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TM

FIFTH
EDITION

Neuroanatomy



TM

FIFTH
EDITION

Neuroanatomy
Douglas J. Gould, PhD
Professor and Vice Chair
Department of Biomedical Sciences
William Beaumont School of Medicine

Oakland University
Rochester, Michigan

Jennifer K. Brueckner-Collins, PhD
Professor and Vice Chair
Department of Anatomical Sciences and Neurobiology
University of Louisville School of Medicine
Louisville, Kentucky
Author of First-Fourth Editions:

James D. Fix, PhD
(1931–2010)


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Fifth edition
Copyright © 2016 Wolters Kluwer.
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I dedicate this work to my beloved wife, Marie. Your strength, courage, and love are the engine that
moves our family forward and provides the foundation for our girls to grow into proud, strong women.
I love you. Thank you.
Douglas J. Gould

I dedicate my contributions to this book to my son, Lincoln. You are the light of my life and you make
each and every day meaningful and fun! You have already taught me a lifetime of lessons about love,
life, and the importance of play in the short 9 1/2 months that we have had together and I am eternally
grateful to you for that. I hope that we will have the blessed opportunity to share many more years
learning from and loving each other. I love you to the moon and back, my sweet bunny.
Jennifer K. Brueckner-Collins



PREFACE

Based on your feedback on previous editions of this text, the fifth edition has been reorganized and
updated significantly in order to provide an accurate and quick review of important clinical aspects of
neuroanatomy for the future physician. New features include the replacement of the “key concepts”
with more focused “objectives” for each chapter, driving the content, order, and level of detail. The
chapters have been reordered and recombined to group “like” topic more closely. A new Gross Structure chapter has been incorporated to lay the foundation for understanding the sectional anatomy in
the Atlas chapter. The fourth edition’s Thalamus and Hypothalamus chapters are now integrated in the
fifth edition as a new Diencephalon chapter; the previous Spinal cord, Spinal cord tracts, and Spinal
cord lesions chapters are combined in a centralized Spinal Cord chapter; and the former Brainstem and
Brainstem lesions chapters are united in a new Brainstem chapter. Terminology updates have been
included to ensure consistency with Terminologica Anatomica.
We would appreciate receiving your comments and/or suggestions concerning High-Yield™
Neuroanatomy Fifth Edition especially after you have taken the USMLE Step 1 examination. Your
suggestions will find their way into the sixth edition. You may contact us at or


vii

CONTENTS

Preface

1

vii

GROSS STRUCTURE OF THE BRAIN

1

I Divisions of the Brain 1

2

DEVELOPMENT OF THE NERVOUS SYSTEM
I
II
III
IV
V
VI
VII
VIII
IX

3

NEUROHISTOLOGY

I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
XIII

4

13

17

Neurons 17
Nissl Substance 17
Axonal Transport 17
Anterograde (Wallerian) Degeneration
Chromatolysis 18
Regeneration of Nerve Cells 18
Neuroglia 19
The Blood–Brain Barrier 19
The Blood–CSF Barrier 19
Pigments and Inclusions 20

Classification of Nerve Fibers 21
Tumors of the CNS and PNS 21
Cutaneous Receptors 23

BLOOD SUPPLY
I
II
III
IV
V

viii

The Neural Tube 10
The Neural Crest 10
The Cranial Neuropore 12
The Caudal Neuropore 12
Microglia 12
Myelination 12
The Optic Nerve and Chiasma 12
The Hypophysis (pituitary gland) 12
Congenital Malformations of the CNS

18

25

The Spinal Cord and Caudal Brainstem 25
The Internal Carotid System 25
The Vertebrobasilar System 27

The Blood Supply of the Internal Capsule 28
Veins of the Brain 28

10


Contents

VI Venous Dural Sinuses 29
VII Angiography 29
VIII The Middle Meningeal Artery

5

MENINGES, VENTRICLES, AND
CEREBROSPINAL FLUID 36
I
II
III
IV

6

29

Meninges 36
Ventricular System 38
Cerebrospinal Fluid 39
Herniation 39

SPINAL CORD
I
II
III
IV
V
VI

44

Gray and White Rami Communicans 44
Spinal Nerves 44
Conus Medullaris 44
Location of the Major Motor and Sensory Nuclei of the Spinal Cord
The Cauda Equina 47
The Myotatic Reflex 47

Case 6-1 49
I Posterior (Dorsal) Column—Medial Lemniscus Pathway
II Anterolateral System 51
III Lateral Corticospinal Tract 51

49

Case 6-2 54
I Diseases of the Motor Neurons and Corticospinal Tracts 54
II Sensory Pathway Lesions 55
III Combined Motor and Sensory Lesions 55
IV Peripheral Nervous System (PNS) Lesions 57
V Intervertebral Disk Herniation 57

VI Cauda Equina Syndrome (Spinal Roots L3 to C0) 57
VII Conus Medullaris Syndrome (Cord Segments S3 to C0) 58

7

BRAINSTEM
I
II
III
IV
V
VI
VII
VIII
IX
X

59

Introduction 59
Cross Section Through the Caudal Medulla 59
Cross Section Through the Mid-Medulla 59
Cross Section Through the Rostral Medulla 61
Cross Section Through the Caudal Pons 62
Cross Section Through the Mid-Pons 63
Cross Section Through the Rostral Pons 63
Cross Section Through the Caudal Midbrain 64
Cross Section Through the Rostral Medulla 64
Corticonuclear Fibers 64

45

ix


x

Contents

Lesions of the Brainstem 65
I Lesions of the Medulla 65
II Lesions of the Pons 65
III Lesions of the Midbrain 66
IV Acoustic Neuroma (Schwannoma) 67
V Jugular Foramen Syndrome 67
VI “Locked-in” Syndrome 68
VII Central Pontine Myelinolysis 68
VIII “Top of the Basilar” Syndrome 68
IX Subclavian Steal Syndrome 68
X The Cerebellopontine Angle 68

8

AUTONOMIC NERVOUS SYSTEM
I
II
III
IV
V

9

10

75

The Olfactory Nerve 75
The Optic Nerve (CN II) 75
The Oculomotor Nerve (CN III) 76
The Trochlear Nerve (CN IV) 77
The Trigeminal Nerve (CN V) 78
The Abducent Nerve (CN VI) 80
The Facial Nerve (CN VII) 80
The Vestibulocochlear Nerve (CN VIII) 82
The Glossopharyngeal Nerve (CN IX) 83
The Vagal Nerve (CN X) 84
The Accessory Nerve (CN XI) 85
The Hypoglossal Nerve (CN XII) 85

TRIGEMINAL SYSTEM
I
II
III
IV
V

11

Introduction 70
Cranial Nerves (CN) With Parasympathetic Components

Communicating Rami 73
Neurotransmitters 73
Clinical Correlation 73

CRANIAL NERVES
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII

70

87

Introduction 87
The Trigeminal Ganglion 87
Trigeminothalamic Pathways 88
Trigeminal Reflexes 89
The Cavernous Sinus 90

DIENCEPHALON
I Introduction 92

II The Thalamus 92

92

71


Contents

III Blood Supply 94
IV The Internal Capsule 94
V The hypothalamus 95

12

AUDITORY SYSTEM
I
II
III
IV

13

16

108

Introduction 108
The Visual Pathway 108
The Pupillary Light Reflex Pathway 111

The Pupillary Dilation Pathway 111
The Near Reflex and Accommodation Pathway 112
Cortical and Subcortical Centers for Ocular Motility 113
Clinical Correlation 114

LIMBIC SYSTEM
I
II
III
IV

104

Introduction 104
The Labyrinth 104
The Vestibular Pathways 104
Vestibulo-ocular Reflexes 106

VISUAL SYSTEM
I
II
III
IV
V
VI
VII

15

Introduction 100

The Auditory Pathway 100
Hearing Defects 102
Auditory Tests 102

VESTIBULAR SYSTEM
I
II
III
IV

14

100

116

Introduction 116
Major Components 116
The Papez Circuit 116
Clinical Correlations 118

BASAL NUCLEI AND EXTRAPYRAMIDAL
MOTOR SYSTEM 120
I Basal Nuclei (Ganglia) 120
II The Extrapyramidal (Striatal) Motor System
III Clinical Correlation 121

17

CEREBELLUM

I
II
III
IV

126

Function 126
Anatomy 127
The Deep Cerebellar Nuclei 128
The Major Cerebellar Circuit 128

120

xi


xii

Contents

V Cerebellar Dysfunction 129
VI Cerebellar Syndromes and Tumors

18

CEREBRAL CORTEX
I
II
III

IV
V
VI
VII
VIII
IX
X
XI

19

131

Introduction 131
The Six-Layered Neocortex 131
Functional Areas 132
Focal Destructive Hemispheric Lesions and Symptoms
Cerebral Dominance 135
Split Brain Syndrome 137
Other Lesions of the Corpus Callosum 138
Brain and Spinal Cord Tumors 138
Apraxia 138
Aphasia 139
Dysprosodies 140

135

CROSS-SECTIONAL ANATOMY OF THE BRAIN
I Introduction

20

129

142

NEUROTRANSMITTERS

161

I Major Neurotransmitters 161
II Functional and Clinical Considerations

165

Appendix I: Table of Cranial Nerves 167
Appendix II: Table of Common Neurological Disease States
Glossary 173
Index 183

142

170


CHAPTER 1

Gross Structure
of the Brain
Objectives

1. Describe the telencephalon including the lobes of the cerebral hemispheres and the major gyri, sulci
and lobules of each.

2. Differentiate the structures of the limbic and olfactory senses from other parts of the brain.
3. List the different parts of the diencephalon, brainstem, and cerebellum.

I

Divisions of the Brain.

The brain consists of five divisions: telencephalon,

diencephalon, mesencephalon, metencephalon, and myelencephalon.

A. Telencephalon consists of the cerebral hemispheres and the basal nuclei. The cerebral hemi-

spheres contain the lateral ventricles.
1. Cerebral hemispheres (Figures 1-1 to 1-3) consist of six lobes and the olfactory structures:
a. Frontal lobe extends from the central sulcus to the frontal pole and lies superior to the lateral
sulcus. It contains:
● Precentral gyrus—consists of the primary motor area (area 4).
● Superior frontal gyrus—contains supplementary motor cortex on the medial surface
(area 6).
● Middle frontal gyrus—contains the frontal eye field (area 8).
● Inferior frontal gyrus—contains the Broca speech area in the dominant hemisphere
(areas 44 and 45).
● Gyrus rectus and orbital gyri—separated by the olfactory sulcus.
● Anterior paracentral lobule—found on the medial surface between the superior frontal
gyrus (paracentral sulcus) and the central sulcus.
b. Parietal lobe extends from the central sulcus to the occipital lobe and lies superior to the temporal lobe.

● Postcentral gyrus—the primary somatosensory area of the cerebral cortex (areas 3, 1,
and 2).
● Superior parietal lobule comprises association areas involved in somatosensory functions
(areas 5 and 7).
● Inferior parietal lobule consists of the supramarginal gyrus, which interrelates somatosensory, auditory, and visual inputs (area 40) and the angular gyrus (area 39) that receives
impulses from primary visual cortex.
● Precuneus—located between the paracentral lobule and the cuneus.
● Posterior paracentral lobule—located on the medial surface between the central sulcus
and the precuneus.
1


2

Chapter 1
Superior parietal
lobule Interparietal
sulcus
Parietal lobe

Precentral Central sulcus
sulcus

id

tral

gyr
tral

tcen

al

cen

nt

us

Supramarginal
gyrus
Angular
gyrus

Inferior frontal gyrus

pe
Su
Orbital gyrus

Mid

dle

l

ora

mp

te
rior

Broca's motor
speech area

Inferior parietal
lobule

gyr

us
M

dle

fro

r
gy

Pos

Superior frontal
sulcus

Inferior frontal
sulcus

us

Superior frontal
gyrus

Pre

Frontal lobe

p
tem

ora

Wernicke's
area

us
gyr

l gy

por
tem
r
o
s
ri
ru
Infe gy

Occipital
lobe

rus

al

Lateral (Sylvian)
sulcus
Temporal lobe
Superior temporal
sulcus
Middle temporal
sulcus

Figure 1-1 Lateral surface of the brain showing the principal gyri and sulci.

Cingulate gyrus

Parietal lobe

Corpus callosum
Posterior commissure
Septum pellucidum

Superior and
inferior collilculi

Frontal

lobe

Parieto-occipital
sulcus

Superior
frontal
gyrus

Occipital
lobe
Occipital
pole

Frontal
pole

Calcarine
fissure
(sulcus)

Anterior
commissure
Hypothalamus
Thalamus

Midbrain
Cerebellum
Pons
Medulla

Spinal cord

Figure 1-2 Midsagittal section of the brain and brainstem showing the structures surrounding the third and fourth
ventricles.


Gross Structure of the Brain

3

Prefrontal cortex
Gyrus rectus

Olfactory bulb

Medial olfactory stria
Lateral olfactory stria
Olfactory tract

Mammillary bodies

Middle temporal
gyrus

Optic chiasm

Uncus

Inferior temporal

gyrus
Inferior temporal
sulcus

Parahippocampal
gyrus

Collateral
sulcus

Occipitotemporal
gyrus

Pons

Olive

Pyramid

Figure 1-3 Inferior surface of the brain showing the principal gyri and sulci.

c. Temporal lobe extends from the temporal pole to the occipital lobe, inferior to the lateral sulcus.

It contains:

●
●
●
●
●

Transverse temporal gyrus (of Heschl)—found within the lateral sulcus. It contains the
primary auditory areas of the cerebral cortex (areas 41 and 42).
Superior temporal gyrus—associated with auditory functions and contains the
Wernicke speech area in the dominant hemisphere (area 22).
Middle temporal gyrus
Inferior temporal gyrus
Lateral occipitotemporal gyrus (fusiform gyrus)—lies between the inferior temporal

sulcus and the collateral sulcus.

d. Occipital lobe lies posterior to a line connecting the parieto-occipital sulcus and the preoc-

cipital notch. It contains two structures:
Cuneus—situated between the parieto-occipital sulcus and the calcarine sulcus and contains the visual cortex (areas 17, 18, and 19).
● Lingual gyrus lies inferior to the calcarine sulcus and contains the visual cortex (areas 17,
18, and 19).
e. Insular lobe (insula) lies within the lateral sulcus.
●


4

Chapter 1
Postcommissural
fornix
Anterior
Corpus callosum
nucleus

Cingulate gyrus
Precommissural
fornix

Fornix

Anterior
commissure

Septal
area

Medial
hypothalamus

Amygdala
Mammillary
body

Stria
terminalis

Hippocampal
formation

Figure 1-4 Midsagittal section of the brain showing the components of the limbic lobe.

f. Limbic lobe (Figure 1-4)—a C-shaped collection of structures found on the medial hemi-

spheric surface that encircles the corpus callosum and the lateral aspect of the midbrain. It

includes:
● Paraterminal gyrus and subcallosal area—located anterior to the lamina terminalis and
inferior to the rostrum of the corpus callosum.
● Cingulate gyrus lies parallel and superior to the corpus callosum and merges with the
parahippocampal gyrus.
● Parahippocampal gyrus lies between the hippocampal and collateral sulci and terminates
in the uncus.
● Hippocampal formation (Figure 1-5)—connected to the hypothalamus and septal area
via the fornix.
g. Olfactory structures—found on the orbital (inferior) surface of the brain and include the following:
● Olfactory bulb and tract represent an outpouching of the telencephalon. The olfactory
bulb receives the olfactory nerve (CN I).

Olfactory trigone and striae
Anterior perforated substance created by penetrating striate arteries.
Diagonal band of Broca interconnects the amygdaloid nucleus and the septal area.
2. Basal nuclei (ganglia) (Figure 1-6) constitute the subcortical nuclei of the telencephalon and
●
●
●

include:

a. Caudate nucleus—part of the striatum, together with the putamen.
b. Putamen—part of the striatum, together with the caudate nucleus and part of the lentiform

nucleus along with the globus pallidus.

c. Globus pallidus—part of the lentiform nucleus, together with the putamen.
d. Subthalamic nucleus—part of the diencephalon that functions with the basal nuclei.

Gross Structure of the Brain
Septum pellucidum
Head of
caudate nucleus

Corpus callosum
(genu)

Internal capsule
(anterior limb)

Anterior horn
(lateral ventricle)

Interventricular foramen
(of Monro)
Putamen
Internal capsule
(genu)

Amygdala

Globus
pallidus

Hippocampus

Internal capsule

(posterior limb)
Third ventricle
Thalamus

Fornix

Tail of
caudate nucleus
Corpus callosum
(splenium)

Figure 1-5 Horizontal section of the brain showing the components of the internal capsule.
Body of caudate
nucleus
Stria terminalis

Thalamus
Head of caudate
nucleus

Putamen
Globus pallidus
Amygdala
Tail of caudate
nucleus

Figure 1-6 Schematic diagram of basal nuclei.

5

6

Chapter 1

3. Lateral ventricles (see Figure 1-5)—ependyma-lined cavities of the cerebral hemispheres that
contain CSF and choroid plexus. They communicate with the third ventricle via two interventricular foramina (of Monro) and are separated from each other by the septum pellucidum.
4. Cerebral cortex consists of a thin layer or mantle of gray matter that covers the surface of each
cerebral hemisphere and is folded into gyri that are separated by sulci.
5. White matter includes the cerebral commissures and the internal capsule.
a. Cerebral commissures (see Figure 1-2) interconnect the cerebral hemispheres and include
the following structures:
● Corpus callosum—the largest commissure of the brain and it interconnects the two hemispheres. It has four parts, including the rostrum, genu, body, and splenium.
● Anterior commissure—interconnects the olfactory bulbs with the middle and inferior
temporal lobes.
● Hippocampal commissure (commissure of the fornix)—located between the fornices
and inferior to the splenium of the corpus callosum.
b. Internal capsule (see Figure 1-5) consists of the white matter located between the basal nuclei
and the thalamus. It has five parts:
● Anterior limb—located between the caudate nucleus and putamen and contains a mixture
of ascending and descending fibers.
● Genu—located between the anterior and posterior limbs and contains primarily the corticonuclear (corticobulbar) fibers.
● Posterior limb—located between the thalamus and lentiform nucleus (comprising the
putamen and the globus pallidus) and is primarily made up of corticospinal fibers.
● Retrolenticular portion—located posterior to the lentiform nucleus and contains the
optic radiations.
Third ventricle
Internal capsule

Caudate nucleus (head)

Stria medullaris

Ant. nucleus (thalamus)

Habenular trigone

Stria terminalis
Lenticular nucleus
Pulvinar (thalamus)

Pineal body
Medial geniculate body
Sup. colliculus
Brachium of inf. colliculus
Inf. colliculus
Trochlear nerve (CN IV)
Sup. cerebellar peduncle
(brachium conjunctivum)
Middle cerebellar peduncle
(brachium pontis)
Inf. cerebellar peduncle
(restiform body)

Lat. geniculate body
Cerebral peduncle
Ant. medullary velum
Posterior median sulcus
Median eminence
Facial colliculus

Sulcus limitans
Vestibular area
Striae medullares
Hypoglossal trigone

Cuneate tubercle
Gracile tubercle

Vagal trigone

Tuberculum cinereum
Lat. funiculus

Posterior median sulcus

Obex

Posterior intermediate sulcus

Fasciculus cuneatus
Fasciculus gracilis

Figure 1-7 Posterior surface anatomy of the brainstem.

Posterolateral suclus


Gross Structure of the Brain
●

7

Sublenticular portion—located inferior to the lentiform nucleus and contains auditory

radiations.

B. Diencephalon (see Figures 1-2 and 1-7) receives the optic nerve (CN II) and consists of the following structures:
1. Epithalamus
2. (Dorsal) Thalamus—separated from the hypothalamus by the hypothalamic sulcus.
3. Hypothalamus (Figure 1-8)
4. Subthalamus (ventral thalamus)—inferior to the thalamus and lateral to the hypothalamus.
5. Third ventricle and associated structures.

C. Mesencephalon (Midbrain) (see Figures 1-7 and 1-8)—located between the diencephalon
and the pons and contains the cerebral aqueduct interconnecting the third and fourth ventricles.
1. Anterior surface

a. Cerebral peduncle
b. Interpeduncular fossa
i. Oculomotor nerve (CN III)
ii. Posterior perforated substance—created by the penetrating branches of the posterior

cerebral and posterior communicating arteries.
2. Posterior surface
a. Superior colliculus (visual system)
b. Brachium of the superior colliculus

Optic nerve
Caudate nucleus

Optic chiasm
Internal capsule

Lenticular nucleus
Optic tract
Ant. perforated substance
Tuber cinereum
Interpeduncular fossa
(post. perforated
substance)
Mamillary body

Cerebral peduncle
(crus cerebri)

CN III
CN IV
CN V (motor root)

Pons

CN V (sensory root)
CN VI

Middle cerebellar peduncle
CN VII
CN VII (nervus intermedius)

CN VIII
CN XII

Olive
Pyramid
First cervical n.

Figure 1-8 Anterior surface anatomy of the brainstem.

CN IX
CN X
CN XI
Pyramidal decussation


8

Chapter 1

c. Inferior colliculus (auditory system)
d. Brachium of the inferior colliculus
e. Trochlear nerve (CN IV)—the only cranial nerve to exit the brainstem from the posterior

aspect.

D. Pons (see Figures 1-7 and 1-8)—located between the midbrain and the medulla.
1. Anterior surface

a. Base of the pons
b. Cranial nerves, including trigeminal nerve (CN V), abducent nerve (CN VI), facial nerve (CN

VII), and vestibulocochlear nerve (CN VIII)
2. Posterior surface (rhomboid fossa)

a. Locus ceruleus contains the largest collection of norepinephrinergic neurons in the CNS.
b. Facial colliculus contains the abducent nucleus and internal genu of the facial nerve.
c. Sulcus limitans separates the alar plate from the basal plate.
d. Striae medullares of the rhomboid fossa divides the rhomboid fossa into the superior pontine portion and the inferior medullary portion.

E. Medulla Oblongata (myelencephalon) (see Figures 1-7 and 1-8)—located between the pons
and the spinal cord.
1. Anterior surface
a. Pyramid contains descending tracts.
b. Olive contains the inferior olivary nucleus.

Anterior lobe

Midbrain

Pons

Flocculonodular
lobe
Posterolateral
fissure

Primary
fissure
Posterior lobe

A

Anterior lobe
Primary

fissure

Lateral
hemisphere
Posterolateral
fissure

B

Vermis

Flocculonodular
lobe

Posterior lobe

Figure 1-9 Surface features of
the cerebellum from a lateral view
(A) and a posterior view (B).


Gross Structure of the Brain

9

c. Cranial nerves, including glossopharyngeal nerve (CN IX), vagus nerve (CN X), (spinal) acces-

sory nerve (CN XI), and hypoglossal nerve (CN XII)
2. Posterior surface
a. Gracile tubercle

b. Cuneate tubercle
c. Rhomboid fossa
i. Striae medullares of the rhomboid fossa
ii. Vagal trigone
iii. Hypoglossal trigone
iv. Sulcus limitans
v. Area postrema (vomiting center)

F. Cerebellum (Figures 1-7 and 1-9)—located in the posterior cranial fossa, attached to the brain-

stem by three cerebellar peduncles. It forms the roof of the fourth ventricle. It is separated from the
occipital and temporal lobes by the tentorium cerebelli and contains the following surface structures/
parts:
1. Hemispheres consist of two lateral lobes.
2. Vermis
3. Flocculus and vermal nodulus form the flocculonodular lobule.
4. Tonsil is a rounded lobule on the inferior surface of each cerebellar hemisphere. With increased
intracranial pressure, it may herniate through the foramen magnum.
5. Superior cerebellar peduncle connects the cerebellum to the pons and midbrain.
6. Middle cerebellar peduncle connects the cerebellum to the pons.
7. Inferior cerebellar peduncle connects the cerebellum to the pons and medulla.
8. Anterior lobe lies anterior to the primary fissure.
9. Posterior lobe is located between the primary and posterolateral fissures.
10. Flocculonodular lobe lies posterior to the posterolateral fissure.


CHAPTER 2

Development of the
Nervous System

Objectives
1. Describe the development of the neural tube, including the stages of development and the adult
derivatives of each brain vesicle.

2. Trace the lineage of the cells of the neural tube wall, including the alar and basal plates.
3. Identify the derivatives of the neural crest.
4. Describe the development of the brainstem as well as the general arrangement of motor versus
sensory components and somatic versus visceral components.

5. Describe the development of the pituitary (hypophysis).
6. List and characterize major congenital malformations of the central nervous system.

I

The Neural Tube (Figure 2-1) gives rise to the central nervous system (CNS)

(i.e., brain and spinal cord).

A. The brainstem and spinal cord are composed of plates separated by the sulcus limitans:
1. An alar plate—gives rise to sensory neurons.
2. A basal plate—gives rise to motor neurons (Figure 2-2).
3. Interneurons are derived from both plates.

B. The neural tube gives rise to three primary vesicles (forebrain, midbrain, and hindbrain), which
develop into five secondary vesicles (telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon) (Figure 2-3).

C. Alpha-fetoprotein (AFP) is found in the amniotic fluid and maternal serum. It is an indicator
of neural tube defects (e.g., spina bifida, anencephaly). AFP levels are reduced in mothers of fetuses
with Down syndrome.

II

The Neural Crest (see Figure 2-1) gives rise to:

A. The peripheral nervous system (PNS) (i.e., peripheral nerves and sensory and autonomic ganglia).
B. The following cells:

1. Pseudounipolar cells of the spinal and cranial nerve ganglia
2. Schwann cells (which elaborate the myelin sheath)
3. Multipolar cells of autonomic ganglia

10


Development of the Nervous System

11

Neural groove

Neural plate

Surface ectoderm

Notochord

Neural folds

Neural crest

Neural tube
Spinal (dorsal root)
ganglion
Alar plate (sensory)
Sulcus limitans
Basal plate (motor)

Central canal

Figure 2-1 Development of the neural tube and crest.

4.
5.
6.
7.
8.
9.
10.

Cells of the leptomeninges (the pia-arachnoid), which envelop the brain and spinal cord
Chromaffin cells of the suprarenal medulla (which elaborate epinephrine)
Pigment cells (melanocytes)
Odontoblasts (which elaborate predentin)
Cells of the aorticopulmonary septum of the heart
Parafollicular cells (calcitonin-producing C-cells)
Skeletal and connective tissue components of the pharyngeal arches
Pia mater

Roof plate (ependymal layer)
Pial blood vessels

Choroid
plexus

Tela choroidea
Semicircular
canals

FOURTH VENTRICLE
SSA nuclei
GSA column
SVA column
GVA column
GVE column
SVE column

Alar plate
Sulcus
limitans

Ampullae
Cochlea

Basal
plate
Skin

GSE column
Taste bud cell
Floor plate
Somatic striated muscle

(tongue)
Branchial striated muscle
(larynx)

Visceral epithelium
Smooth muscle

Figure 2-2 The brainstem showing the cell columns derived from the alar and basal plates. The seven cranial nerve
modalities are shown. GSA, general somatic afferent; GSE, general somatic efferent; GVA, general visceral afferent;
GVE, general visceral efferent; SSA, special somatic afferent; SVA, special visceral afferent; SVE, special visceral efferent.
(Adapted from Patten BM. Human Embryology. 3rd ed. New York: McGraw-Hill; 1969:298, with permission.)