Parts of the brain pdf - Head and Neck

544

CHAPTER 11

The Head and Neck

Cerebral hemorrhage

The pituitary gland, which lies medially in the sella

nerve (Fig. 11.12).

the ophthalmic and maxillary divisions of the 5th cranial

In the lateral wall, the 3rd and 4th cranial nerves, and

which travel through it (Fig. 11.12)

The internal carotid artery and the 6th cranial nerve,

the Cavernous Sinuses

Important Structures Associated with

connect the two cavernous sinuses through the sella turcica.

through the superior petrosal sinus. Intercavernous sinuses

ina. The sinus drains posteriorly into the transverse sinus

the inferior ophthalmic vein and the central vein of the ret

the sphenoid bone (Fig. 11.9). Anteriorly, the sinus receives

lies on the lateral side of the body of

cavernous sinus

Each

through the foramen magnum and the transverse sinuses.

falx cerebelli. It communicates with the vertebral veins

lies in the attached margin of the

occipital sinus

The

jugular vein (Fig. 11.30).

skull through the jugular foramen to become the internal

mastoid antrum of the temporal bone and then leaves the

transverse sinuses. Each sinus turns downward behind the

are a direct continuation of the

sigmoid sinuses

The

the sigmoid sinus.

tentorium cerebelli, and they end on each side by becoming

11.10). Each sinus lies in the lateral attached margin of the

usually a continuation of the straight sinus (Figs. 11.9 and

left transverse sinus

of the superior sagittal sinus; the

begins as a continuation

right transverse sinus

The

vein, it drains into the left transverse sinus.

union of the inferior sagittal sinus with the great cerebral

ebri with the tentorium cerebelli (Fig. 11.9). Formed by the

lies at the junction of the falx cer

straight sinus

The

veins from the medial surface of the cerebral hemisphere.

vein to form the straight sinus (Fig. 11.9). It receives cerebral

the falx cerebri. It runs backward and joins the great cerebral

lies in the free lower margin of

inferior sagittal sinus

The

superior cerebral veins.

lacunae (Fig. 11.2). The superior sagittal sinus receives the

Numerous arachnoid villi and granulations project into the

venous lacunae.

sinus communicates on each side with the

becomes continuous with the right transverse sinus. The

der of the falx cerebri (Fig. 11.9). It runs backward and

lies in the upper fixed bor

superior sagittal sinus

The

diploë of the skull, the orbit, and the internal ear.

have no valves. They receive tributaries from the brain, the

of fibrous tissue; they have no muscular tissue. The sinuses

are lined by endothelium. Their walls are thick and composed

situated between the layers of the dura mater (Fig. 11.2); they

The venous sinuses of the cranial cavity are blood-filled spaces

The Venous Blood Sinuses

the

great cerebral veins,

Bleeding then takes place from the

anteroposterior compression of the head often tears the ante

occur from the cerebral veins or the venous sinuses. Excessive

diately loses consciousness, and the paralysis is evident when

is generally caused by rupture of the

thin-walled lenticulostriate artery, a branch of the middle cere-

bral artery. The hemorrhage involves the vital corticobulbar

and corticospinal fibers in the internal capsule and produces

hemiplegia on the opposite side of the body. The patient imme-

consciousness is regained.

Intracranial Hemorrhage in the Infant

Intracranial hemorrhage in the infant may occur during birth and

may result from excessive molding of the head. Bleeding may

rior attachment of the falx cerebri from the tentorium cerebelli.

straight sinus, or the inferior sagittal sinus.

■

turcica (Fig.11.12)
The veins of the face, which are connected with

■

the cavernous sinus via the facial vein and inferior
ophthalmic vein, are an important route for the spread
of infection from the face (Fig. 11.9)

described.

the following account, only the main parts of the brain are

brain, a textbook of neuroanatomy should be consulted. In

For a detailed description of the gross structure of the

gland is vital to life and is fully described on page 652.

tion in the sella turcica of the sphenoid bone. The pituitary

11.12). The gland is well protected by virtue of its loca

(Fig.

infundibulum

the undersurface of the brain by the

The pituitary gland is a small, oval structure attached to

Pituitary Gland (Hypophysis Cerebri)

the temporal bone (Fig. 11.9)

along the upper and lower borders of the petrous part of

which run

inferior petrosal sinuses,

superior

The

■

and

Parts of the Brain

Major Parts of the Brain

Cavities of the Brain

Forebrain

Cerebrum

Diencephalon

Right and left lateral

ventricles

Third ventricle

Midbrain

Hindbrain

Pons

Medullaoblongata

Cerebellum

Cerebral aqueduct

Fourth ventricle

and central

canal

bones; above the anterior and middle cranial fossae; and,

Each hemisphere extends from the frontal to the occipital

(Fig. 11.13).

corpus callosum

of white matter called the

connected by a mass

cerebral hemispheres

sists of two

is the largest part of the brain and con

cerebrum

The

cord through the foramen magnum.

lies inside the cranial cavity. It is continuous with the spinal

The brain is that part of the central nervous system that

Cerebrum

posteriorly, above the tentorium cerebelli. The hemispheres

(Fig. 11.2). The cerebral

gray matter

and is composed of

cortex

The surface layer of each hemisphere is called the

(Fig. 11.13).

falx cerebri

which projects the

into

longitudinal fissure,

are separated by a deep cleft, the

Basic Anatomy

545

superior sagittal sinus

inferior sagittal sinus

interthalamic connection

thalamus

falx cerebri

great

cerebral vein

pineal

cerebral

aqueduct

midbrain

tentorium

cerebelli

straight

sinus

fourth ventricle

cerebellum

pons

medulla oblongata

atlas

ligamentum nuchae

opening of auditory tube

postvertebral muscles

cervical spines

spinal cord

central canal

brachiocephalic artery

left brachiocephalic vein

manubrium sterni

remnants of thymus

jugular arch

investing layer of

deep cervical fascia

isthmus of thyroid gland

esophagus

trachea

cricothyroid ligament

thyroid cartilage

vocal fold

vestibular fold

epiglottis

thyrohyoid membrane

hyoid bone

tonsil

mylohyoid

geniohyoid

genioglossus

tongue

soft palate

hard palate

inferior
concha

vestibule

of nose

middle concha

agger nasi

superior concha

frontal sinus

hypophysis cerebri

optic nerve

anterior cerebral artery

interventricular foramen

septum pellucidum

corpus callosum

fornix

suprasternal space

arch of cricoid cartilage

FIGURE 11.13

Sagittal section of the head and neck.

occipital lobe

sulcus. The

is situated behind the central sulcus and above the lateral

parietal lobe

The

lateral sulcus.

(Fig. 11.14) and above the

central sulcus

is situated in front of the

frontal lobe

The

(Fig. 11.14).

named for the bones of the cranium under which they lie

The lobes are

lobes.

the surface of each hemisphere into

increased. Several of the large sulci conveniently subdivide

By this means, the surface area of the cortex is greatly

sulci.

separated by fissures,

gyri,

cortex is thrown into folds, or

lies below the

position, with the nerve cells controlling the movements

In the motor area, the body is represented in an inverted

gata as they descend to the spinal cord.

fibers cross over to the opposite side in the medulla oblon

movements on the opposite side of the body. Most nerve

The large motor nerve cells in this area control voluntary

(Fig. 11.14).

motor area

central sulcus and is known as the

lies immediately anterior to the

precentral gyrus

The

lobe.

temporal

Below the lateral sulcus is situated the

sulcus.

parietooccipital

546

CHAPTER 11

The Head and Neck

central sulcus

sensory area

parietal lobe

parieto-occipital sulcus

occipital lobe

visual area

superotemporal gyrus

cerebellum

medulla oblongata

pons

auditory area

temporal lobe

lateral sulcus

anterior

motor speech area
(if right hemisphereis
dominant)

frontal lobe

premotor area

motor area

branches of anterior
cerebral artery

anterior

middle
cerebral
artery

branches of posterior
cerebral artery

anterior
cerebral
artery

branches of middle
cerebral artery

posterior
cerebral
artery

foot

face

FIGURE 11.14

by the anterior cerebral artery; those colored red, by the middle cerebral artery; and those colored green, by the posterior

hemisphere showing areas supplied by the cerebral arteries. In this and the next figure, areas colored

Lateral surface of the cerebral

speech area is most commonly located in the left rather than the right cerebral hemisphere.

Right side of the brain showing some important localized areas of cerebral function. Note that the motor

blue are supplied

cerebral artery.

the movements of the face and hands in the lower part

of the feet located in the upper part and those controlling

Medial surface of the cerebral hemisphere showing the areas supplied by the cerebral arteries.

(Fig. 11.14).

The lateral ventri

lateral ventricle.

sphere is called the

The cavity present within each cerebral hemi

visual impressions.

(Fig. 11.14). It is the receiving area for

calcarine sulcus

medial aspect of the cerebral hemisphere in the region of

is situated on the posterior pole and

visual area

The

left-handed persons.

in right-handed persons and in the right hemisphere in

employed in speech. It is dominant in the left hemisphere

the lateral sulcus (Fig. 11.14). It controls the movements

lies just above

motor speech area,

or the

Broca’s area,

auditory area.

and is known as the

concerned with the reception and interpretation of sound

the lateral sulcus (Fig. 11.14). The middle of this gyrus is

lies immediately below

superior temporal gyrus

The

from the opposite side of the body.

pret sensations of pain, temperature, touch, and pressure

11.14). The small nerve cells in this area receive and inter

(Fig.

sensory area

the central sulcus and is known as the

lies immediately posterior to

postcentral gyrus

The

the

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-

cles communicate with the third ventricle through the

the hindbrain (Fig. 11.13).

through the tentorial notch and connects the forebrain to

The midbrain is the narrow part of the brain that passes

posterior perforated substance.

mammillary bodies,

infundibulum,

cinereum

tuber

(Fig. 11.15), the

optic chiasma

before backward: the

tures are found in the floor of the third ventricle from

wall and floor of the third ventricle. The following struc

The hypothalamus forms the lower part of the lateral

pathway to the cerebral cortex.

tricle. It is the great relay station on the afferent sensory

mass of gray matter that lies on either side of the third ven

The thalamus is a large

hypothalamus.

11.13) and a ventral

(Fig.

thalamus

surface of the brain. It consists of a dorsal

The diencephalon is almost completely hidden from the

(Fig. 11.13).

interventricular foramina

Diencephalon

and the

the

and the

Midbrain

Basic Anatomy

547

anterior cerebral artery

longitudinal cerebral fissure

optic nerve

optic chiasma

optic tract

mammillary body

oculomotor

nerve

trochlear

nerve

trigeminal

nerve

abducent

nerve

facial nerve

vestibulo-

cochlear nerve

vagus nerve

accessory nerve
(cranial part)

hypoglossal nerve

cerebellum

medulla oblongata

anterior spinal artery

pyramid

vertebral artery

basilar artery

olive

anteroinferior

cerebellar artery

pontine arteries

superior

cerebellar artery

posterior

cerebral artery

posterior

communicating artery

internal
carotid artery

middle cerebral artery

infundibulum

anterior
communicating artery

olfactory tract

olfactory bulb

glossopharyngeal

nerve

FIGURE 11.15

ace of the brain. To show the course of the middle cerebral

Arteries and cranial nerves seen on the inferior surf

produced

cuneate tubercles,

gracile

oblongata are the

On the posterior surface of the inferior part of the medulla

which connect the medulla to the cerebellum.

cles,

inferior cerebellar pedun

11.15). Behind the olives are the

(Fig.

olivary nuclei

elevations produced by the underlying

which are oval

olives,

Posterior to the pyramids are the

decussation of the pyramids.

the opposite side, forming the

below, and here most of the descending fibers cross over to

precentral gyrus of the cerebral cortex. The pyramids taper

dles of nerve fibers that originate in large nerve cells in the

(Fig. 11.15). The pyramids are composed of bun

pyramid

medulla, and on each side of this is a swelling called the

is present on the anterior surface of the

median fissure

nects the pons above to the spinal cord below (Fig. 11.13).

is conical in shape and con

medulla oblongata

The

cranial nerve nuclei.

within the pons serve as relay stations, whereas others form

the midbrain, and the spinal cord. Some of the nerve cells

ascending and descending fibers connecting the forebrain,

connect the two halves of the cerebellum. It also contains

(Fig. 11.13). It is composed mainly of nerve fibers, which

lum below the midbrain and above the medulla oblongata

is situated on the anterior surface of the cerebel

pons

The

middle age, and thus it can be visualized on radiographs.

tricle (see also page 656). The pineal commonly calcifies in

a stalk to the region of the posterior wall of the third ven

between the superior colliculi (Fig. 11.13). It is attached by

is a small glandular structure that lies

pineal body

The

lum and the cerebral hemispheres.

The colliculi are deeply placed between the cerebel

two inferior col

(Fig. 11.12) and

two superior

namely, the

to the cerebral aqueduct; it has four small surface swellings,

is the part of the midbrain posterior

tectum

ventricles. The

which connects the third and fourth

cerebral aqueduct,

(Fig. 11.12). The narrow cavity of the midbrain is the

nigra

substantia

by a pigmented band of gray matter, the

tegmen

and a posterior part, the

crus cerebri;

rior part, the

each of these is divided into an ante

cerebral peduncles;

The midbrain comprises two lateral halves called the

artery, the anterior pole of the left temporal lobe has been removed.

tum,

liculi.

Hindbrain

and

548

CHAPTER 11

by the medially placed underlying

The Head and Neck

nucleus gracilis

sinus (Fig. 11.9).

and drains into the straight

internal cerebral veins

the two

is formed by the union of

great cerebral vein

present. The

Cerebral and cerebellar veins and veins of the brainstem are

brain and drain into the cranial venous sinuses (Fig. 11.2).

walls, and they possess no valves. They emerge from the

The veins of the brain have no muscular tissue in their thin

Veins of the Brain

the circle of Willis are fully described on pages 598 and 599.

The internal carotid arteries, the vertebral arteries, and

(circulus arteriosus).

circle of Willis

inferior surface of the brain and form the

two vertebral arteries. The four arteries anastomose on the

The brain is supplied by the two internal carotid and the

Arteries of the Brain

(Figs 11.124, 11.125, and 11.126)

phy (CT) scans and magnetic resonance imaging (MRI).

cles may be visualized clinically using computed tomogra

fourth ventricle. The size and shape of the cerebral ventri

of the two lateral ventricles, the third ventricle, and the

choroid plexuses

spinal fluid, which is produced by the

subarachnoid space. The ventricles are filled with cerebro

cord and, through the three foramina in its roof, with the

of the spinal

central canal

is continuous with the narrow

The fourth ventricle, in turn,

cerebral aqueduct.

by the

third ventricle communicates with the fourth ventricle

(Fig. 11.13); the

interventricular foramina

through the

third ventricle

communicate with the

lateral ventricles

cles, the third ventricle, and the fourth ventricle. The two

The ventricles of the brain consist of the two lateral ventri

Ventricles of the Brain

a median and two lateral openings.

space through three openings in the lower part of the roof:

of the spinal cord. It communicates with the subarachnoid

aqueduct, and below it is continuous with the central canal

cle is connected above to the third ventricle by the cerebral

and the cerebellum. The fourth ventri

rior medullary vela

infe

superior

medulla oblongata and behind by the

(Fig. 11.13). This is bounded in front by the pons and the

The cavity of the hindbrain is the fourth ventricle

the same side of the body.

muscle tone and the coordination of muscle movement on

The cerebellum plays an important role in the control of

dentate nucleus.

matter; the largest of these is known as the

in the interior of the cerebellum, embedded in the white

transverse fissures. Certain masses of gray matter are found

separated by closely set

folia,

tex is thrown into folds, or

is composed of gray matter. The cerebellar cor

cortex,

The surface layer of each cerebellar hemisphere, called

inferior cerebellar peduncles.

and to the medulla by the

middle cerebellar peduncles,

to the pons by the

superior cerebellar peduncles,

by the

The cerebellum is connected to the midbrain

vermis.

sists of two hemispheres connected by a median portion,

posterior to the pons and the medulla oblongata. It con

beneath the tentorium cerebelli (Fig. 11.13). It is situated

lies within the posterior cranial fossa

cerebellum

The

nucleus cuneatus.

laterally placed underlying

and the

the

and

-
-

Blood Supply of the Brain

may produce severe cerebral damage, stretching and distor

Injuries of the brain are produced by displacement and distor

Brain Injuries

tion of the neuronal tissues at the moment of impact. The brain

may be likened to a log soaked with water floating submerged

in water. The brain is floating in the cerebrospinal fluid in the

subarachnoid space and is capable of a certain amount of

anteroposterior movement, which is limited by the attachment

of the superior cerebral veins to the superior sagittal sinus.

Lateral displacement of the brain is limited by the falx cerebri.

The tentorium cerebelli and the falx cerebelli also restrict dis-

placement of the brain.

It follows from these anatomic facts that blows on the front

or back of the head lead to displacement of the brain, which

tion of the brainstem, and stretching and even tearing of the

commissures of the brain. The terms concussion, contusion,

and laceration are used clinically to describe the degrees of

brain injury.

Blows on the side of the head produce less cerebral

displacement, and the injuries to the brain consequently tend

to be less severe.

C L I N I C A L N O T E S

The Cranial Nerves in the Cranial Cavity

The 12 pairs of cranial nerves are named as follows:

I. Olfactory (sensory)

II. Optic (sensory)

III. Oculomotor (motor)

IV. Trochlear (motor)

V. Trigeminal (mixed)

VI. Abducent (motor)

VII. Facial (mixed)

VIII. Vestibulocochlear (sensory)

IX. Glossopharyngeal (mixed)

X. Vagus (mixed)

XI. Accessory (motor)

XII. Hypoglossal (motor)

skull are summarized in Table 11.6.

tion, and the openings through which they exit from the

The cranial nerves, their component parts, their func

on page 605.

origins and courses of the cranial nerves are described

entirely motor; and the remaining nerves are mixed. The

lear, abducent, accessory, and hypoglossal nerves are

lear nerves are entirely sensory; the oculomotor, troch

and abdomen. The olfactory, optic, and vestibulococh

the vagus, which also supplies structures in the thorax

All the nerves are distributed in the head and neck except

through foramina and fissures in the base of the skull.

The nerves emerge from the brain and are transmitted

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