Bones and External views of the skull pdf - Head and Neck

Basic Anatomy

529

natomy

asic

The head and neck region of the body contains many

and abdomen.

except the 10th, which also supplies structures in the chest

nerves are distributed to structures in the head and neck,

through foramina and fissures in the skull. All the cranial

12 pairs of cranial nerves, which leave the brain and pass

or in the cavities bounded by them. The brain gives rise to

special senses, the eye and the ear, lie within the skull bones

its covering meninges enclosed in the cranial cavity. The

The head is formed mainly by the skull with the brain and

area.

important structures compressed into a relatively small

The Head

Bones of the Skull

ered on the outer and inner surfaces with periosteum.

and more brittle than the external table. The bones are cov

(Fig. 11.2). The internal table is thinner

called the

of compact bone separated by a layer of spongy bone

tables

internal

external

The skull bones are made up of

of the cranium (Fig. 11.1).

is the lowest part

base of the skull

of the cranium, and the

is the upper part

vault

cranium and those of the face. The

The bones of the skull can be divided into those of the

by the mobile temporomandibular joint (see page 571).

dible is an exception to this rule, for it is united to the skull

The man

sutural ligament.

between the bones is called a

The connective tissue

sutures.

at immobile joints called

The skull is composed of several separate bones united

Composition

and

diploë

optic canal

lacrimal

frontal

zygomaticomaxillar

superciliary arch

nasal

frontal process
of maxilla

supraorbital notch

parietal

greater wing
of sphenoid

zygomatic process
of frontal

squamous temporal

zygomatic

infraorbital foramen

mastoid process

ramus of mandible

body of mandible

symphysis menti

mental foramen

maxilla

inferior concha

middle concha

suture

inferior orbital

fissure

superior orbital

fissure

zygomatic

frontozygomatic

suture

coronal suture

orbital plate of frontal

FIGURE 11.1

Bones of the anterior aspect of the skull.

530

CHAPTER 11

The Head and Neck

superficial vein of scalp

emissary vein

cerebral artery in

skin

connective tissue

aponeurosis

loose connective

tissue

pericranium

(periosteum)

outer table of

parietal bone

diploe

inner table of

parietal bone

cerebral vein in

subarachnoid space

cerebral cortex

pia mater

subarachnoid space

arachnoid

meningeal layer

of dura mater

endosteal layer

of dura mater

arachnoid granulation

superior sagittal sinus

diploic vein

sagittal suture

falx cerebri

inferior sagittal sinus

FIGURE 11.2

tal suture of the skull,

Coronal section of the upper part of the head showing the layers of the scalp, the sagit

and serves as a voice resonator.

This communicates with the nasal cavity

maxillary sinus.

mid-shaped cavity lined with mucous membrane called the

carries the upper teeth. Within each maxilla is a large, pyra

which

alveolar arch,

fellow of the opposite side, forms the

projects downward and, together with the

alveolar process

The

infraorbital foramen.

the maxilla is perforated by the

the lower margin of the nasal aperture. Below the orbit,

and form

intermaxillary suture

meet in the midline at the

and part of the floors of the orbital cavities. The two bones

the hard palate, part of the lateral walls of the nasal cavities,

form the upper jaw, the anterior part of

maxillae

The two

are separate bones.

inferior conchae

on each side; the

ethmoid

ject into the nasal cavity from the

are shelves of bone that pro

middle conchae

superior

The

vomer.

nasal septum, which is largely formed by the

The nasal cavity is divided into two by the bony

aperture.

anterior nasal

lower borders, with the maxillae, make the

form the bridge of the nose. Their

two nasal bones

The

and serve as voice resonators.

These communicate with the nose

frontal air sinuses.

are two hollow spaces lined with mucous membrane called

just above the orbital margins,

frontal bone,

Within the

medially.

riorly, and the processes of the maxilla and frontal bone

superiorly, the zygomatic bone laterally, the maxilla infe

are bounded by the frontal bone

orbital margins

The

tal bone articulates with the zygomatic bone.

of the maxillae and with the nasal bones. Laterally, the fron

ally, the frontal bone articulates with the frontal processes

can be recognized. Medi

foramen,

supraorbital notch,

can be seen on either side, and the

superciliary arches

The

to make the upper margins of the orbits (Fig. 11.1).

or forehead bone, curves downward

frontal bone,

The

Anterior View of the Skull

External Views of the Skull

the following description.

should have a dried skull available for reference as they read

students should be familiar with the skull as a whole and

detailed structure of each individual skull bone. However,

It is unnecessary for students of medicine to know the

Mandible: 1

Inferior conchae: 2

Palatine bones: 2

Vomer: 1

Lacrimal bones: 2

Nasal bones: 2

Maxillae: 2

Zygomatic bones: 2

single:

consist of the following, two of which are

facial bones

The

Ethmoid bone: 1

Sphenoid bone: 1

Temporal bones: 2

Occipital bone: 1

Parietal bones: 2

Frontal bone: 1

which are paired (Figs. 11.3 and 11.4):

consists of the following bones, two of

cranium

The

relation of cerebral blood vessels to the subarachnoid space.

the falx cerebri, the superior and inferior sagittal venous sinuses, the arachnoid granulations, the emissary veins, and the

■

the

and

Basic Anatomy

531

external auditory meatus

squamous temporal

zygoma

pterion

coronal suture

temporal lines

frontal

greater wing

of sphenoid

zygomatic process

of frontal

nasion

frontal process

of zygomatic

lacrimal

zygomatic

zygomaticofacial

foramen

infraorbital foramen

coronoid process

maxilla

alveolar part

mental foramen

body of mandible

ramus

angle

neck of mandible

head of mandible

styloid process

mastoid process

tympanic plate

suprameatal spine

suprameatal triangle

superior nuchal line

external occipital

protuberance (inion)

occipital

lambdoid

suture

supramastoid crest

parietal

nasal

FIGURE 11.3

Bones of the lateral aspect of the skull.

sagittal suture

occipital

parietomastoid
suture

mandible

styloid process

mastoid process

superior nuchal
line

external occipital
protuberance

lambdoid suture

inferior temporal
line

superior temporal
line

parietal

nasal

frontal

coronal
suture

sagittal
suture

parietal

lambdoid
suture

FIGURE 11.4

Bones of the skull viewed from the posterior (A) and superior (B) aspects.

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CHAPTER 11

infratemporal fossa through the pterygomaxillary fissure,

below the orbital cavity. It communicates laterally with the

is a small space behind and

pterygopalatine fossa

The

maxilla. It leads forward into the orbit.

between the greater wing of the sphenoid bone and the

is a horizontal fissure

inferior orbital fissure

The

palatine fossa.

pterygo

and back of the maxilla. It leads medially into the

fossa between the pterygoid process of the sphenoid bone

is a vertical fissure that lies within the

gomaxillary fissure

ptery

on the greater wing of the sphenoid. The

ral crest

infratempo

lies below the

infratemporal fossa

The

rior temporal line.

lies below the infe

temporal fossa

they arch backward. The

the zygomatic process of the frontal bone and diverge as

which begin as a single line from the posterior margin of

inferior temporal lines,

superior

Identify the

vein.

artery

middle meningeal

it overlies the anterior division of the

Clinically, the pterion is an important area because

pterion.

is referred to as the

articulates with the greater wing of the sphenoid; this point

skull is where the anteroinferior corner of the parietal bone

Note that the thinnest part of the lateral wall of the

tus. The ramus and body of the mandible lie inferiorly.

Note the position of the external auditory mea

sphenoid.

greater wing of the

zygomatic process;

cess,

squamous, tympanic, mastoid process, styloid pro

namely,

temporal bone,

parts of the

occipital bone;

of the

The skull is completed at the side by the squamous part

lambdoid suture.

behind, at the

They articulate with the occipital bone

sagittal suture.

nium and articulate with each other in the midline at the

form the sides and roof of the cra

parietal bones

The

suture (Fig. 11.3).

skull and articulates with the parietal bone at the coronal

forms the anterior part of the side of the

frontal bone

The

Lateral View of the Skull

body and two vertical rami (for details, see page 569).

or lower jaw, consists of a horizontal

mandible,

The

otemporal nerves.

by two foramina for the zygomaticofacial and zygomatic

form the zygomatic arch. The zygomatic bone is perforated

ulates with the zygomatic process of the temporal bone to

Medially, it articulates with the maxilla and laterally it artic

and part of the lateral wall and floor of the orbital cavity.

forms the prominence of the cheek

zygomatic bone

The

The Head and Neck

the

and

and the

and

medially with the nasal cavity through the

rotundum, and anteriorly with the orbit through the

superiorly with the skull through the foramen

foramen,

sphenopalatine

Above the posterior edge of the hard palate are the

foramina.

lesser palatine

greater

Posterolaterally are the

men.

fora

incisive fossa

In the midline anteriorly is the

can be identified.

zontal plates of the palatine bones

hori

palatal processes of the maxillae

The

(Fig. 11.5).

hard palate

the skull is seen to be formed by the

If the mandible is discarded, the anterior part of this aspect of

Inferior View of the Skull

sagittal suture.

in the midline at the

Behind, the two parietal bones articulate

metopic suture.

two halves of the frontal bone fail to fuse, leaving a midline

Occasionally, the

coronal suture.

two parietal bones at the

Anteriorly, the frontal bone (Fig. 11.4) articulates with the

Superior View of the Skull

extend laterally toward the temporal bone.

superior nuchal lines

either side of the protuberance the

attachment to muscles and the ligamentum nuchae. On

which gives

external occipital protuberance,

called the

the midline of the occipital bone is a roughened elevation

the occipital bone articulates with the temporal bone. In

On each side

lambdoid suture.

the occipital bone at the

the parietal bones articulate with the squamous part of

are seen above. Below,

sagittal suture

with the intervening

The posterior parts of the two parietal bones (Fig. 11.4)

Posterior View of the Skull

inferior orbital fissure.

and the

and

on the lateral surface of

suprameatal crest

identify the

While examining this region,

external auditory meatus.

bone, is C shaped on section and forms the bony part of the

which forms part of the temporal

tympanic plate,

The

this foramen from the cavity of the skull to the exterior.

with fibrous tissue, and only a few small vessels pass through

During life, the foramen lacerum is closed

men lacerum.

fora

bone and the greater wing of the sphenoid, forms the

is irregular and, together with the basilar part of the occipital

The medial end of the petrous part of the temporal bone

of the petrous part of the temporal bone.

can be seen on the inferior surface

carotid canal

ing of the

downward and forward from its inferior aspect. The open

of the temporal bone projects

styloid process

The

tympani nerve exits from the tympanic cavity.

through the medial end of which the chorda

panic fissure,

squamotym

from the tympanic plate posteriorly is the

temporomandibular joint. Separating the mandibular fossa

form the upper articular surfaces for the

articular tubercle

of the temporal bone and the

mandibular fossa

The

can be identified.

The opening of the bony part of the tube

auditory tube.

temporal bone, is a groove for the cartilaginous part of the

the greater wing of the sphenoid and the petrous part of the

Behind the spine of the sphenoid, in the interval between

spine of the sphenoid.

foramen spinosum is the

Posterolateral to the

foramen spinosum.

and the small

foramen ovale

wing of the sphenoid is pierced by the large

the greater

lateral pterygoid plate,

Posterolateral to the

hamulus.

pterygoid

is prolonged as a curved spike of bone, the

plate

medial pterygoid

sphenoid bone. The inferior end of the

of the

medial pterygoid plates

are bounded laterally by the

and

vomer

from each other by the posterior margin of the

(posterior nasal apertures). These are separated

choanae

Basic Anatomy

533

incisive foramen

palatal process of palatine

inferior orbital fissure

greater palatine foramen

lesser palatine foramen

vomer

lateral pterygoid

plate

medial pterygoid

plate

foramen ovale
foramen spinosum

spine of sphenoid

petrous part of
temporal bone

tympanic part of

temporal bone

carotid canal

jugular foramen

condyle

external occipital protuberance

occipital bone

superior nuchal line

foramen magnum

pharyngeal tubercle

mastoid process

stylomastoid

foramen

squamous part of

temporal bone

styloid process

articular tubercle

mandibular fossa

scaphoid fossa

infratemporal crest

hamulus

tubercle of maxilla

zygomatic arch

palatal process of maxilla

hypoglossal canal

FIGURE 11.5

Inferior surface of the base of the skull.

suprameatal

the squamous part of the temporal bone, the

triangle,

In the interval between the styloid and mastoid

suprameatal spine.

and the

processes, the

a shallower notch on the occipital bone, forms the

temporal bone has a deep notch, which, together with

Medial to the styloid process, the petrous part of the

can be seen.

stylomastoid foramen

side.

lines should be identified as they curve laterally on each

the external occipital protuberance. The superior nuchal

Posterior to the foramen magnum in the midline is

sal nerve (Fig. 11.6).

for transmission of the hypoglos

hypoglossal canal

cervical vertebra, the atlas. Superior to the occipital condyle

late with the superior aspect of the lateral mass of the first

should be identified; they articu

occipital condyles

The

part of the occipital bone in the midline.

is a small prominence on the undersurface of the basilar

pharyngeal tubercle

basilar part of the occipital bone. The

of the foramen magnum are the sphenoid bone and the

Behind the posterior apertures of the nose and in front

jugular foramen.

is the

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CHAPTER 11

The Head and Neck

crista galli

foramen cecum

cribriform plate

orbital plate of frontal

optic canal

anterior clinoid process

foramen rotundum
foramen lacerum

foramen ovale

groove for middle

meningeal artery

foramen spinosum

squamous part

of temporal

internal acoustic
meatus

groove for

sigmoid sinus

groove for transverse sinus

hypoglossal canal

internal occipital protuberance

internal occipital crest

foramen magnum

basilar part of occipital

jugular foramen

groove for superior

petrosal sinus

arcuate eminence

hiatus for

greater

petrosal nerve

dorsum sellae

posterior

clinoid process

sella turcica

tuberculum sellae

lesser wing of sphenoid

petrous part

of temporal

FIGURE 11.6

Internal surface of the base of the skull.

cerebral hemispheres. It is bounded anteriorly by the inner

The anterior cranial fossa lodges the frontal lobes of the

Anterior Cranial Fossa

the petrous part of the temporal bone.

cranial fossa is separated from the posterior cranial fossa by

nial fossa by the lesser wing of the sphenoid, and the middle

The anterior cranial fossa is separated from the middle cra

into three cranial fossae: anterior, middle, and posterior.

The interior of the base of the skull (Fig. 11.6) is divided

the vault.

as they pass up the side of the skull to

meningeal vessels

middle

sent for the anterior and posterior divisions of the

(see page 543). Several narrow grooves are pre

ulations

arachnoid gran

lateral lacunae

which lodge the

granular

side of the groove are several small pits, called

On each

superior sagittal sinus.

tal groove that lodges the

tal, and lambdoid sutures. In the midline is a shallow sagit

The internal surface of the vault shows the coronal, sagit

Vault of the Skull

and venous sinuses.

meninges, portions of the cranial nerves, arteries, veins,

The cranial cavity contains the brain and its surrounding

The Cranial Cavity

-
-

pits,

and

-
-

Base of the Skull

surface of the frontal bone, and in the midline is a crest for

angle of the parietal bone, or the pterion. The medial end of

laterally with the frontal bone and meets the anteroinferior

is the sharp lesser wing of the sphenoid, which articulates

Its posterior boundary

falx cerebri.

the attachment of the

Basic Anatomy

the apex of the petrous part of the temporal bone for the

Lateral to the foramen lacerum is an impression on

cess, and emerges from the cavernous sinus (see page 598).

cally upward, medial (Fig. 11.20) to the anterior clinoid pro

process. At this point, the internal carotid artery turns verti

cavernous sinus to reach the region of the anterior clinoid

of the sphenoid bone. Here, the artery turns forward in the

and immediately turns upward to reach the side of the body

carotid artery enters the foramen through the carotid canal

lacerum above the closed inferior opening. The internal

opens into the side of the foramen

carotid canal

The

from the cranial cavity to the neck.

tissue, and only small blood vessels pass through this tissue

the foramen lacerum in life is filled by cartilage and fibrous

and the sphenoid bone (Fig. 11.6). The inferior opening of

between the apex of the petrous part of the temporal bone

foramen lacerum

The large and irregularly shaped

mous part of the temporal bone to reach the parietal bone.

terior branch passes backward and upward across the squa

may be damaged after a blow to the side of the head. The pos

upward on the parietal bone. It is at this site that the artery

by the artery for a short distance before it runs backward and

(Fig. 11.131A). Here, the bone is deeply grooved or tunneled

and upward to the anteroinferior angle of the parietal bone

and posterior branches. The anterior branch passes forward

11.20). After a short distance, the artery divides into anterior

temporal bone and the greater wing of the sphenoid (Fig.

a groove on the upper surface of the squamous part of the

cranial cavity. The artery then runs forward and laterally in

artery from the infratemporal fossa (see page 598) into the

sphenoid. The foramen transmits the middle meningeal

foramen ovale and also perforates the greater wing of the

lies posterolateral to the

foramen spinosum

The small

fossa; the lesser petrosal nerve also passes through it.

motor root of the mandibular nerve to the infratemporal

sphenoid and transmits the large sensory root and small

rotundum (Fig. 11.6). It perforates the greater wing of the

lies posterolateral to the foramen

foramen ovale

The

the trigeminal ganglion to the pterygopalatine fossa.

wing of the sphenoid and transmits the maxillary nerve from

medial end of the superior orbital fissure, perforates the greater

which is situated behind the

foramen rotundum,

The

wing of the sphenoid and drains into the cavernous sinus.

sinus runs medially along the posterior border of the lesser

the superior ophthalmic vein. The sphenoparietal venous

lomotor, nasociliary, and abducent nerves, together with

the sphenoid, transmits the lacrimal, frontal, trochlear, ocu

slitlike opening between the lesser and the greater wings of

which is a

superior orbital fissure,

artery, to the orbit. The

and the ophthalmic artery, a branch of the internal carotid

transmits the optic nerve

optic canal

Anteriorly, the

serve as voice resonators.

membrane and communicate with the nasal cavity; they

which are lined with mucous

sphenoid air sinuses,

stretched on each side. The body of the sphenoid contains

that are out

lesser wings

and

greater

with

body

placed

The sphenoid bone resembles a bat having a centrally

mous and petrous parts of the temporal bone.

is formed by the greater wing of the sphenoid and the squa

The floor of each lateral part of the middle cranial fossa

noid, and the parietal bones.

parts of the temporal bones, the greater wings of the sphe

parts of the temporal bones. Laterally lie the squamous

noid and posteriorly by the superior borders of the petrous

It is bounded anteriorly by the lesser wings of the sphe

cerebral hemispheres.

of the

temporal lobes

lateral parts form concavities on either side, which lodge

is formed by the body of the sphenoid, and the expanded

expanded lateral parts (Fig. 11.6). The median raised part

The middle cranial fossa consists of a small median part and

Middle Cranial Fossa

olfactory nerves.

cribriform plate are for the

ports the olfactory bulbs, and the small perforations in the

cavity. The upper surface of the cribriform plate sup

into the nasal

anterior ethmoidal nerve

the passage of the

the crista galli is a narrow slit in the cribriform plate for

midline for the attachment of the falx cerebri. Alongside

is a sharp upward projection of the ethmoid bone in the

crista galli

of the ethmoid medially (Fig. 11.6). The

plate

cribriform

plates of the frontal bone laterally and by the

The floor of the fossa is formed by the ridged orbital

is limited posteriorly by the groove for the optic chiasma.

The median part of the anterior cranial fossa

rium cerebelli.

tento

on each side, which gives attachment to the

process

anterior clinoid

the lesser wing of the sphenoid forms the

535

the

-
-

lies

-
-

body of the sphenoid (Figs. 11.9 and 11.10). It carries in its

The cavernous sinus is directly related to the side of the

attachment to the fixed margin of the tentorium cerebelli.

which give

posterior clinoid processes,

tubercles, called the

The superior angles of the dorsum sellae have two

sellae.

dorsum

posteriorly by a square plate of bone called the

The sella turcica is bounded

pituitary gland.

lodges the

which

sella turcica,

the elevation is a deep depression, the

Behind

tuberculum sellae.

to the sulcus is an elevation, the

on each side. Posterior

optic canal

and leads laterally to the

which is related to the optic chiasma

sulcus chiasmatis,

by the body of the sphenoid bone (Fig. 11.6). In front is

The median part of the middle cranial fossa is formed

hemisphere (Fig. 11.30).

the tympanic cavity from the temporal lobe of the cerebral

of bone is the only major barrier that separates infection in

the tympanic cavity, and the auditory tube. This thin plate

behind forward, it forms the roof of the mastoid antrum,

adjoins the squamous part of the bone (Fig. 11.6). From

extension of the petrous part of the temporal bone and

a thin plate of bone, is a forward

tegmen tympani,

The

superior semicircular canal.

the underlying

the anterior surface of the petrous bone and is caused by

is a rounded eminence found on

arcuate eminence

The

the cavernous sinus.

glion. Here, it leaves the posterior cranial fossa and enters

apex of the petrous bone, medial to the trigeminal gan

The abducent nerve bends sharply forward across the

ward to the foramen ovale.

The lesser petrosal nerve passes for

the pterygoid canal.

nerve of

around the internal carotid artery), to form the

(sympathetic fibers from

deep petrosal nerve

and joins the

enters the foramen lacerum deep to the trigeminal ganglion

branch of the tympanic plexus. The greater petrosal nerve

lesser petrosal nerve,

the smaller lateral groove is for the

a branch of the facial nerve;

greater petrosal nerve,

for the

bone are two grooves for nerves; the largest medial groove is

On the anterior surface of the petrous

trigeminal ganglion.

the

536

CHAPTER 11

and the large

11th cranial nerves;

and

9th, 10th,

inferior petrosal sinus;

tures from before backward: the

part of the occipital bone. It transmits the following struc

the petrous part of the temporal bone and the condylar

lies between the lower border of

jugular foramen

The

hypoglossal nerve.

transmits the

eral boundary of the foramen magnum (Fig. 11.6) and

is situated above the anterolat

hypoglossal canal

The

sory nerves, and the two vertebral arteries.

rounding meninges, the ascending spinal parts of the acces

floor and transmits the medulla oblongata and its sur

occupies the central area of the

foramen magnum

The

above (Fig. 11.10).

below and the occipital lobes of the cerebral hemispheres

which intervenes between the cerebellum

torium cerebelli,

ten

The roof of the fossa is formed by a fold of dura, the

of the temporal bone.

squamous parts of the occipital bone and the mastoid part

the posterior fossa is formed by the basilar, condylar, and

mous part of the occipital bone (Fig. 11.6). The floor of

teriorly it is bounded by the internal surface of the squa

border of the petrous part of the temporal bone, and pos

Anteriorly, the fossa is bounded by the superior

oblongata.

medulla

cerebellum, pons,

the hindbrain, namely, the

The posterior cranial fossa is deep and lodges the parts of

Posterior Cranial Fossa

nerve pass forward through the sinus.

(Fig. 11.12). The internal carotid artery and the 6th cranial

thalmic and maxillary divisions of the 5th cranial nerve

lateral wall the 3rd and 4th cranial nerves and the oph

The Head and Neck

and

-
-

the

to it is attached the small

nal occipital protuberance;

inter

line posteriorly from the foramen magnum to the

runs upward in the mid

internal occipital crest

The

roots of the facial nerve.

the vestibulocochlear nerve and the motor and sensory

face of the petrous part of the temporal bone. It transmits

pierces the posterior sur

internal acoustic meatus

The

jugular vein.

internal

turns down through the foramen to become the

temporal bone to reach the foramen. The sigmoid sinus

the groove on the lower border of the petrous part of the

The inferior petrosal sinus descends in

sigmoid sinus.

falx

cerebelli

pass through them.

openings in the base of the skull and the structures that

Table 11.1 provides a summary of the more important

rior to the mastoid antrum.

toid part of the temporal bone. Here, it lies directly poste

deeply grooves the back of the petrous bone and the mas

As the sigmoid sinus descends to the jugular foramen, it

bone in a narrow groove and drains into the sigmoid sinus.

runs backward along the upper border of the petrous

sinus

superior petrosal

The

sigmoid sinus.

sinus becomes the

mastoid part of the temporal bone, and here the transverse

corner of the parietal bone. The groove now passes onto the

of the occipital bone, to reach the posteroinferior angle or

groove sweeps around on either side, on the internal surface

(Fig. 11.6). This

transverse sinus

a wide groove for the

On each side of the internal occipital protuberance is

occipital sinus.

over the

-
-

Summary of the More Important Openings in the Base of the Skull and the

Structures That Pass Through Them

T A B L E 1 1 . 1

Vestibulocochlear and facial nerves

Lacrimal, frontal, trochlear, oculomotor, nasociliary,

Structures Transmitted

Opening in Skull

Bone of Skull

Anterior Cranial Fossa
Perforations in cribriform plate

Ethmoid

Olfactory nerves

Middle Cranial Fossa
Optic canal

Lesser wing of sphenoid

Optic nerve, ophthalmic artery

Superior orbital fissure

Between lesser and greater

wings of sphenoid

and abducent nerves; superior ophthalmic vein

Foramen rotundum

Greater wing of sphenoid

Maxillary division of the trigeminal nerve

Foramen ovale

Greater wing of sphenoid

Mandibular division of the trigeminal nerve,

lesser petrosal nerve

Foramen spinosum

Greater wing of sphenoid

Middle meningeal artery

Foramen lacerum

Between petrous part of temporal

and sphenoid

Internal carotid artery

Posterior Cranial Fossa
Foramen magnum

Occipital

Medulla oblongata, spinal part of accessory nerve,

and right and left vertebral arteries

Hypoglossal canal

Occipital

Hypoglossal nerve

Jugular foramen

Between petrous part of temporal

and condylar part of occipital

Glossopharyngeal, vagus, and accessory nerves;

sigmoid sinus becomes internal jugular vein

Internal acoustic m

eatus

Petrous part of temporal

Basic Anatomy

537

Fractures of the Skull

bital nerve with anesthesia or paresthesia of the skin of the cheek

riform plate of the ethmoid bone. Double vision (diplopia) may be

with anterior open bite, and possibly leakage of cerebrospinal

ity of the underlying bone on palpation, malocclusion of the teeth

Maxillofacial fractures usually occur as the result of massive

cartilage); therefore, this part of the skull in children is relatively

facial fractures. Fortunately, the upper part of the skull is devel

biotic therapy.

the presence of well-developed, air-filled sinuses and the muco

adult’s, and fractures may be incomplete or greenstick. In adults,

The developing bones of a child’s face are more pliable than an

nerve from injury.

10th, and 11th cranial nerves may be damaged. The strong bony

days later, it tracks between the muscles and appears in the pos

brospinal fluid may leak into the sphenoidal air sinuses and then

bone. The 3rd, 4th, and 6th cranial nerves may be damaged if

involved as they pass through the petrous part of the temporal

tory meatus is common. The 7th and 8th cranial nerves may be

ina and canals in this region; the cavities of the middle ear and

this is the weakest part of the base of the skull. Anatomically,

Fractures of the middle cranial fossa are common, because

hemorrhage beneath the conjunctiva and into the orbital cavity,

of the overlying meninges and underlying mucoperiosteum. The

ball in that a localized blow produces a depression without splin

to the vault often result in a series of linear fractures, which radi

which it splinters. A severe, localized blow produces a local

brittle. Moreover, the sutural ligaments begin to ossify during

Fractures of the skull are common in the adult but much less so

in the young child. In the infant skull, the bones are more resilient

than in the adult skull, and they are separated by fibrous sutural

ligaments. In the adult, the inner table of the skull is particularly

middle age.

The type of fracture that occurs in the skull depends on the

age of the patient, the severity of the blow, and the area of skull

receiving the trauma. The adult skull may be likened to an egg-

shell in that it possesses a certain limited resilience beyond

indentation, often accompanied by splintering of the bone. Blows

ate out through the thin areas of bone. The petrous parts of the

temporal bones and the occipital crests strongly reinforce the

base of the skull and tend to deflect linear fractures.

In the young child, the skull may be likened to a table-tennis

tering. This common type of circumscribed lesion is referred to

as a “pond” fracture.

Fractures of the Anterior Cranial Fossa
In fractures of the anterior cranial fossa, the cribriform plate of

the ethmoid bone may be damaged. This usually results in tearing

patient will have bleeding from the nose (epistaxis) and leakage

of cerebrospinal fluid into the nose (cerebrospinal rhinorrhea).

Fractures involving the orbital plate of the frontal bone result in

causing exophthalmos. The frontal air sinus may be involved,

with hemorrhage into the nose.

Fractures of the Middle Cranial Fossa

this weakness is caused by the presence of numerous foram-

the sphenoidal air sinuses are particularly vulnerable. The leak-

age of cerebrospinal fluid and blood from the external audi-

the lateral wall of the cavernous sinus is torn. Blood and cere-

into the nose.

Fractures of the Posterior Cranial Fossa
In fractures of the posterior cranial fossa, blood may escape into

the nape of the neck deep to the postvertebral muscles. Some

terior triangle, close to the mastoid process. The mucous mem-

brane of the roof of the nasopharynx may be torn, and blood may

escape there. In fractures involving the jugular foramen, the 9th,

walls of the hypoglossal canal usually protect the hypoglossal

Fractures of Facial Bones

Bone Injuries and Skeletal Development

periosteal surfaces of the alveolar parts of the upper and lower

jaws means that most facial fractures should be considered to

be open fractures, susceptible to infection, and requiring anti-

Anatomy of Common Facial Fractures
Automobile accidents, fisticuffs, and falls are common causes of

oped from membrane (whereas the remainder is developed from

flexible and can absorb considerable force without resulting in

a fracture.

Signs of fractures of the facial bones include deformity, ocu-

lar displacement, or abnormal movement accompanied by crepi-

tation and malocclusion of the teeth. Anesthesia or paresthesia

of the facial skin will follow fracture of bones through which

branches of the trigeminal nerve pass to the skin.

The muscles of the face are thin and weak and cause little

displacement of the bone fragments. Once a fracture of the

maxilla has been reduced, for example, prolonged fixation is

not needed. However, in the case of the mandible, the strong

muscles of mastication can create considerable displacement,

requiring long periods of fixation.

The most common facial fractures involve the nasal bones,

followed by the zygomatic bone and then the mandible. To frac-

ture the maxillary bones and the supraorbital ridges of the frontal

bones, an enormous force is required.

Nasal Fractures
Fractures of the nasal bones, because of the prominence of the

nose, are the most common facial fractures. Because the bones

are lined with mucoperiosteum, the fracture is considered open;

the overlying skin may also be lacerated. Although most are sim-

ple fractures and are reduced under local anesthesia, some are

associated with severe injuries to the nasal septum and require

careful treatment under general anesthesia.

Maxillofacial Fractures

facial trauma. There is extensive facial swelling, midface mobil-

fluid (cerebrospinal rhinorrhea) secondary to fracture of the crib-

present, owing to orbital wall damage. Involvement of the infraor-

and upper gum may occur in fractures of the body of the maxilla.

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

(continued)

538

CHAPTER 11

The Head and Neck

Nose bleeding may also occur in maxillary fractures. Blood

can no longer be palpated.

the end of the 1st year, the fontanelle is usually closed and

parietal bones in front and the occipital bone behind. By

is triangular and lies between the two

posterior fontanelle

replaced by bone and is closed by 18 months of age. The

membrane forming the floor of the anterior fontanelle is

the two parietal bones behind (Fig. 11.8). The fibrous

between the two halves of the frontal bone in front and

is diamond shaped and lies

anterior fontanelle

The

midline of the vault.

nelles are most important and are easily examined in the

Clinically, the anterior and posterior fonta

fontanelles.

are separated by unossified membranous intervals called

the vault are not closely knit at sutures, as in the adult, but

the bones of the base are ossified in cartilage. The bones of

cartilage. The bones of the vault are ossified in membrane;

mobile on each other, being connected by fibrous tissue or

at birth, but the process is incomplete, and the bones are

being no diploë present. Most of the skull bones are ossified

The bones of the skull are smooth and unilaminar, there

results in a great increase in length of the face.

illary sinuses, and the alveolar processes of the maxillae

face. In childhood, the growth of the mandible, the max

skull, has a disproportionately large cranium relative to the

The newborn skull (Fig. 11.8), compared with the adult

tents of the orbital cavity to explode downward through the floor

enters the maxillary air sinus and then leaks into the nasal cavity.

The sites of the fractures were classified by Le Fort as type I,

II, or III; these fractures are summarized in Figure 11.7.

Blowout Fractures of the Maxilla

A severe blow to the orbit (as from a baseball) may cause the con-

of the orbit into the maxillary sinus. Damage to the infraorbital

nerve, resulting in altered sensation to the skin of the cheek,

upper lip, and gum, may occur.

Fractures of the Zygoma or Zygomatic Arch
The zygoma or zygomatic arch can be fractured by a blow to the

side of the face. Although it can occur as an isolated fracture,

as from a blow from a clenched fist, it may be associated with

multiple other fractures of the face, as often seen in automobile

accidents.

Neonatal Skull

Le Fort I

Le Fort II

Le Fort III

FIGURE 11.7

Le Fort classification of maxillofacial fractures.

head is bent posteriorly.

smaller, the ramus becomes oblique in position so that the

the teeth are lost. As the alveolar part of the bone becomes

In old age, the size of the mandible is reduced when

than the coronoid process.

the head and neck grow so that the head comes to lie higher

that the angle of the mandible assumes the adult shape and

the head. It is only after eruption of the permanent teeth

body and the coronoid process lying at a superior level to

the head being placed level with the upper margin of the

at birth is obtuse (Fig. 11.8),

angle of the mandible

The

by the end of the 1st year.

symphysis menti

the midline with fibrous tissue. The two halves fuse at the

The mandible has right and left halves at birth, united in

surface.

puberty the antrum may lie as much as 15 mm from the

skull continues, the lateral bony wall thickens so that at

As growth of the

suprameatal triangle.

the floor of the

At birth, the mastoid antrum lies about 3 mm deep to

omastoid muscle when the child moves his or her head.

and develops later in response to the pull of the sternocleid

is not present at birth (Fig. 11.8)

mastoid process

The

tympanic membrane comes to face more directly laterally.

grows laterally, forming the bony part of the meatus, and the

faces more inferiorly. During childhood, the tympanic plate

the tympanic membrane is nearly as large as in the adult, it

is nearer the surface. Although

tympanic membrane

meatus is almost entirely cartilaginous in the newborn, and

plate in the adult. This means that the external auditory

C-shaped ring at birth, compared with a C-shaped curved

is merely a

tympanic part of the temporal bone

The

The red line denotes the fracture line.

the

Clinical Features of the Neonatal Skull

state of the intracranial pressure (a bulging fontanelle indi

Fontanelles
Palpation of the fontanelles enables the physician to deter-

mine the progress of growth in the surrounding bones, the

degree of hydration of the baby (e.g., if the fontanelles are

depressed below the surface, the baby is dehydrated), and the

cates raised intracranial pressure).

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

(continued)

Basic Anatomy

539

Samples of cerebrospinal fluid can be obtained by passing

men, is close to the surface. Thus, it can be damaged by for

and the facial nerve, as it emerges from the stylomastoid fora

fontanelle after 18 months, because the frontal and parietal

a long needle obliquely through the anterior fontanelle into the

subarachnoid space or even into the lateral ventricle.

Clinically, it is usually not possible to palpate the anterior

bones have enlarged to close the gap.

Tympanic Membrane
At birth, the tympanic membrane faces more downward and

less laterally than in maturity; when examined with the oto-

scope, it therefore lies more obliquely in the infant than in the

adult.

Forceps Delivery and the Facial Nerve
In the newborn infant, the mastoid process is not developed,

ceps in a difficult delivery.

anterior fontanelle

frontal
suture

intermaxillary
suture

mandible

symphysis menti

anterior fontanelle

mandible

tympanic part of temporal bone

tympanic membrane

stylomastoid foramen

posterior
fontanelle

parietal
eminence

FIGURE 11.8

Neonatal skull as seen from the anterior

The brain in the skull is surrounded by three protective

(A) and lateral (B) aspects.

The Meninges

membranes, or meninges: the dura mater, the arachnoid
mater, and the pia mater. (The spinal cord in the vertebral
column is also surrounded by three meninges. See page 699.)

lateral wall of the cavernous sinus (Figs. 11.11 and 11.12).

the third and fourth cranial nerves pass forward to enter the

cess on each side. At the point where the two borders cross,

the attached border, and is affixed to the anterior clinoid pro

bone. The free border runs forward at its two ends, crosses

of the grooves for the transverse sinuses on the occipital

the superior borders of the petrous bones, and the margins

fixed border is attached to the posterior clinoid processes,

inner free border and an outer attached or fixed border. The

of the midbrain (Figs. 11.11 and 11.12), thus producing an

for the passage

tentorial notch,

spheres. In front is a gap, the

lum and supports the occipital lobes of the cerebral hemi

11.10, and 11.11). It covers the upper surface of the cerebel

mater that roofs over the posterior cranial fossa (Figs. 11.9,

is a crescent-shaped fold of dura

tentorium cerebelli

The

sinus runs along its attachment to the tentorium cerebelli.

sinus runs in its lower concave free margin, and the straight

sinus runs in its upper fixed margin, the inferior sagittal

surface of the tentorium cerebelli. The superior sagittal

broad posterior part blends in the midline with the upper

attached to the internal frontal crest and the crista galli. Its

spheres (Figs. 11.9 and 11.13). Its narrow end in front is

that lies in the midline between the two cerebral hemi

is a sickle-shaped fold of dura mater

falx cerebri

The

to restrict the rotatory displacement of the brain.

the subdivisions of the brain. The function of these septa is

the cranial cavity into freely communicating spaces lodging

The meningeal layer sends inward four septa that divide

rium of the nerves.

skull. Outside the skull, the sheaths fuse with the epineu

cranial nerves as the latter pass through the foramina in the

mater of the spinal cord. It provides tubular sheaths for the

continuous through the foramen magnum with the dura

dense, strong, fibrous membrane covering the brain and is

is the dura mater proper. It is a

meningeal layer

The

base of the skull.

ments. It is most strongly adherent to the bones over the

bones. At the sutures, it is continuous with the sutural liga

continuous with the periosteum on the outside of the skull

the margins of all the foramina in the skull, it becomes

continuous with the dura mater of the spinal cord. Around

through the foramen magnum to become

does not extend

periosteum covering the inner surface of the skull bones.

is nothing more than the ordinary

endosteal layer

The

they separate to form venous sinuses.

These are closely united except along certain lines, where

the endosteal layer and the meningeal layer (Fig. 11.2).

The dura mater is conventionally described as two layers:

Dura Mater of the Brain

-
-

540

CHAPTER 11

The Head and Neck

superficial vein of scalp

emissary vein

diploic vein

cerebral vein

left transverse sinus

great cerebral vein

falx cerebri

confluence

of sinuses

straight sinus

tentorium cerebelli

right transverse sinus

sigmoid sinus

superior petrosal sinus

facial vein

ophthalmic vein

cavernous sinus

sphenoparietal
sinus

intercavernous sinuses

oculomotor nerve

trochlear nerve

trigeminal nerve

facial and
vestibulocochlear
nerves

diploe

inferior sagittal sinus

superior sagittal sinus

olfactory bulb

FIGURE 11.9

Interior of the skull showing the dura mater and its contained venous sinuses. Note the connections of the

veins of the scalp and the veins of the face with the venous sinuses.

intercavernous sinuses

diaphragma sellae

oculomotor nerve

trochlear nerve

abducent nerve

foramen magnum

superior

petrosal sinus

sigmoid sinus

tentorial notch

left transverse sinus

great cerebral vein

confluence of sinuses

straight sinus

right transverse sinus

inferior sagittal

sinus

tentorium
cerebelli

mandibular nerve

trigeminal ganglion

maxillary nerve

cavernous sinus

infundibulum

optic nerve

FIGURE 11.10

Diaphragma sellae and tentorium cerebelli. Note the position of the venous sinuses.

Basic Anatomy

541

tentorium cerebelli

midbrain (sectioned)

cerebral aqueduct

trochlear
nerve

internal
carotid
artery

trigeminal
nerve

cut margin of

meningeal layer of

dura

greater superficial

petrosal nerve

mandibular division of

trigeminal nerve

trigeminal
ganglion

maxillary division of
trigeminal nerve

trochlear nerve

internal carotid artery

right optic nerve

olfactory bulb

frontal sinus

optic chiasma

infundibulum

posterior communicating artery

posterior cerebral artery

inferior sagittal sinus (cut open)

falx cerebri

abducent nerve

internal carotid artery

oculomotor nerve

FIGURE 11.11

Lateral view of the skull showing the falx cerebri, tentorium cerebelli, brainstem, and trigeminal ganglion.

supplies the posterior part of the dura mater.

brain. The posterior (parietal) branch curves backward and

roughly to the line of the underlying precentral gyrus of the

rior angle of the parietal bone, and its course corresponds

(frontal) branch deeply grooves or tunnels the anteroinfe

middle cranial fossa is described on page 598. The anterior

Its further course in the

geal and endosteal layers of dura.

lie between the menin

through the foramen spinosum to

ral bone (Fig. 11.20). To enter the cranial cavity, it passes

on the upper surface of the squamous part of the tempo

the cranial cavity and runs forward and laterally in a groove

artery in the infratemporal fossa (see page 598). It enters

arises from the maxillary

middle meningeal artery

The

damaged in head injuries.

tant is the middle meningeal artery, which is commonly

tebral arteries. From a clinical standpoint, the most impor

carotid, maxillary, ascending pharyngeal, occipital, and ver

Numerous arteries supply the dura mater from the internal

Dural Arterial Supply

greater occipital nerve.

the neck and back of the scalp along the distribution of the

level of the tentorium produces referred pain to the back of

of the head. Stimulation of the dural endings below the

produces referred pain to an area of skin on the same side

trigeminal nerve above the level of the tentorium cerebelli

of headache. Stimulation of the sensory endings of the

is sensitive to stretching, which produces the sensation

Numerous sensory endings are in the dura. The dura

the dura.

nerves and branches from the sympathetic system pass to

Branches of the trigeminal, vagus, and first three cervical

pituitary gland (Fig. 11.12).

small opening in its center allows passage of the stalk of the

mater that forms the roof for the sella turcica (Fig. 11.6). A

is a small circular fold of dura

diaphragma sellae

The

Its posterior fixed margin contains the occipital sinus.

projects forward between the two cerebellar hemispheres.

mater that is attached to the internal occipital crest and

is a small, sickle-shaped fold of dura

falx cerebelli

The

to the occipital bone (Fig. 11.10).

petrous bone, and the transverse sinus along its attachment

ebri, the superior petrosal sinus along its attachment to the

The straight sinus runs along its attachment to the falx cer

upper and lower surfaces of the tentorium, respectively.

The falx cerebri and the falx cerebelli are attached to the

trigeminal nerve and the trigeminal ganglion (Fig. 11.11).

beneath the superior petrosal sinus to form a recess for the

bone, the lower layer of the tentorium is pouched forward

Close to the apex of the petrous part of the temporal

Dural Nerve Supply

-
-

542

CHAPTER 11

The Head and Neck

hypophysis cerebri

anterior clinoid process

diaphragma sellae

dorsum sellae

oculomotor nerve

tentorium cerebelli

trochlear nerve

tegmentum

tentorial notch

superior colliculus

cerebral aqueduct

substantia nigra

crus cerebri

posterior cerebral artery

superior cerebellar artery

posterior communicating artery

internal carotid artery

ophthalmic artery

optic nerve

olfactory tract

olfactory bulb

infundibulum

tuber cinereum

posterior

lobe

posterior

cerebral

artery

body of

sphenoid

basilar artery

sphenoidal sinus

anterior lobe

hypophysis cerebri

diaphragma sellae

cavernous
sinus

oculomotor
nerve

trochlear
nerve

ophthalmic
nerve

maxillary
nerve

abducent
nerve

cavity of nose

internal carotid artery

sphenoidal sinus

nerve of pterygoid canal

FIGURE 11.12

nial nerves.

through the body of the sphenoid showing the hypophysis cerebri and the cavernous sinuses. Note the position of the cra

Sagittal section through the sella turcica showing the hypophysis cerebri.

The forebrain has been removed, leaving the midbrain, the hypophysis cerebri, and the internal carotid and

basilar arteries in position. B.

C. Coronal section

Basic Anatomy

are widely separated to form the

the brain, and in certain situations the arachnoid and pia

The arachnoid bridges over the sulci on the surface of

cerebrospinal fluid.

is filled with

which

subarachnoid space,

and from the pia by the

space,

subdural

separated from the dura by a potential space, the

internally and the dura mater externally (Fig. 11.2). It is

brane covering the brain and lying between the pia mater

The arachnoid mater is a delicate, impermeable mem

Arachnoid Mater of the Brain

the arteries.

plexus or the sphenoparietal sinus. The veins lie lateral to

dle meningeal artery and drains into the pterygoid venous

middle meningeal vein follows the branches of the mid

lie in the endosteal layer of dura. The

meningeal veins

The

Dural Venous Drainage

543

subarachnoid cisternae.

ies and veins lie in the space, as do the cranial nerves

through the subarachnoid space. All the cerebral arter

and from the brain to the skull or its foramina must pass

It is important to remember that structures passing to

cerebrospinal fluid diffuses into the bloodstream.

(Fig. 11.2). Arachnoid villi serve as sites where the

lations

arachnoid granu

tions of arachnoid villi are referred to as

most numerous along the superior sagittal sinus. Aggrega

The arachnoid villi are

arachnoid villi.

sinuses to form

In certain areas, the arachnoid projects into the venous

(Fig. 11.2). The arachnoid fuses with the epineurium of the

the substance of the brain carry a sheath of pia with them.

fuses with their epineurium. The cerebral arteries entering

est sulci (Fig. 11.2). It extends over the cranial nerves and

the brain, covering the gyri and descending into the deep

The pia mater is a vascular membrane that closely invests

Pia Mater of the Brain

tively protects the brain from trauma.

medium in which the brain floats. This mechanism effec

neuronal activity, the cerebrospinal fluid provides a fluid

In addition to removing waste products associated with

fusing through their walls.

the bloodstream by passing into the arachnoid villi and dif

(see Fig. 12.7). Eventually, the fluid enters

sacral vertebra

second

subarachnoid space extends down as far as the

spheres and downward around the spinal cord. The spinal

culates both upward over the surfaces of the cerebral hemi

ventricle and so enters the subarachnoid space. It now cir

brain through the three foramina in the roof of the fourth

of the brain. It escapes from the ventricular system of the

within the lateral, third, and fourth ventricles

choroid

is produced by the

cerebrospinal fluid

The

as the eyeball (see page 554).

subarachnoid space extends around the optic nerve as far

fuses with the sclera of the eyeball (Fig. 11.25). Thus, the

extends into the orbital cavity through the optic canal and

optic nerve, the arachnoid forms a sheath for the nerve that

nerves at their point of exit from the skull. In the case of the

plexuses

-
-

Intracranial Hemorrhage

ily blood-stained cerebrospinal fluid through a lumbar puncture

from an angioma. The symptoms, which are sudden in onset,

toms. In both forms, the blood clot must be removed through burr

depending on the speed of accumulation of fluid in the subdu

Acute and chronic forms of the clinical condition occur,

to accumulate in the potential space between the dura and the

tal sinus. The cause is usually a blow on the front or the back of

To stop the hemorrhage, the torn artery or vein must be

vascular lesions. Four varieties are considered here: extradural,

Intracranial hemorrhage may result from trauma or cerebral

subdural, subarachnoid, and cerebral.

Extradural hemorrhage results from injuries to the meningeal

arteries or veins. The most common artery to be damaged is the

anterior division of the middle meningeal artery. A comparatively

minor blow to the side of the head, resulting in fracture of the

skull in the region of the anteroinferior portion of the parietal

bone, may sever the artery. The arterial or venous injury is espe-

cially liable to occur if the artery and vein enter a bony canal in

this region. Bleeding occurs and strips up the meningeal layer of

dura from the internal surface of the skull. The intracranial pres-

sure rises, and the enlarging blood clot exerts local pressure on

the underlying motor area in the precentral gyrus. Blood may

also pass outward through the fracture line to form a soft swell-

ing under the temporalis muscle.

ligated or plugged. The burr hole through the skull wall should

be placed about 1 to 1.5 in. (2.5 to 4 cm) above the midpoint of the

zygomatic arch.

Subdural hemorrhage results from tearing of the superior

cerebral veins at their point of entrance into the superior sagit-

the head, causing excessive anteroposterior displacement of the

brain within the skull.

This condition, which is much more common than middle

meningeal hemorrhage, can be produced by a sudden minor

blow. Once the vein is torn, blood under low pressure begins

arachnoid. In about half the cases, the condition is bilateral.

ral space. For example, if the patient starts to vomit, the venous

pressure will rise as a result of a rise in the intrathoracic pres-

sure. Under these circumstances, the subdural blood clot will

increase rapidly in size and produce acute symptoms. In the

chronic form, over a course of several months, the small blood

clot will attract fluid by osmosis so that a hemorrhagic cyst is

formed, which gradually expands and produces pressure symp-

holes in the skull.

Subarachnoid hemorrhage results from leakage or rupture of

a congenital aneurysm on the circle of Willis or, less commonly,

include severe headache, stiffness of the neck, and loss of con-

sciousness. The diagnosis is established by withdrawing heav-

(spinal tap).

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

(continued)

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