HEAD AND NECK 23.pdf

❖ BONES OF THE HEAD AND NECK
❖ TRIANGLES OF THE NECK
❖ CERVICAL FASCIAE
❖ SCALP
❖ CERVICAL PLEXUS
❖ EXTERNAL CAROTID ARTERY
❖ THYROID AND PARATHYROID GLANDS
❖ INFRAHYOID MUSCLES
❖ SUPRAHYOID MUSCLES
❖ LARYNX
❖ PHARYNX

In the midline, from above down, can be felt
1◊◊the hyoid bone—at the level of C3;
2◊◊the notch of the thyroid cartilage—at the level of
C4;
3◊◊the cricothyroid ligament—important in
cricothyroid puncture;
4◊◊the cricoid cartilage—terminating in the trachea
at C6;
5◊◊the rings of the trachea, over the second and
third of which can be rolled the isthmus of the
thyroid gland;
6◊◊the suprasternal notch.

Note that the lower border of the cricoid is an important level in
the neck; it corresponds not only to the level of the 6th cervical
vertebra but also to:
1◊◊the junction of the larynx with the trachea;
2◊◊the junction of the pharynx with the oesophagus;
3◊◊the level at which the inferior thyroid artery and the middle
thyroid vein enter the thyroid gland;
4◊◊the level at which the vertebral artery enters the transverse
foramen in the 6th cervical vertebra;
5◊◊the level at which the superior belly of the omohyoid crosses
the carotid sheath;
6◊◊the level of the middle cervical sympathetic ganglion;
7◊◊the site at which the carotid artery can be compressed
against the transverse process of C6 (the carotid tubercle).

Triangles of the Anterior Neck are formed by the
sternocleidomastoid muscle as it passes diagonally across the
quadrilateral area formed between the anterior border of the
trapezius muscle and the anterior midline of the neck, and
between the inferior border of the mandible, superiorly, and
the superior surface of the middle third of the clavicle,
inferiorly. This divides the neck into two principal triangles, the
anterior and posterior cervical triangles. Each of these
triangles is further subdivided by muscles and bones; thus,
each major triangle is made up of several subtriangles. Each
triangle possesses its own anatomical component parts,
including muscles, veins, nerves, etc. All of the cervical
triangles are bilateral (right and left sides) with the exception
of the submental triangle, which spans across the midline.
CERVICAL TRIANGLES CONT.

The scalp is the part of the head that extends from
the superciliary arches anteriorly to the external
occipital protuberance and superior nuchal lines
posteriorly. Laterally it continues inferiorly to the
zygomatic arch.
❖ The scalp is a multilayered structure with layers
that can be defined by the word itself: S-skin;
❖ C-connective tissue (dense);
❖ A-aponeurotic layer;
❖ L-loose connective tissue;
❖ P-pericranium
SCALP CONT.

Layers
Examining the layers of the
scalp reveals that the first
three layers are tightly held
together, forming a single unit.
This unit is sometimes referred
to as the scalp proper and is
the tissue torn away during
serious 'scalping' injuries.
SCALP CONT.

Skin
The skin is the outer layer
of the scalp. It is similar
structurally to skin
throughout the body with
the exception that hair is
present on a large amount
of it.
SCALP CONT.

Connective tissue (dense)
Deep to the skin is dense
connective tissue. This layer
anchors the skin to the third
layer and contains the
arteries, veins, and nerves
supplying the scalp. When the
scalp is cut, the dense
connective tissue surrounding
the vessels tends to hold cut
vessels open. This results in
profuse bleeding
SCALP CONT.

Aponeurotic layer
The deepest layer of the first 3
layers is the aponeurotic layer.
Firmly attached to the skin by the
dense connective tissue of the
second layer, this layer consists of
the occipitofrontalis muscle, and
has a frontal belly anteriorly, an
occipital belly posteriorly, and an
aponeurotic tendon-the
epicranial aponeurosis (galea
aponeurotica)-connecting the
two
SCALP CONT.

Loose connective tissue
A layer of loose connective
tissue separates the
aponeurotic layer from the
pericranium and facilitates
movement of the scalp proper
over the calvaria. Because of its
consistency, infections tend to
localize and spread through the
loose connective tissue.
SCALP CONT.

Pericranium
The pericranium is the
deepest layer of the scalp and
is the periosteum on the outer
surface of the calvaria. It is
attached to the bones of the
calvaria, but is removable,
except in the area of the
sutures.
SCALP CONT.

CERVICAL FASCIAE
The fascial compartments of
the neck. The fascial planes of
the neck are of considerable
importance to the surgeon;
they form convenient lines of
cleavage through which he may
separate the tissues in
operative dissections and they
delimit the spread of
pus in neck infections.
The superficial fascia is a thin
fatty membrane enclosing the
platysma.

The deep fascia can be divided
into three layers.
1. The enveloping fascia
invests the muscles of the
neck. It is attached to all the
bony landmarks at the upper
and lower margin of the neck:
above, to the mandible,
zygomatic arch, mastoid
process and superior nuchal
line; below, to the manubrium,
clavicle, acromion and
scapular spine. Posteriorly, the
ligamentum nuchae provides a
longitudinal line of attachment
CERVICAL FASCIAE CONT.

This enveloping fascia splits to
enclose the trapezius, the
sternocleidomastoid, the strap
muscles and the parotid and
submandibular glands. The
external jugular vein pierces
the deep fascia above the
clavicle. If the vein is divided
here, it is held open by the
deep fascia which is attached
to its margins, air is sucked
into the vein lumen during
inspiration and a fatal air
embolism may ensue.

2◊◊The prevertebral fascia passes
across the vertebrae and preverte-
bral muscles behind the oesopha-
gus, the pharynx and the great
vessels. Above it is attached to
the base of the skull. Laterally, the
fascia covers the scalene muscles
together with the phrenic nerve,
as this lies on scalenus anterior,
and the emerging brachial plexus
and subclavian artery. These
structures carry with them a
sheath formed from the preverte-
bral fascia, which becomes the
axillary sheath.

Inferiorly, the fascia blends with
the anterior longitudinal ligament
of the upper thoracic vertebrae in
the posterior mediastinum. Pus
from a tuberculous cervical
vertebra bulges behind this
dense fascial layer and may form
a midline swelling in the
posterior wall of the pharynx. The
abscess may then track laterally,
deep to the prevertebral fascia, to
a point behind the
sternocleidomastoid. Rarely, pus
has tracked down along the
axillary sheath into the arm.

3◊◊The pretracheal fascia
encloses the ‘visceral compart-
ment of the neck’. Extending
from the hyoid above to the
fibrous pericardium below, it
encloses larynx and trachea,
pharynx and oesophagus and
the thyroid gland. A separate
tube of fascia forms the carotid
sheath, containing carotid,
internal jugular and vagus
nerve and bearing the cervical
sympathetic chain in its
posterior wall.

MANDIBLE
Mandible. Lateral
aspect (top view).
Superior aspect
(middle view).
Medial aspect
(bottom view). (A)
Coronoid process.
(B) Mandibular
condyle. (C)
Mandibular notch.
(D) Body of
mandible. (E) Ramus
of mandible. (F)
Submandibular
fossa. (G)
Sublingual fossa.

The neurocranium encloses the
brain, labyrinth, and middle
ear. The outer and inner tables
of the skull are connected by
cancellous bone and marrow
spaces (diploë). The bones of
the roof of the cranium
(calvaria) of adolescents and
adults are rigidly connected by
sutures and cartilage
(synchondroses).

The coronal suture extends across
the frontal third of the cranial roof.
The sagittal suture lies in the
midline, extending backward from
the coronal suture and bifurcating
over the occiput to form the
lambdoid suture. The area of
junction of the frontal, parietal,
temporal, and sphenoid bones is
called the pterion; below the pterion
lies the bifurcation of the middle
meningeal artery.

NEUROCRANIUM
FORAMEN CAECUM
CRISTA GALLI
CRIBRIFORM PLATE
OPTIC FORAMEN
FORAMEN ROTUNDUM
FORAMEN OVALE
FORAMEN SPINOSUM
TEMPORAL BONE
INTERNAL ACUOSTIC M
FORAMEN MAGNUM
PARIETAL BONE
INTERNAL OCCIPITAL
CREST
ANTERIOR CRANIAL FOSSA
FRONTAL BONE
SPHENOID BONE
SPHENOID BONE < WING
SPHENOID BONE > WING
SELLA TURCICA
DORSUM SELLAE
FORAMEN LACERUM
PETROUS PART OF
TEMPORAL BONE
JUGULA FORAMEN
POSTERIOR CRANIAL FOSSA
MASTOID FORAMEN
OCCIPITAL BONE

The inner skull base forms the
floor of the cranial cavity, which is
divided into anterior, middle, and
posterior cranial fossae. The
anterior fossa lodges the olfactory
tracts and the basal surface of the
frontal lobes; the middle fossa, the
basal surface of the temporal
lobes, hypothalamus, and pituitary
gland; the posterior fossa, the
cerebellum, pons, and medulla.
NEUROCRANIUM

NEUROCRANIUM
The anterior and middle fossae
are demarcated from each other
laterally by the posterior edge of
the (lesser) wing of the sphenoid
bone, and medially by the jugum
sphenoidale. The middle and
posterior fossae are demarcated
from each other laterally by the
upper rim of the petrous pyramid,
and medially by the dorsum
sellae.

CERVICAL VERTEBRAE
There are seven cervical vertebrae,
and they constitute the most superior
extension of the vertebral column.
The superior two, the atlas and axis,
are greatly modified to support the
head and permit its rotation at the
atlantoaxial joint. The seventh
cervical vertebra (C7) is also modified
but will not be treated separately
here.
Interposed between any two
vertebrae is an intervertebral disc, as
well as other cartilaginous structures
P.81
involved in regions of facets to
facilitate smooth, frictionless
movement and provide cushioning
and support for the whole vertebral
column.

CERVICAL VERTEBRAE CONT.
The typical cervical vertebra, as any other typical
vertebra, has a large, anteriorly directed body from which
the posterior vertebral arch is directed dorsally. This arch
encloses the vertebral foramen. All the vertebral foramina
together constitute the vertebral canal, which houses the
spinal cord, meninges, and associated vessels. The
posterior vertebral arch consists of two short, anterior
pedicles and two broader, posterior laminae. Jutting out
from the two laminae are two superior articular
processes, two inferior articular processes, two transverse
processes, and a single posteriorly and inferiorly directed
spinous process.

The superior and inferior aspects of the pedicles bear
vertebral notches known as the superior and inferior
vertebral notches. As two vertebrae articulate with
each other, the superior notch of the lower vertebra
and the inferior notch of the upper vertebra form the
invertebral foramen, through which the spinal nerves
leave the vertebral canal.
The transverse processes of all cervical vertebrae
(except the seventh) are pierced by the large foramen
transversarium, housing the vertebral vessels and
associated sympathetic plexus.

The seventh cervical vertebra has a small or doubled
foramen transversarium. The superior articular
processes project cranially, bearing the posteriorly
directed articular facets. The inferior articular
processes project caudally, with their articular facets
directed anteriorly.
The superior surface of the body is somewhat concave
and presents an upward-curving lip on either side. The
inferior surface of the body is slightly concave in an
anteroposterior direction, while being convex in the
transverse plane. The bifid spinous process (longest in
C7) projects posteriorly and inferiorly.

CERVICAL PLEXUS
Levator scapulae Upper
Levator scapulae Lower
Superior root
Inferior root

❖This plexus is formed by communications between the ventral rami of
the upper four cervcal nerves which emerge superior to the
corresponding vertebrae.
❖ The plexus lies posterior to the internal jugular vein and the
prevertebral fascia, between the level of the root of the auricle and the
superior border of the thyroid cartilage.
❖The ventra rami of the cervical nerve emerge between the
corresponding transverse muscles (rectus capitis anterior and lateralis
in the ase f the first cervical and anterior to scaneus medius (except the
first cervical) they communicate serially with each other, that between
the fourth and fifth uniting the cervical and brachial plexuses, and been
enlarged when the brachial plexus is prefixed i.e when the plexus has a
higher than usual level of origin.
CERVICAL PLEXUS CONT.

1. Communicating: (a) gray ramus communications to each of
the first four cervical ventral rami from the superior cervical
ganglion. (b) a branch of the first cervical ventral ramus which
depends to join or communicate with the hypoglossal nerve.
This branch usually supplies geniohyoid and thyrohyoid and
forms the superior root of the ansa cervicalis (c) sensory
branch from the second, third and fourth to the accessory
nerve for sternocleidomastoid and trapezius .
2. Cuteneous branches : (lesser occipital nerves and great
auricular nerve)
3. Muscular branches: pass to the diaphragm and infrahyoid,
prevertebral, scalene, intraverse and levator scapulae
muscles.
Branches of cervical plexus

This joint lies between the condyloid process of the
mandible and the articular fossa and articular eminence
of the temporal bone. The articular surfaces are covered
with fibrous (not hyaline) cartilage and there is also a
fibrocartilaginous articular disc dividing the joint cavity
into an upper and lower compartment. The capsular
ligament surrounding the joint is reinforced by a lateral
temporomandibular ligament and by the spheno-
mandibular ligament which passes from the spine of the
sphenoid to the lingular process immediately in front of
the mandibular foramen; this ligament represents part
of the primitive 1st arch, or Meckel’s cartilage.
THE TEMPOROMANDIBULAR JOINT

The lower jaw can be depressed, elevated, protruded,
retracted and moved from side to side.
The muscles effecting these movements are:
•◊◊elevation—temporalis, masseter, medial pterygoid;
•◊◊depression — lateral pterygoid, together with
digastric, mylohyoid and geniohyoid (assisted by
gravity—your jaw drops open when you fall asleep in a
lecture);
•◊◊retraction—posterior fibres of temporalis;
•◊◊protraction—lateral and medial pterygoids together;
•◊◊side to side—lateral and medial pterygoids together,
acting alternately on each side.

It has lateral and medial relations. Note them
Nerve supply from two sources: Auriculotemporal
and Masseteric nerves. Note their origins.
The blood supply are from Superficial temporal,
maxillary, auriculotemporal and masseteric arteries
APPLIED ANATOMY INCLUDE:
1. Forward dislocation
2. Anterior dislocation
3. Reduction of the TMJ
4. Etc.

TONGUE
The tongue is a muscular organ which has a free,
mobile, anterior part, horizontal at rest, and a more
fixed, posterior, vertical part (the roof). The anterior
part is in the mouth and the posterior part is in th
pharynx.

TONGUE
The tongue consists of a
buccal and a pharyngeal
portion separated by a V-
shaped groove on its
dorsal surface, the
sulcus terminalis. At the
apex of this groove is a
shallow depression, the
foramen caecum,
marking the
embryological origin of
the thyroid gland.

TONGUE
Immediately anterior to
the sulcus lie a row of
large vallate papilliae. The
under aspect of the
tongue bears the median
frenulum linguae; the
mucosa is thin on this
surface and the lingual
veins can thus be seen on
either side of the
frenulum.

The lingual nerve and the lingual artery are medial
to the vein but not visible. More laterally can be
seen a fringed fold of mucous membrane termed
the plica fimbriata. On either side of the base of
the frenulum can be seen the orifice of the
submandibular duct on its papilla. Inspect this in a
mirror and note the discharge of saliva when you
press on your sub-mandibular gland just below the
angle of the jaw.
TONGUE

The thick stratified squamous mucosa of the
dorsum of the tongue bears papillae over the
anterior two-thirds back as far as the sulcus
terminalis. These papillae (particularly the vallate)
bear the taste buds. The posterior one-third has no
papillae but carries numerous lymphoid nodules
which, with the palatine tonsils and adenoids,
make up the lymphoid ring of Waldeyer. Small
glands are scattered throughout the submucosa of
the dorsum; these are predominantly serous
anteriorly and mucous posteriorly.
TONGUE

The tongue is divided by a median vertical fibrous
septum, as indicated on the dorsum by a shallow
groove. On each side of this septum are the
intrinsic and extrinsic muscles of the tongue. The
intrinsic muscles are disposed in vertical,
longitudinal and transverse bundles; they alter the
shape of the tongue. The extrinsic muscles move
the tongue as a whole. They pass to the tongue
from the symphysis of the mandible, the hyoid,
styloid process and the soft palate, respectively
the genioglossus, hyoglossus, styloglossus and
palatoglossus.
TONGUE

TONGUE
Blood supply is from the lingual branch of the
external carotid artery.
Lymph drainage of the mucosa of the tongue can
be grouped into three:
1◊the tip drains to the submental nodes;
2◊the anterior two-thirds drains to the
submental and submandibular nodes and
thence to the lower nodes of the deep cervical
chain along the carotid sheath;
3◊the posterior one-third drains to the upper
nodes of the deep cervical chain.

TONGUE
Nerve supply
The anterior two-thirds of the tongue receives its
sensory supply from the lingual branch of V which
also transmits the gustatory fibres of the chorda
tympani (VII). Common sensation and taste to the
posterior one-third, including the vallate papillae, are
derived from IX. A few fibres of the superior laryngeal
nerve (X) carry sensory fibres from the posterior part
of the tongue. All the muscles of the tongue except
palatoglossus are supplied by XII; palatoglossus, a
muscle of the soft palate, is innervated by the
pharyngeal branch of X.

TONGUE
DEVELOPMENT
Asmall nodule, the tuberculum
impar, is the first evidence of the
developing tongue in the floor of
the pharynx. This is soon covered
over by the lingual swellings, one
on each side, derived from the
first branchial arch. These fuse in
the midline to form the definitive
anterior two-thirds of the tongue
supplied by V and reinforced by
chorda tympani.

DEVELOPMENT
Posteriorly, this mass meets the
copula (or hypobranchial eminence),
a central swelling in the pharyngeal
floor which represents the 2nd, 3rd
and 4th arches and which forms the
posterior one-third of the tongue
(nerve supply IX and X). The tongue
muscles derive from the occipital
myotomes which migrate forward
dragging with them their nerve
supply (XII, the hypoglossal nerve).
TONGUE

The nasal cavity is divided into right and left halves by a
median nasal septum formed by the perpendicular plate of
the ethmoid bone, the septal cartilage and the vomer. Each
cavity extends from the nostril (or anterior nares) in front to
the posterior nasal aperture behind, communicating
through the latter with the nasopharynx.

The lateral wall is very irregular, due to the projection of the
three conchae (superior, middle and inferior) and the underly-
ing meatuses. The superior meatus receives the opening of the
posterior ethmoidal air cells. Opening into the middle meatus
are (antero-posteriorly) the frontal and maxillary sinuses and
the anterior and middle ethmoidal air cells. Only the nasolacri-
mal duct opens, in solitary splendour, into the inferior meatus.

The roof of the cavity is horizontal in its central portion,
where it is formed by the cribriform plate of the ethmoid,
but slopes downwards both anteriorly (the frontal and
nasal bones) and posteriorly (the sphenoid). The floor
corresponds to the roof of the mouth; it comprises the
palatine process of the maxilla, the horizontal process
of the palatine bone and the soft palate.

There are four paranasal air sinuses - the ethmoidal cells, and
the sphenoidal, maxillary, and frontal sinuses . Each is named
according to the bone in which it is found. The paranasal
sinuses develop as outgrowths from the nasal cavities and
erode into the surrounding bones. All are: lined by respiratory
mucosa, which is ciliated and mucus secreting; open into the
nasal cavities; innervated by branches of the trigeminal nerve
[V].

The frontal sinuses, one on each side, are variable in size and are
the most superior of the sinuses. Each is triangular in shape and is in
the part of the frontal bone under the forehead. The base of each
triangular sinus is oriented vertically in the bone at the midline above
the bridge of the nose and the apex is laterally approximately one-
third of the way along the upper margin of the orbit. Each frontal
sinus drains onto the lateral wall of the middle meatus via the
frontonasal duct, which penetrates the ethmoidal labyrinth and
continues as the ethmoidal infundibulum at the front end of the
hiatus semilunaris . The frontal sinuses are innervated by branches
of the supra-orbital nerve from the ophthalmic nerve [V1]. Their blood
supply is from branches of the anterior ethmoidal arteries.

The ethmoidal cells on each side fill the ethmoidal
labyrinth. Each cluster of cells is separated from the orbit
by the thin orbital plate of the ethmoidal labyrinth, and from
the nasal cavity by the medial wall of the ethmoidal
labyrinth.The ethmoidal cells are formed by a variable
number of individual air chambers, which are divided into
anterior, middle, and posterior ethmoidal cells based on the
location of their apertures on the lateral wall of the nasal
cavity: the anterior ethmoidal cells open into the
ethmoidal infundibulum or the frontonasal duct; the middle
ethmoidal cells open onto the ethmoidal bulla, or onto the
lateral wall just above this structure;

the posterior ethmoidal cells open onto the lateral wall of
the superior nasal meatus. Because the ethmoidal cells
often erode into bones beyond the boundaries of the
ethmoidal labyrinth, their walls may be completed by the
frontal, maxillary, lacrimal, sphenoid, and palatine bones.
The ethmoidal cells are innervated by: the anterior and
posterior ethmoidal branches of the nasociliary nerve
from the ophthalmic nerve [V1]; the maxillary nerve [V2] via
orbital branches from the pterygopalatine ganglion. The
ethmoidal cells receive their blood supply through
branches of the anterior and posterior ethmoidal arteries.

Maxillary sinuses .The maxillary sinuses, one on each
side, are the largest of the paranasal sinuses and
completely fill the bodies of the maxillae. Each is pyramidal
in shape with the apex directed laterally and the base deep
to the lateral wall of the adjacent nasal cavity. The medial
wall or base of the maxillary sinus is formed by the maxilla,
and by parts of the inferior concha and palatine bone that
overlie the maxillary hiatus. The opening of the maxillary
sinus is near the top of the base, in the center of the hiatus
semilunaris, which grooves the lateral wall of the middle
nasal meatus.

Relationships of the maxillary sinus are as
follows: the superolateral surface (roof) is
related above to the orbit; the anterolateral
surface is related below to the roots of the
upper molar and premolar teeth and in front to
the face; the posterior wall is related behind to
the infratemporal fossa. The maxillary sinuses
are innervated by infra-orbital and alveolar
branches of the maxillary nerve [V2], and
receive their blood through branches from the
infra-orbital and superior alveolar branches of
the maxillary arteries.

The sphenoidal sinuses, one on either side within the
body of the sphenoid, open into the roof of the nasal
cavity via apertures on the posterior wall of the spheno-
ethmoidal recess. The apertures are high on the anterior
walls of the sphenoid sinuses. The sphenoidal sinuses
are related: superiorly to the cranial cavity, particularly to
the pituitary gland and to the optic chiasm; laterally, to
the cranial cavity, particularly to the cavernous sinuses;
anteroinferiorly, to the nasal cavities. Because only thin
shelves of bone separate the sphenoidal sinuses from
the nasal cavities below and hypophyseal fossa
superiorly,

the pituitary gland can be surgically approached
through the roof of the nasal cavities by passing first
through the anteroinferior aspect of the sphenoid
bone and into the sphenoidal sinuses and then
through the top of the sphenoid bone into the
hypophyseal fossa. Innervation of the sphenoidal
sinuses is provided by: the posterior ethmoidal
branch of the ophthalmic nerve [V1]; the maxillary
nerve [V2] via orbital branches from the
pterygopalatine ganglion. The sphenoidal sinuses are
supplied by branches of the pharyngeal arteries
from the maxillary arteries.

The pterygopalatine fossa is an inverted 'tear-drop' shaped
space between bones on the lateral side of the skull
immediately posterior to the maxilla. Although small in size,
the pterygopalatine fossa communicates via fissures and
foramina in its walls with: the middle cranial fossa;
infratemporal fossa; floor of the orbit; lateral wall of the
nasal cavity; oropharynx; roof of the oral cavity.
Because of its strategic location, the pterygopalatine fossa is
a major site of distribution for the maxillary nerve [V2] and for
the terminal part of the maxillary artery. In addition,
parasympathetic fibers from the facial nerve [VII] and
sympathetic fibers originating from the T1 spinal cord level
join branches of the maxillary nerve [V2] in the
pterygopalatine fossa.

The pterygopalatine ganglion, which contains cell
bodies for the postganglionic parasympathetic fibers
in the greater petrosal branch of the facial nerve
[VII] that will synapse with the preganglionic
parasympathetic fibers, is formed in association with
branches of the maxillary nerve [V2] in the
pterygopalatine fossa. All the upper teeth receive
their innervation and blood supply from the
maxillary nerve [V2] and the terminal part of the
maxillary artery, respectively, that pass through the
pterygopalatine fossa.

Infratemporal fossa .The wedge-shaped infratemporal fossa
is inferior to the temporal fossa and between the ramus of
the mandible laterally and the wall of the pharynx medially. It
has a roof, a lateral wall, and a medial wall, and is open to
the neck posteroinferiorly; the roof is formed by the inferior
surfaces of the greater wing of the sphenoid and the
temporal bone, contains the foramen spinosum, foramen
ovale, and the petrotympanic fissure, and lateral to the
infratemporal crest of the greater wing of the sphenoid, is
open superiorly to the temporal fossa; the lateral wall is the
medial surface of the ramus of the mandible, which contains
the opening to the mandibular canal;

the medial wall is formed anteriorly by the lateral plate of the pterygoid
process and more posteriorly by the pharynx and by two muscles of the soft
palate (tensor and levator veli palatini muscles), and contains the pterygo-
maxillary fissure anteriorly, which allows structures to pass between the
infratemporal and pterygopalatine fossae; the anterior wall is formed by part
of the posterior surface of the maxilla, contains the alveolar foramen, and the
upper part opens as the infra-orbital fissure into the orbit. Major contents of
the infratemporal fossa include the sphenomandibular ligament, medial and
lateral pterygoid muscles, the maxillary artery, the mandibular nerve, branches
of the facial nerve, and the glossopharyngeal nerve, and the pterygoid plexus of
veins. Sphenomandibular ligament . The sphenomandibular ligament is an
extracapsular ligament of the temporomandibular joint. It is attached
superiorly to the spine of the sphenoid bone and expands inferiorly to attach to
the lingula of the mandible and the posterior margin of the mandibular foramen

The medial pterygoid muscle is quadrangular in shape
and has deep and superficial heads. the deep head is
attached above to the medial surface of the lateral plate of
the pterygoid process and the associated surface of the
pyramidal process of the palatine bone, and descends
obliquely downwards, medial to the sphenomandibular
ligament, to attach to the roughened medial surface of the
ramus of mandible near the angle of mandible; the
superficial head originates from the tuberosity of the
maxilla and adjacent pyramidal process of the palatine
bone and joins with the deep head to insert on the
mandible.

The medial pterygoid mainly elevates the mandible.
Because it passes obliquely backwards to insert into the
mandible, it also assists the lateral pterygoid muscle in
protruding the lower jaw. The medial pterygoid is
innervated by the nerve to medial pterygoid from the
mandibular nerve [V3]. Lateral pterygoid The lateral
pterygoid is a thick triangular muscle and like the medial
pterygoid muscle has two heads: the upper head
originates from the roof of the infratemporal fossa (inferior
surface of the greater wing of the sphenoid and the
infratemporal crest) lateral to the foramen ovale and
foramen spinosum;

the lower head is larger than the upper head and
originates from the lateral surface of the lateral plate of the
pterygoid process, and the inferior part insinuates itself
between the cranial attachments of the two heads of the
medial pterygoid. The fibers from both heads of the lateral
pterygoid muscle converge to insert into the pterygoid
fovea of the neck of mandible and into the capsule of the
temporomandibular joint in the region where the capsule is
attached internally to the articular disc. Unlike the medial
pterygoid muscle whose fibers tend to be oriented
vertically, those of the lateral pterygoid are oriented almost
horizontally.

As a result, when lateral pterygoid contracts it pulls
the articular disc and head of the mandible forward
onto the articular tubercle and is therefore the
major protruder of the lower jaw. The lateral
pterygoid is innervated by the nerve to lateral
pterygoid from the mandibular nerve [V3]. When
lateral and medial pterygoids contract on only one
side, the 'chin' moves to the opposite side. When
opposite movements at the two
temporomandibular joints are coordinated, a
'chewing' movement results.

The pharynx is a musculofascial half-cylinder
that links the oral and nasal cavities in the head
to the larynx and esophagus in the neck. The
pharyngeal cavity is a common pathway for air
and 'food'. The pharynx is attached above to
the base of the skull and is continuous below,
approximately at the level of vertebra C6, with
the top of the esophagus. It is a passageway
for air and food. 14−16 cm long, it extends from
the fornix to the beginning of the esophagus.

The walls of the pharynx are
attached anteriorly to the margins of
the nasal cavities, oral cavity, and
larynx. Based on these anterior
relationships the pharynx is
subdivided into three regions, the
nasopharynx, oropharynx, and
laryngopharynx: the posterior
apertures (choanae) of the nasal
cavities open into the nasopharynx; the posterior opening of the
oral cavity (oropharyngeal isthmus) opens into the oropharynx;
the superior aperture of the larynx (laryngeal inlet) opens into
the laryngopharynx

In addition to these openings,
the pharyngeal cavity is related
anteriorly to the posterior one-
third of the tongue and to the
posterior aspect of the larynx.
The pharyngotympanic tubes
open into the lateral walls of the
nasopharynx. Lingual, pharyn-
geal, and palatine tonsils
are on the deep surface of the pharyngeal walls. The pharynx
is separated from the vertebral column behind by a thin
retropharyngeal space containing loose connective tissue

Although the soft palate is generally considered as
part of the roof of the oral cavity, it is also related
to the pharynx. The soft palate is attached to the
posterior margin of the hard palate and is a type
of 'flutter-valve' that can:
•swing up (elevate) to close the pharyngeal
isthmus, and seal off the nasopharynx from the
oropharynx;
•swing down (depress) to close the oropharyngeal
isthmus and seal off the oral cavity from the
oropharynx.

The ear is the organ of hearing and balance. It has three
parts:
1. the external ear consisting of the part attached to the
lateral aspect of the head and the canal leading inward;
2.the middle ear-a cavity in the petrous part of the
temporal bone bounded laterally, and separated from the
external canal, by a membrane and connected internally
to the pharynx by a narrow tube;
3. the internal ear consisting of a series of cavities
within the petrous part of the temporal bone between the
middle ear laterally and the internal acoustic meatus
medially.

The internal ear
converts the
mechanical
signals received
from the middle
ear, which start
as sound
captured by the
external ear,
into electrical signals to transfer information to the brain. The
internal ear also contains receptors that detect motion and
position.

1. EXTERNAL EAR. Auris externa. The part of the ear consisting of
the auricle (pinna) and external acoustic meatus.
2 External acoustic (auditory) meatus (canal). Meatus acusticus
externus. Flat, partly cartilaginous, partly bony, S-shaped canal
about 2.4 cm long with a diameter of about 6 mm.
3 External opening of acoustic canal. Porus acusticus extrnus.
Tympanic notch. Icisura tympanica. Defect between the greater
and lesser tympanic spines. In the newborn, it is the superior
gap between the still free ends of the tympanic ring.
4 Cartilaginous part of external acoustic meatus. Meatus
acusticus externus cartilagineus. Lateral, cartilaginous third of
the external acoustic meatus.

5. Cartilage of external acoustic meatus. Cartilago
meatus acustici. Together with the cartilage of the
pinna, it forms a groove that opens superiorly and
posteriorly.
6. Incisurae cartilaginis meatus acustici. Two fissures
in the cartilage of the external acoustic meatus. They
are bridged by connective tissue and are usually
directed anteriorly.
7. Lamina tragi. Lateral part of the meatal cartilage.
It lies in front of the external opening of the acoustic
meatus.

The pinna (auricle) is an ovoid-shaped structure with an
uneven surface filled with grooves and depressions.
Humans have one pinna on each side of the head.
The average length of the pinna is approximately
65mm (2.6 in) and the average width is approximately
35mm (1.4 in).In most adults the width of the pinna is
approximately 55% of its length.
Auricle (pinna) Expanded portion of the ear projecting
from the side of the head. It funnels sound waves into
the external acoustic canal. Helix Outer rim of the
auricle. It gives form and shape to the auricle. Earlobe
Fleshy inferior portion of the auricle.

129
PARTS OF THE PINNA
Fig.2: Diagram showing parts of the pinna
(Standring, 2005).
1.Helix
2Crus of helix
3.Auricular tubercle
4.Antihelix
5.Crura of helix
6.Triangular fossa
7.Scaphoid fossa
8.Concha of auricle
9.External acoustic meatus
10.Tragus
11.Antitragus
12.Intertragic notch
13.Lobule of auricle.

Tragus Small projection of the auricle, just
anterior to the external acoustic canal.
Antitragus Small, cartilaginous anterior
projection opposite the tragus. Antihelix
Semicircular ridge anterior to the greater
portion of the helix. Concha Depressed hollow
of the auricle. It funnels sound waves.
External acoustic canal Slightly S-shaped
tube extending inward to the tympanic
membrane. It contains glands that secrete
earwax for protection. Triangular fossa
Triangular depression in the superior part of
the antihelix

The internal ear consists essentially of a
complicated bony labyrinth made up of a
central vestibule, which communicates
posteriorly with three semicircular ducts
and anteriorly with the spiral cochlea. This
cavity contains a fluid known as perilymph
and encloses the membranous labyrinth,
comprising the utricle and saccule, which
communicate respectively with the
semicircular canals and the cochlear canal.
The duct system is filled with endolymph.

In each component of the membranous labyrinth
there are specialized sensory receptor areas known
as the maculae of the utricle and saccule, the
ampullary crests of the semicircular canals and the
spiral organ of Corti in the cochlea.
The disposition of the semicircular canals in three
planes at right angles to each other renders this
part of the labyrinth particularly well suited to
signal changes in position of the head. The organ of
Corti is adapted to record the sound vibrations
transmitted by the stapes at the oval window.

Salivary glands are glands that
open or secrete into the oral
cavity. Most are small glands in
the submucosa or mucosa of the
oral epithelium lining the tongue,
palate, cheeks, and lips, and
open into the oral cavity directly
or via small ducts. In addition to
these small glands are much
larger glands, which include the
paired parotid, submandibular,
and sublingual glands.

The parotid gland on each side is
entirely outside the boundaries
of the oral cavity in a shallow
triangular-shaped trench formed
by: the SCM muscle behind; the
ramus of mandible in front;
superiorly, the base of the
trench is formed by the external
acoustic meatus and the
posterior aspect of the
zygomatic arch.

The parotid duct passes anteriorly
across the external surface of the
masseter muscle and then turns
medially to penetrate the buccina-
tor muscle of the cheek and open
into the oral cavity adjacent to the
crown of the second upper molar
tooth. The parotid gland encloses
the external carotid artery, the
retromandibular vein, and the
origin of the extracranial part of
the facial nerve.

Submandibular glands The elongate submandibular glands are
smaller than the parotid glands, but larger than the sublingual
glands. Each is hook shaped: the larger arm of the hook is
directed forward in the horizontal plane below the mylohyoid
muscle and is therefore outside the boundaries of the oral
cavity-this larger superficial part of the gland is directly against
a shallow impression on the medial side of the mandible
(submandibular fossa) inferior to the mylohyoid line; the smaller
arm of the hook (or deep part) of the gland loops around the
posterior margin of the mylohyoid muscle to enter and lie within
the floor of the oral cavity where it is lateral to the root of the
tongue on the lateral surface of the hyoglossus muscle.

The submandibular duct emerges from the medial
side of the deep part of the gland in the oral cavity
and passes forward to open on the summit of a
small sublingual papilla beside the base of
frenulum of the tongue. The lingual nerve loops
under the submandi-bular duct, crossing first the
lateral side and then the medial side of the duct, as
the nerve descends anteromedially through the
floor of the oral cavity and then ascends into the
tongue.

Sublingual glands. The sublingual glands are the smallest of the
three major paired salivary glands. Each is almond shaped and
is immediately lateral to the submandibular duct and associated
lingual nerve in the floor of the oral cavity. Each sublingual gland
lies directly against the medial surface of the mandible where it
forms a shallow groove (sublingual fossa) superior to the ante-
rior one-third of the mylohyoid line. The superior margin of the
sublingual gland raises an elongate fold of mucosa (sublingual
fold), which extends from the posterolateral aspect of the floor
of the oral cavity to the sublingual papilla beside the base of the
frenulum of the tongue at the midline anteriorly. The sublingual
gland drains into the oral cavity via numerous small ducts,
which open onto the crest of the sublingual fold.

Vessels:that supply the parotid gland originate from the external
carotid artery and from its branches that are adjacent to the
gland. The submandibular and sublingual glands are supplied by
branches of the facial and lingual arteries. Veins from the
parotid gland drain into the external jugular vein, and those
from the submandibular and sublingual glands drain into lingual
and facial veins. Lymphatic vessels from the parotid gland drain
into nodes that are on or in the gland. These parotid nodes then
drain into superficial and deep cervical nodes. Lymphatics from
the submandibular and sublingual glands drain mainly into
submandibular nodes and then into deep cervical nodes,
particularly the juguloomohyoid node.

Innervation - Parasympathetic innervation to all
salivary gland in the oral cavity is by branches of
the facial nerve, which join branches of the
maxillary [V2] and mandibular [V3] nerves to
reach their target destinations. The parotid gland,
receives its parasympathetic innervation from
fibers that initially travelled in the glossopharyn-
geal nerve [IX], which eventually joins a branch of
the mandibular nerve [V3] in the infratemporal
fossa

This fossa is located in the posterosuperior part of the
vertebral column and the base of the skull. It is situated at the
back of the lower part if the head and the upper part of the neck.
Superomedial boundary is formed by rectus capitis posterior
major supplemented by rectus capitis minor. Superolateral
boundary is formed by superior obliquus muscle, and the
inferiorlateral boundary is formed by inferior obliquus muscle.
Roof is formed by: Splenius capitis, semispinalis capitis,
longissimus capitis and semispinalis cervcis. Roof is crossed by
greater occipital nerve which winds the lower border of inferior
oblique muscle. Floor : is formed by the posterior arch of the
atlas and the atlanto-occipital membrane.

Contents: Contents are – the vertebral artery, venous
plexus and the dorsal ramus of the first cervical
nerve. Dorsal Ramus of the first cervical nerve: It
enters the triangle by passing between the posterior
arch of the atlas and the vertebral artery, and soon
breaks into numbers of branches. There are five
muscular branches give to:
• 2 recti rectus capitis posterior major and minor
• 2 obliquae obliquus superior and inferior
Splenius capitis
• Communicating to greater occipital nerve

• Sometimes a cutaneous filament.
❖The communicating branch to the greater occipital
nerve arises from the nerve to the inferior oblique muscle.
The cutaneous branch of it has to follow the occipital
artery in order to supply the skin of the occiput.
❖ Vertebral Artery: Third part of the vertebral artery lies
in the suboccipital triangle. After its exit from the foramen
of the transverse process of the atlas it runs backward
and medially to occupy the groove of the posterior arch of
the atlas. Soon it disappears under the posterior atlanto-
occipital membrane. As it leaves the triangle, it pierces the
dura-mater and enters the vertebral canal.

The facial vein is the major
vein draining the face . Its
point of origin is near the
medial corner of the orbit as
the supratrochlear and supra-
orbital veins come together to
form the angular vein. This
vein becomes the facial vein
as it proceeds inferiorly and
assumes a position just posterior to the facial artery. The facial
vein descends across the face with the facial artery until it
reaches the inferior border of the mandible.

Here the artery and vein
part company and the
facial vein passes
superficial to the
submandibular gland to
enter the internal jugular
vein. Throughout its
course the facial vein
receives tributaries from veins draining the eyelids,
external nose, lips, cheek, and chin that accompany the
various branches of the facial artery

Superficial temporal vv
Supratrochlear v.
Nasofrontal v.
Angular v.
Infraorbital v.
Facial v.
Submental v.
Anterior jugular v.
Left brachiocephalic v.
Lymph vessels joining to
form
thoracic duct
Occipital v.
Suboccipital venous
plexus
Internal jugular v.
Pterygoid plexus
Retromandibular v.
Deep cervical v.
External jugular v.
Transverse cervical v.
Suprascapular v.
Subclavian v.
Extracranial Veins

Olfactory tract (I)
Optic chiasm (II)
Oculomotor nerve (III)
Trochlear nerve (IV)
Trigeminal nerve (V)
Abducent nerve (VI)
Facial nerve (VII)
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Vestibulocochlear nerve (VIII)
Vagus nerve (X)
Accessory nerve (XI)

Olfactory
mucosa
Olfactory
bulb
Cribriform
plate
Olfactory
tract
Ant. Perf. Subs.
Piriform lobe
Amygdaloid body
(phantom) Uncus
Dentate gyrus
Parahippo-
campal
gyrus
THE OLFACTORY NERVE (I)
The central processes of the
olfactory receptors pass
superiorly from the olfactory
mucosa in the upper part of the
superior nasal concha, through
the cribriform plate of the
ethmoid bone to end by
synapsing with the dendrites of
mitral cells in the olfactory
bulb and terminate in the
cortex of the uncus, the
adjacent infero-medial
temporal cortex and the region
of the ant. Perf. subs.

The optic nerve is the nerve of
vision Devoid of neurilemmal
sheaths, its fibres, like other brain
tissues, are incapable of
regeneration after division. From all
parts of the retina these axons
converge on the optic disc whence
they pierce the sclera to form the
optic nerve. The optic nerve passes
posteromedially to the optic foramen
through which it reaches the optic
groove on the dorsum of the body of
the sphenoid.

Here, all the fibres from the medial
half of the retina (temporal visual
field) cross over in the optic chiasma
to the optic tract of the opposite side,
while the fibres from the lateral half
of the retina (nasal visual field) pass
back in the optic tract of the same
side.
. The great majority of the fibres
in the optic tract end in the six-
layered LGB of the thalamus, but a
small proportion, bypass the LGB to
reach the superior colliculus and
pretectal area

From the LGB the fibres of the optic
radiation sweep laterally, and some
forwards into the temporal lobe
before passing posteriorly to the
occipital visual cortex where they
terminate in such a way that the
upper and lower halves of the retina
are represented on the upper and
lower lips of the fissure respectively

It supplies most of the extrinsic eye
muscles and conveys the pregan-
glionic parasympathetic fibres for the
sphincter of the pupil via the ciliary
ganglion. Its nucleus of origin lies in
the floor of the cerebral aqueduct at
the level of the superior colliculus and
consists essentially of two parts: the
somatic efferent nucleus, supplying
the ocular muscles, and the Edinger–
Westphal nucleus from which the
preganglionic parasympathetic fibres
are derived.

The most slender of the cranial
nerves and supplies only one eye
muscle, the superior oblique. Its
nucleus of origin lies in a similar
position to that of the 3rd nerve at
the level of the inferior colliculus, but
from here its fibres pass dorsally
around the cerebral aqueduct and
decussate in the superior medullary
vellum Emerging on the dorsum of
the pons (being the only cranial
nerve to arise from the dorsal aspect
of the brainstem)

The nerve winds round the cerebral
peduncle and then passes forwards
between the superior cerebellar and
posterior cerebral arteries to pierce
the dura. It then runs anteriorly in
the lateral wall of the cavernous
sinus between the oculomotor and
ophthalmic nerves to enter the orbit
through the superior orbital fissure,
lateral to the tendinous ring from
which the recti take origin. It then
passes medially over the optic nerve
to enter the superior oblique muscle.

As the name suggests, this nerve
consists of three divisions.
Together they supply sensory
fibres to the greater part of the
skin of the head and face, the
mucous membranes of the mouth,
nose and paranasal air sinuses and,
by way of a small motor root, the
muscles of mastication. In addition
it is associated with four autonomic
ganglia, the ciliary, pterygopalatine,
otic and submandibular.

Abducent nerve also supplies only one
eye muscle, the lateral rectus. Its
nucleus lies in the caudal part of the
pons and from there its fibres pass
through the pontine tegmentum to
emerge on the base of the brain at the
junction of the pons and medulla. The
nerve then passes forwards to enter the
cavernous sinus. Here it lies lateral to
the internal carotid artery and medial to
the 3rd, 4th and 5th nerves. Passing
through the tendinous ring just below the
3rd nerve, it enters the orbit to pierce
the deep surface of the lateral rectus.

In addition to supplying the
muscles of facial expression,
the facial nerve conveys
secretomotor fibres to the
sublingual and
submandibular salivary
glands and the lacrimal
gland as well as the nasal
mucosa; it also carries taste
fibres from the anterior
two-thirds of the tongue.

The fibres innervating the
facial muscles have their
nucleus of origin in the
ventral part of the caudal
pons; the secretomotor
fibres for the salivary glands
are derived from the
superior salivary nucleus.
The sensory fibres associated
with the nerve have their
cells of origin in the facial
(geniculate) ganglion.

On emerging from the
stylomastoid foramen, the
nerve supplies the stylohyoid
and the posterior belly of
digastric muscle. It then enters
the parotid gland where it
divides into five divisions for
the supply of the facial
muscles: the temporal,
zygomatic, buccal, mandibular,
and cervical branches.

The 8th nerve consists of two sets
of fibres: cochlear and vestibular.
The cochlear fibres (concerned with
hearing) represent the central
processes of the bipolar spiral
ganglion cells of the cochlea which
traverse the internal auditory
meatus to reach the lateral aspect
of the medulla, at the cerebello-
pontine angle (together with VII),
where they terminate in the dorsal
and ventral cochlear nuclei.

It contains sensory fibres for the
pharynx and the posterior one-third of
the tongue (including the taste buds),
motor fibres for the stylopharyngeus
muscle and secretomotor fibres for the
parotid gland. It is attached to the upper
part of the medulla by four or five
rootlets along the groove between the
olive and the inferior cerebellar
peduncle and leaves the skull by way of
the jugular foramen in which it gives off
its tympanic branch.

It has the most extensive distribution
of all the cranial nerves, innervating
the heart and the major part of the
respiratory and alimentary tracts.
Central connections
The dorsal nucleus of the vagus in the
medulla is a mixed visceral afferent
and efferent nucleus. It receives
sensory fibres from the heart, the
lower respiratory tract and the
alimentary tract down to the
transverse colon.

It is conventionally described as having
a cranial and a spinal root. According to
standard descriptions, the cranial root
is formed by a series of rootlets that
emerge from the medulla between the
olive and the inferior cerebellar
peduncle. These rootlets are considered
to join the spinal root, travel with it
briefly, then separate within the jugular
foramen and are distributed with the
vagus nerve to supply the musculature
of the palate, pharynx and larynx.

The hypoglossal nerve is entirely
motor and supplies all the
intrinsic and extrinsic muscles of
the tongue (with the exception
of the palatoglossus). From its
nucleus, which lies in the floor
of the 4th ventricle , a series of
about a dozen rootlets leave the
side of the medulla in the
groove between the pyramid
and the olive.

Spinal nerves
SPINAL CORD. Medulla spinalis. Consists of
the myelin-rich white matter and the myelin-
poor gray matter. It extends from the
caudal end of the medulla oblongata, near
the exit of the first spinal nerves, to the
beginning of the filum terminale at L1−2.
Cervical enlargement. Intumescentia
cervicalis. Enlargement of the spinal cord
from C3 to T2 owing to the larger supply
region for the arms.

Spinal nerves
Lumbosacral enlargement (Intumescentia
lumbosacralis). Expansion of the spinal cord from
T9−10 to L1−2 caused by the greater supply
region for the lower limbs. Conus medullaris.
Tapered termination of the spinal cord at the level
of L1−2 where it becomes continuous with the
filum terminale (spinale) which is a thin terminal
prolongation of spinal cord attached inferiorly to
the posterior surface of the coccyx. Terminal
ventricle (Ventriculus terminalis). Enlargement of
the central canal at the end of the conus
medullaris.

SPINAL CORD (TRANSVERSE SECTION)
Posterior horn
Anterior horn
lateral horn
Anterior median fissure. Deep
longitudinal fissure along the
anterior aspect of the spinal cord.
Posterior median sulcus. Median
longitudinal groove between the
right and left posterior funiculi.
Posterior median septum.
Thickening of the subarachnoid
connective tissue within the
posterior median sulcus, less in the
cervical region, more in the
thoracic segment.

SPINAL CORD (TRANSVERSE SECTION)
Posterior horn
Anterior horn
lateral horn
Anterolateral sulcus. Shallow furrow
occasionally present at the exit of the
ventral root fibers. Postero-lateral
sulcus. Longitudinal groove external to
the boundary between the lateral and
posterior funiculi. It marks the site of
entry of the dorsal spinal nerve roots.
Posterior inter-mediate sulcus.
Shallow longitudinal fissure on both
sides of the median sulcus. Externally
it marks the boundary between the
funiculi gracilis and cuneatus.

THE MEMBRANES OF THE BRAIN (THE MENINGES)
The three membranes surrounding the spinal cord, the
dura mater, arachnoid mater and pia mater, are
continued upwards as coverings to the brain.
The dura is a dense membrane which, within the
cranium, is made up of two layers.
The outer layer is intimately adherent to the skull; the
inner layer is united to the outer layer except where
separated by the great dural venous sinuses and where
it projects to form four sheets.

THE MEMBRANES OF THE BRAIN (THE MENINGES)
• the falx cerebri; the falx cerebelli;
• the tentorium cerebelli; the diaphragma sellae.
The arachnoid is a delicate membrane separated from
the dura by the potential subdural space. It projects
only into the longitudinal fissure and the stem of the
lateral fissure.
The pia is closely moulded to the outline of the brain; it
dips down into the cerebral sulci leaving the
subarachnoid space between it and the arachnoid. This
space is broken up by trabeculae of fine fibrous
strands and contains the cerebrospinal fluid.

The venous sinuses lie
between the layers of the dura.
They receive the venous
drainage of the brain and of
the skull (the diploic veins) and
disgorge ultimately into the
internal jugular vein. They also
communicate with the veins of
the scalp, face and neck via
emissary veins which pass
through a number of the
foramina in the skull.

The superior sagittal sinus
lies along the attached edge
of the falx cerebri and ends
posteriorly (usually) in the
right transverse sinus.
Connecting with it are a
number of venous lakes
(lacunae laterales) into which
project the Pacchionian
bodies of arachnoid, filtering
cerebrospinal fluid (C.S.F.)
back into the blood.

The inferior sagittal sinus lies
in the free margin of the falx
cerebri and opens into the
straight sinus.
The straight sinus lies in the
tentorium cerebelli along the
attachment of the falx cerebri.
It is formed by the junction of
the great cerebral vein of
Galen with the inferior sagittal
sinus and runs backwards to
open usually) into the left
transverse sinus.

The transverse sinuses
commence at the internal
occipital protuberance and
run in the tentorium cerebelli
on either side along its
attached margin.
On reaching the mastoid part
of the temporal bone each
passes downwards, forwards
and medially as the sigmoid
sinus to emerge through the
jugular foramen as the
internal jugular vein.

The cavernous sinuses lie
one on either side of the
body of the sphenoid
against the fibrous wall of
the pituitary fossa and
rest inferiorly on the
greater sphenoid wing.
They communicate freely
with each other via the
intercavernous sinuses.

Traversing the cavernous
sinus are the carotid artery
and the cranial nerves III, IV, V
(ophthalmic and maxillary
divisions) and VI. Lying above
the cavernous sinus are three
important structures — the
optic tract, the uncus of the
temporal lobe of the
cerebrum and the internal
carotid artery, which first
pierces the roof of the sinus
then doubles back to lie
against it.

The ophthalmic veins drain
into the anterior aspect of
the cavernous sinus which
also links up, through these
veins, with the pterygoid
venous plexus and the
anterior facial vein. The
cavernous sinus also
receives venous drainage
from the brain (the
superficial middle cerebral
vein) and from the dura (the
sphenoparietal sinus).

Posteriorly, the
superior and
inferior petrosal
sinuses drain the
cavernous sinus into
the sigmoid sinus
and into the
commencement of
the internal jugular
vein respectively.

It is a colorless cellular fluid. It
flows through the ventricles
and into the subarachnoid
space.
1. CSF supports the central nervous
system (CNS) and protects it
against'concussive injury.
2. It transports hormones and
hormone-releasing factors.
3. It removes metabolic waste
products through absorption.

• Formation and absorption.
• CSF is formed by the choroid
plexus.
• Absorption is primarily
through the arachnoid villi
into the superior sagittal
sinus.

The composition of CSF is clinically relevant .
1. T he normal number of mononuclear cells
is less than 5u/l.
2. Red blood cells in the CSF indicate
subarachnoid hemorrhage (e.g., caused
by trauma or a ruptured berry aneurysm)
3. CSF glucose Ievels are normally 50 to
75mg/dl (66% of the blood glucose level)
Glucose levels are normal in patients with
viral meningitis and decreased in patients
with bacterial meningitis.

4. Total protein levels are normally between
15 and 45 mg/dl in the lumbar cistern.
Protein levels are increased in patients with
bacterial meningitis and normal or slightly
increased in patients with viral meningitis.
5. Normal CSF pressure in the lateral
recumbent position ranges from 80 to 180
mm H2O. Brain tumors and meningitis
elevate CSF pressure.

Spinal nerve root
Arachnoid villus
Choroid plexus
Chiasmatic cistern
Interpeduncular cistern
Cerebellomedullary cistern
Ambient cistern
Epidural veins
Arachnoid villus

Subarachnoid cisterns.
Aka.Cisternae
subarachnoideae.
Expansions of the
subarachnoid space
containing
cerebrospinal fluid.
Arachnoid villus

Cerebellomedullary cistern
(cisterna magna). Cisterna
cerebellomedullaris
(magna). Space between
the cerebellum and medulla
oblongata filled with CSF
fluid. It communicates with
the fourth ventricle by a
median aperture. It is
accessible through the
foramen magnum. B

Cisterna of lateral fossa of
cerebrum. Cisterna fossae
lateralis cerebri. Space
between the insula,
temporal, frontal and
parietal lobes. It is filled
with CSF and is accessible
through the lateral sulcus.
It contains branches of
the middle cerebral and
insular arteries.

Chiasmatic cistern.
Cisterna chiasmatica.
Enlarged space around
the optic chiasma filled
with cerebrospinal
fluid.

Interpeduncular cistern.
Cisterna interpeduncularis.
Space situated behind the
chiasmatic cistern and
bordered laterally by the
temporal lobe and the
cerebral crura. It is filled
with CSFand contains the
oculomotor nerve, branches
of the basilar artery, the
origin of the superior
cerebellar artery and the
posterior cerebral artery.

Ambient cistern. Cisterna
ambiens. Enlarged
cerebrospinal fluid-filled
space lateral to the
cerebral crus. It contains
the posterior cerebral
artery, superior cerebellar
artery, basal vein
(Rosenthal’s) and the
trochlear nerve.

Cisterna pericallosa. Space
filled with cerebrospinal
fluid along the corpus
callosum.
Pontocerebellar cistern.
Cisterna pontocerebellaris.
Expanded space in the
cerebellopontine angle
filled with cerebrospinal
fluid. It communicates with
the 4th ventricle by a lateral
aperture.

Arachnoid granulations.
Granulationes arachnoideae.
Avascular, villous-like
outpocketings of the
subarachnoid space into the
sagittal sinus and diploic
veins. They are more
pronounced after the tenth
year of life and are
concerned in the excretion
of cerebrospinal fluid.
Arachnoid villus

MENINGES. Connective tissue sheaths surrounding the central nervous
system: dura mater, arachnoid and pia mater. Cranial dura mater
[[Pachymeninx]]. Dura mater cranialis (encephali). Tough fibrous sheet
forming a supporting capsule for the brain and at the same time forming
the periosteum for the inner aspect of the skull. Falx cerebri. Sickle-
shaped part of the dura projecting downward into the longitudinal
cerebral fissure. Tentorium cerebelli. Dural sheet spreading out between
the ridge of the petrous part of the temporal bone and the transverse
sinus. It supports the occipital lobes. Tentorial notch. Opening in the
tentorium cerebelli for passage of the brainstem. Falx cerebelli. Small,
sickle-shaped dural sheet between the right and left cerebellar
hemispheres.

Diaphragma sellae. Small horizontal sheet of dura spreading out
between the clinoid processes above the hypophysis. Cavitas
trigeminalis . Outpocketing of the dura enclosing the trigeminal
ganglion. Subdural space. Spatium subdurale. Capillary space
between the dura and arachnoid. It may be distended, for
example, due to hemorrhage. Spinal dura mater. Dura mater
spinalis. It is separated from the wall of the vertebral canal by
an epidural space. External filum terminale. Filum terminale
externum (durale). Filamentous end of the dura mater fused
with the filum terminale. It extends from S2−3 to Co 2. Epidural
space. Spatium epidurale (peridurale). Space between the spinal
dura mater and the wall of the vertebral canal. It is filled with fat
and venous plexuses.

• Cranial arachnoid. Arachnoidea mater cranialis (encephali). Thin,
avascular membrane attaching to the cranial dura only by surface
adhesion and communicating with the pia mater by connective tissue
fibers. Subarachnoid space. Spatium subarachnoideum. Space between
flat portion of arachnoid and pia mater. It is filled with arachnoidal
connective tissue fibers and cerebrospinal fluid. Cerebrospinal fluid.
Liquor cerebrospinalis. Protein-poor fluid secreted by the choroid
plexus with a cell content of 2−6 per mm. It flows into the subarachnoid
space through openings in the fourth ventricle. Subarachnoid cisterns.
Cisternae subarachnoideae. Expansions of the subarachnoid space
containing cerebrospinal fluid.

Cerebellomedullary cistern (cisterna magna). Cisterna
cerebellomedullaris (magna). Space between the cerebellum and medulla
oblongata filled with cerebrospinal fluid. It communicates with the fourth
ventricle by a median aperture. It is accessible through the foramen
magnum. Cisterna of lateral fossa of cerebrum. Cisterna fossae lateralis
cerebri. Space between the insula, temporal, frontal and parietal lobes. It
is filled with cerebrospinal fluid and is accessible through the lateral
sulcus. It contains branches of the middle cerebral and insular arteries.
Chiasmatic cistern. Cisterna chiasmatica. Enlarged space around the
optic chiasma filled with cerebrospinal fluid. Interpeduncular cistern.
Cisterna interpeduncularis. Space situated behind the chiasmatic cistern
and bordered laterally by the temporal lobe and the cerebral crura. It is
filled with cerebrospinal fluid and contains the oculomotor nerve,
branches of the basilar artery, the origin of the superior cerebellar
artery and the posterior cerebral artery.

Ambient cistern. Cisterna ambiens. Enlarged cerebrospinal
fluid-filled space lateral to the cerebral crus. It contains the
posterior cerebral artery, superior cerebellar artery, basal
vein (Rosenthal’s) and the trochlear nerve. Cisterna pericallosa.
Space filled with cerebrospinal fluid along the corpus callosum.
Pontocerebellar cistern. Cisterna pontocerebellaris. Expanded
space in the cerebellopontine angle filled with cerebrospinal
fluid. It communicates with the 4th ventricle by a lateral
aperture. Arachnoid granulations. Granulationes arachnoideae.
Avascular, villous-like outpocketings of the subarachnoid space
into the sagittal sinus and diploic veins. They are more
pronounced after the tenth year of life and are concerned in the
excretion of cerebrospinal fluid.

bellar a.
l
es
.
oidal a.
cating segment)
bellar a.
l
Basilar a.
Posterior communicating a.
Bifurcation of Basilar a.
Posterior cerebral a.
Recurrent a.
Of Heubner
Anterior communicating a.

Anterior communicating
Anterior cerebral
Middle cerebral
Ophthalmic
Superior cerebellar
Posterior communicating
Posterior cerebral
Basilar
Ant. inferior cerebellar
Post. inferior cerebellar
Vertebral
Anterior spinal

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