ilcttothe ventral posteromedial nucleus and to the inlr.llaminarthalamicnuclei on the opposite side. where they terminate. The third (thalamic) n~ron of the p.aln pathway ends In tile prfrn.ilry somatosensory cortex. Only the p.aln flbers of the trigeminal nel"'e .ilrt' pictured In the dlillgram.ln the trtgemln.ill nel"'e Itself, tile othefsensory fibers run p;~rallel to the p.ain fibers bvt terminate in various trigeminal nuclei (seep. 74).

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

B ~ ofd!.e antnldeSO!I'Idlng

-lgetTcsyltl!m (after Lorlce) Besides !he ascending pathways tililt tallY pain sensation to the primary somatosensory corte., there ~re ~lso destl!nding pathways thathavelheabilltyto5Uppresspaln lmpcJisu. Thecenttal relilystatlonforthedescendlngan~lgeslc (paln-relrev!ng) system Is the central gr~ matter of the muencephalon. It is actiYo~ted by afferent lnpcJt from the hypothalotm~JS, the prefrontal cori2X, ;mel the ;unygelotlold bodies (p.art of the Umble system, not shcwn).ltalso reaiveul!i!rentinput from the spinal cord (~ep.333). The axons from the excitatory glutamlnerglc neurons (red) of the central gr~ matter terminate on serotonlnt!'gic neurons in the raphe nuclei and on nora~ renergk neurons In the locus ceruleus (both shewn In blue). The ax.ons from both types of neuron de.scend In the posterolaterlll funla; Ius. They tenninate directly or indirectly (via Inhibitory neur01u) on the analgesic projection naJrons (second afferent neuron of the pain p;athw..y), thereby Inhibiting the further conduction of pain impulses.

W "¥t- - - - Anteior

prettvide the cortical representitlon gfsp;~ce.which Is lmportint In precision gqsplng mowments and eye movements.

Supplomonlllry

mo!DrCOI'ID Preantralgyrus

\

(prtmory mllllr - - - - - - - . \ cortn.Ml) . ~ I' Pn!mabr

cortn

-----c-.,.---

Centnil lOllall

I

f /

PostanlniiD'US

. / (p~lllllrysomatosensorymrtooc)

c

CDnnecflonl Clfdle mrta:Widlthe lasal glft!llll lnd cereellum: P"'tnmml111 mmpla...-mlnb

I

l'lllldum

The pyrimldll motln 'ystem (the prfmarymoIDr cortex 1nd the pyrimldi Itract 1rlslng from it) i5 apirted by the INS.JI ganglia and cerebel1urn In the pl1n nlng 1nd programming of camplex mCM!menl:s. While illfterent fibers af the motnr nuclei (g.-,) pR!Ject directly ID the biiSal ganglia (left) without syn;1 psing, the arebellum Is Indirectly controlled via pontine nuclei (rtght; seec;. p.2l3). The moan thalamLJS piVIIIdes a feedbick loop for both structures (seep.341). The effetl!!nt fibers of the biiSal nuclei and cerebellum are distributed to lowl!r structures lndudlng the spinal mrd. The lm porta nee af the baul g~ngl~ and cerebellum in voluntary lnCIV8Tients can be apprec:tited by noting die ~IS af lesionJ In these structures. While disuses of the biul ganglli Impair the lnltlatlan and I!XI!cutlon af m~ mlflts (e.g., in Parldnson's disease), ~bellir lesloru are ch1ncterlzed by unmordlnated writhing lllCNaTlents (e~ .• the reeling mowments of lnlbr~tlon. a used by a tempon ry txWc insult to thto ~bellum).

I

I

c..b,.lmrtlol

I

1 L1 1 1 I Thollmus

I

I

9

c...!MIIam

I

1

-1 71

I

1

Splnol CD'd

t

I

L__-... _-_ ...._-_ ___.I-LI_SIIolml_,.,_ldiDI_rnotDr_. _

_J

D Simplified lllodl dliiQnrm Ill die sellllllfmalortyltl!m In m-ment contra! Volu nblry movements require constint feecl-

back from the periphery (muscle .spindles, tA!ndon organs) in order 1:4 remain within the desired limits. Because die motor and sensory systenu are so dosely ln!z!Telited functionally, they o11re often described Jointly .n the sensorimotor system. The spinal cord, brainstem, cerebellum, and cenebnl cortex are die three control level' af the sensorimotor sy5tem. All lnformoiltlon from plflphery, cerebellum, and the bisal ganglia passe through the thai:! mus on Its MY to thto cerebral cortex. The din leal lm portance af tht- sensory SY'~ In movement Is lllustnted by the sensory 1tD11 that may oa:ur when sensory functian is lost (see D. p. 353). The oculomotor camponent of the sensorfm.otnr system. Is not shcMn.

337

12.7

Motor System: Pyramidal (Corticospinal) Tract

Nm~~i~~ Pylamldal

faao--..,....-'

A Caui'JII! Ill the ,nmld•l (mrUmspllnll) 1nct The pyr;~mida Itract consists of three fiber systems: corticospinal fibers, cortlconudear fibers, and cortlc:oretlcular fibers (the l~r ire not shown here; they pass to the glgantocell ular nudeus of the reticular fvnmtion in the brainstem and will not be diSCU$Sed further). These groups of fibers constltub! the descending motor pathways from the primary motor cortex. The corticospinal ftbers piSS to the motor anterior horn cells In the spinal cord, wh lie the cortlcon udear fibers piSS to the motor nuclei ofthe Cl'1 nlal nerves. COrtlcolpTn•l fllen: Only a SINII percentage of the i!XOns of the corticospinal fibers ortglnate from the large pyramidal neurons In lamina V of the precantral gyrus (the laminar structure Ill the motor cortex Is shown In D). Most of the iXIIIIS irlse from sm;lll pyramidal cells and other neurons In Ia mlnae V and VI. Other IXOOS ortglnite from ad)ilcent brain regians. All ofthtrn detand through the intl!!rnal capsule. Eighty percent ofthe fibers cross ~ ntldJIM It the level of the medulla oblongata (decuSSitfan of the pyramids) and descend In the spinal cord as the /crtmJI CDttitvtrpinQI (pyromidr;rl) trclrt. The IHIC106sed fibers descend In the coni iS the ontMo!' cortlco!plna/ (pyramidal) ttoct and aoss liter •thesegmental I-I. Mast of the amnstl!rmlnlll! an lntercalatl!d cells whose synapses end on motDr n~uvns.

338

}

trxt

Nob!: the biiSic patb!rn of sami!Otaplc orvanlzitlon described earlier at the spinal cord level is found at all level$ of the pyramidal tract. This ficllrtates IDCi!lrmlon of the lesion In the pyramidal tract. COrlkDnuclelr fibers: The motor nuclei and motor segments of the cranial nerves receiw their iiXDns from pyramidal cells in the facial region of the premotor corm. These cortlconudearflben terminate In the contralateral motor nuclei of cranial neiWS Ill-VII and IX-XII In the br.~lnstem (the fibers to other br.~lnrtem nude! are shown In C). Besides this contrillateral supply, illCDns also pus to several cranial nerve nude/ on the $;!me (ipsilateral) side, resulting In a bilatetal innervation pattern (not shown ha-e). lhls dual supply Is clinically lmpoltmt In lesions of the frontal brand! afthe fadal nerw, for eumple (seeD, p.. 79). Notes on the • pyramida I tract": Some authors interpret this tl!rm as i!pplylng sb1ctly to the porUon ofthe tract below the decussation Illthe pyramids, while other authors apply the term to the entire tract. Most publlcatlons,lndudln9 this •das. use "pyramidal trict" as • collectl¥e term for all of the ftber tracts desafbed here. Some authors derive the term not nvm the deWSo1ation of the pyr;om ids but from the giant pyramidal cells (IIetz cells) In the cerebral ortu (seeD and p. 211 ).

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

B

Som.ltatoplc~nofthetb!fetalmlllde

In the pn:ccntnl !jyruJ (motor homunc:UuJ)

Anterlor111ew. Regions In ~lch the muscles areverydenselylnnesvated {e.g., the hand) must be supplied by many neurons In the precentral gyrus. As. a result, they rt<juire a largerrepresentation area in the corta than regions supplied by fev.w n~rons (e.g., the trunk). This cortical representation Is analogous tD that In sensory lnnervatfon, where areas af varying size are also represented In the a:ortex (postcentral gyrus; compare with the - r y homunculus in C. p. 329). One cortical area Is devoted tD the trunk and limbs and another tD the head. The -

'Pinaltract

- - - --++--1

~lwstbulo>. ------,#----14~

spiNIITKt

_ _ _ _ _ _ blla.llooplnol

tract

ftber(1a)

r-~~~-~--~--lmemwmn

Colglfbef(1b)

-.......!'--------=:=.....-- Alpha motor ntuiCII ca1Fber

yFlber

A De~eendln1 tram lilt the extnpynmld1l matar sptem The neurons of origin of the desanding tr.lc:ts of the exlr.'l!¥ilmidal motor system • 1rtse from 1 hellerogeneous group of nudeIthat lndudes the basal ganglia(pubmll't, globus pallldus, and cauclab! mx:leus), the red nucleus. the substilntt1 nlgn, 1nd mm mutur cortiCII areas (e.g., area6). The following desa111dlng trlc:ts arlt put of thlt extraP'J'ramldal motDr sysb!m:

• Ru bro:spinal t"ct Ollvosplnal met Vltstlbu losplnlll tract Rettculosplnal met Tectospinal trlct

These long desandtng tnc:ts Um11na on lnterneurons whkll th111 farm synapJQ vnto alphl and gamma motor ne\Jnii!S. which they con-

342

!:---+ ---:------ '!Kto6pll\lltratt ~~...,_

Anr.~llllpnl --~'/

• • • •

1-- - - - - - tplnalll'oltt Antlrtorcortla>-

trol. Besides these long d~cendlng momr tr1cts, the motDr neurons additionally rta'ive S$1sory input (blue). All impulses in these pathwilys are Integrated by the at phi motor neuron and modulatE lb ldlvlty, thereby affecting muscularcontracUans. Th1 functional Integrityoftile alpha motor neuron Is tested cllnlc111y by reflex testing. • TheWml "extr.lpyramidal motln system• has bee! critidzed ~ause Its functlonil and inatl:lmiCII components 1re so closely llnlced to the pyramidal motor system that the dlstlncuon seems arbitrary In an anitomle~l sense-p~rticular1y since the sysllem does not lndude cerebellar tnc:ts that ill'l also lnvolwd In the control of motor function.

Neuruanatvmy -

12. FunctlonaiSysmns

Leg

~ Tru'* -

--r- - Arm

Pynmlclll }

t iXI

•

~)

Pyromldll tract

I Lesions afthe mnlnll rnatDr ..,._.and thelrefhds

ducent nucleus may ause lpslllbnl d1m1ge to the trtgemlnal nudeus

LefTon'*' the c:or11tll (1): paralysis of the musdes inn~ by the

(not $hown).

damilged cortlal iln!l . Beause tbe face and hind iln! represented by partlculilr1y l1rge iii'HS In the motDr cortft (see I, p. 339), par.1lysls often affects priiTiirily thun11 and face ("brachiofacial" paralysis). The parillysls lrm rtibly ilffects the side opposltl! the lesion (decussation of the ~mlds) and Is flaccid and partbl (pareslsJ r.ather than compll!!b! beause the extrapynmldil fibers are not daiTiiged. If the emapyramldal fibers were also damaged, the result would be complete spastic pcrttJI)$is (see below). Lesion at the lew! of the lnlilmll capsule (l): This leads to chronic. contralateral, spastic hemiplegia (• complete pariiilysls) beause the lesion affecb both the pynmidil tnlc:t ;md tbe extr--- ---=--=-- - - - Ant2flor cutanecw;

br.lndlK

D lbdlcuillrlnnerwtlonoftfletrunk The scgment.11 arr.-angement of the musculature Is preserYed In the trunk. and so ttte ttunk ret.11ns a segmental (radicular) Innervation pilttl!m. Because the nerves In ttte trunk do not form plexuses, the radiou~r innervation patb!rn continues into the peripheral territDry of a artaneous nerve (T2- T12: see B). It un be seen that afferent flbers from the sympa1hetlc ttunk reach the peripheral nerves distal to the roots. This explains whyradlou~r lesions .are usually not associated Mth autl:lnomic deficits in the affected clermatomu. E Pftssure on spinal nl!nle I'OCitl from 1 hemlltied lumbar dTikofL4/5 A herniated Intervertebral disk may exert pressure on the spinal nerve root or cauda equlna. The disk consists of a antral gelatinous core (nucleus pulposus) and a peripheral ring of fibtoc;'lrti~ge (anulus fibrosus). When the anulus flbmi~JS Is damaged, mmrial from the gelatinous core may be extruded through the ring defect and Impinge upon the root it Its entry Into the lntervenebril for.1men. This Is,. frequent cause of radicular symptoms, whkh 1\ave two gr.aclel of sewr!ty: • Irritation of the nerve root In the region of the Intervertebral fora. men. This leads to pain in the lcwback(lumbago), potentiallyaca:un· panled by pain radiating Into lfle lower limb In the dermatone of the .affecll!d root (sclatka). • Alarge disk he!"nlatlon may compress the dors.alandtorventral spln.al nerve root. causing- pain in addition to $C!I\SOfY deflcib and (if lfle ventral root Is affected) motor deflctt:s.

LS wrtl!bral body

;a PosteroiiWr;~l disk heml;rllon it the L4/S level. This damages the

LS root passing behind the herniated disk but not the descending L4 root. which has already entered the lntefvertl!llral foramen it !hat level. As a ~lt. the sensory deficits are maniti!sted in the LS dermatome (see 1). Only a far ~ter.rl disk llernlatfon will damage lfle root !hat exits itthe same lewl as the affected disk. b Postl!fomedlll dllkhemllltlon itthe L4/51evel. The material hemlatzs through the postl!!riarlongitudin.alligament and impinges on the cauda equlna. Cauda eqvltl matte!' In the otherwise gray cerebral cortex (tile stria of GenBari, see c). Thh1/lhlt:e stripe runs parallel to the brain sul'faa and Is shclwn in the inset. where the gr;ay matn!r of the visual cortex is shaded light red.

• First neuron: photoreceptor rods and canes. loc.rted on the deep

relfnal surt.lce opposite to the direction of tile Incoming light ("In· version of the retina"). • Secvnd neuron: bipolar cells. • Third neuron: ganglion cells whose axans are collected to fonn tile OptiCnel'l/e. Optic n - . optk ellJan, and optic trlld:: This neural portion of tile wual pathway Is part of the centrlll nei'I/Ous system (optic nerve • tr.~nial nel'l/e II) and issuJTOunded by meninges. Thus. theopticn- is actually a tract rather than a true nel'l/e. The aptfc nerves join bdowthe base of the diencephalon to fonn tile optic chiasm. which til en d!llfdes Into the tv..o oplfc tracts. Each of tllese trllcts dlllldes In IIJrn Into a lat· eral and medi;!l root.

,....

---=~-

D D

L8't hllf of 'flsuallleld

RJQht ~~;~Ifof~~tw;~llleld

Ni5ilvl!iuillleld ofr!Qhteye

- - Ten'9flr.ll~sualfleld of light~

I Rapr-.entil\lon of Nch vtaal flllld tn the CDnt.r.llater.irl 'WtsuaiCDrtu Superior lltew. The light rays In tile nasal part of each \llsulll field are projected t» the tMipOI!ll half of the retina. while those from the tern· poral part;rre projected to tile retln;rl h;rlf. Bec;r~&Se ofthis ;rrrangement. tile left half of the wual tleld pro}ects to tile visual cortex of the rtght «cipital pole, and the right half projects to the visLI:!I mrtex of tile left «dpltal pole. For darlty, each visual tleld In the diagram Is dllllded Into two halves. and the re;rder should understlnd tills basic dMslon before we explore how tile lllsual fields are diYlded Into four quadrants (C). NoU!: The axanal fibers frDm the natal half of each retina cross to tile apposite slde it the optic chiasm and lflen triVt'l with tile uncrossed flbersfromthetemporal half of each reUna.

358

6""-~-+--

Lmral

genlalm body

Nf!uiOGDGtomy - - 12. f'undiomliiSymms

Maallr >lsual field

D lnformahfsval 1\'eld exo~mlntlfon with the confrorltlltTon test Th~ visual field t:!Xllmination is an essential step In the ex.amlnatfon ofleslons of the llfsual pathWliY (seeA.p.360). The confrontltlon test Is ;m fn(onnoltert rn which the examiner (with an intact visual fteld) and the patient sit face-toface, cover one eye. and each fbces their gaze on the other's open eye. aeatlng ldentfca1111sual axes. TheexamlnerthenmCM!S hlsorherlndex linger fn:Nn the outer edge of the visual fM!Id toward the cenwr until the patient signals that he or she can see the finger. With this test the ex- --.;..?-----:~!.'\, nudar film I

_AL:~---=--- Un!b...

'-

....,duct

\Jo-.!lb - - - - - - - Meclll langltudlnol folliculus

t:o111cospml -.....;;....--\ b'.a

4!,.-..:....-_..;..._ _ _ Nudeusaf abdl.ant""""'

I CouiH Gf tile medllllongltudl111l f..cta.~lusln the bl'llnstem MldAgltt.l J«tton viewed from the left side.

The medial longltlJdlnal f.udculus runs antzrior to the cerebral aqueduct on both sides and con1fnues from the mesencephalon to the cervical spinal cord. It tn nsmlts ftbers for the coordination of conjugate eye mCMments. A lesion of lfle MLF results In lntzrnuclear ophth.almoplegla (see C).

C ._lon of the mtdlallonglllldlnal faldcUUIII'IIflrltamudHrophth81· maples~II

-.....cl•

.........,h.ll

~­

ebd. . . . . . . . . .UI)

• Anlllnorvlew

Right

~

!

Medill A!c1la - - - . ; . . . . (not •
fadal nucltus

kes the stapedius reflex ;md the tympanic mernbr;me stiffens. The change In !he resistance of the tympanic mernbr;me Is !hen mei!ISured .md recorded. The aflierent trmb of !his reflex Is In the cochlear nerve. Information is co~d to the facial nucleus on each side byway of the superior olhr.sry nucleus. The f(ffmlt limb of this reflex Is formed by special visceromotor fibers of!he facial nerve.

Inner hair all

Liltler.ol cllllccodllea r bundle

' .i -----I

c Efferent Abers from the olhe till the Corti org~~n Besides tile ilfferentflbers from the organ of Corti (see A. shown here In blue), which form !he vestlbulocochlear nerve, !hen ire also efferent fibers (red) that pass to !he organ of Corti In !he lnntf ear and are conarnedwith the active preprocessing ofsound (•axhlearamplifier"}and acoustic protection. The efferent fibers arise from neurons thit are to· t.'!ted lr1 elttterthe lateral or medial part of!he superforoiiYe ind project &om there to the cochlea (lateral or medial otrvocochlear bundle). The

ltl,lf,

fibers of !he lateral neuron$ p;~~s uncros.ml to the dendrites of the irtnu hair cells, whlle the flbers of the medial neuron$ cross to the opposite side ind terminate at!he bise of!he ouf1!r hair cells, wflose actl¥1ty they Influence. When stlmulated,lhe outefhalrc4!11s c.1n ;u:ttvely amplify the traveling w.ave. This increases the sensitivity of !he inner hair cells (the actual receptor cells). The activity of the efferaru from the olive can be recorded as otoacoustlc emissiOn$ (OAE). This ll!St can be used to saeen for hearing abnormalities 11'1 newborns.

367

12.22 Vestibular System

,.

VE!il--- --1-- - Nud...d trachletr nerw 1.\ldnllll fudwha

NudiiUSd lbWant:MM!

~b""

t~ntllcn

- - - - --ff----....

__, ,. Utllde

To amcal mid

A cennl connectiON olthe WS11bul•rnerw Three systEms are lrwolved In the reguldlon of human balance: • Vestlbulu systEm • PrapriDCeptiVI! sysmm • VlsUil system The litter two systems h- alre.~dy bHn described. The perlpher;ll receptors of the wstfblllarlfSCim 1re loab!d In the membr.mous labyrinth (see petrGuJ bone, pp. 1 buds clean to allow for new tasting. Humans Cin perce!Ye five bisslc taste q~aalltfes: sweet, $OUr, salty. bitter. and a flfth •savory" qwllty, called umaml, which Is activated by glutamatz {a tiLrtt! enhancer).

Ught

b151etll!ll

C M'roscopfutructure of ;a tillte bud Nerves Induce the formalfon or taste buds In Ule oral mucosa. Ax.ons of cranial nel'lll!!s VII, IX. and Xgrow into !he oral mucosa from the basal slde and Induce the epithelium to dlfferentlilte lnbl the light and dark taste cells(= mod11!ed eptthdlal cells). Both types of taste cell have mlcrOYllll that extend to the gustatory pore. FGr $OUr ind $alty, the taste cell is stimulated by hydrogen ions and other cations. The othet" taste q~aalltfes are mediated by receptor proteins to which the liM-molecularweight flavored subst.lnces bind {details may be found In textbooks of physiology). When !he low-molewlar-welght flavored substances bind to the receptor proteins, they induce signal transduction ttlat causes the release of glut
12. Functional S}tmms

12.24 Olfactory System (Smell)

Longltudnalstl'lle

lntl!!l>edu naln

nuc:!Ns

Medl~l O~(b)ly

Hilbl!nular

nuclei

stria Tegrnerul nuc:!Ns

O~(b)ly

bulb ~wl!h

Olfltcb)ry flbe-s

•

~~~

b
Olliu:blry

mucosa

-

i'replrifonn

A Olflrc:tory system: tfle olfactory m-a and Its Ol!lltral conntctt:ons

Olfactory tract viewed In mlds;rgltt111l Cllrtec: does not"-

• slx~.yered 1 rc:hiiKtuiW

.-.c.

bodies, nudeus io:umbcns, and h1ba1ullr nudeus. Its bratlutlm