The Skull 3 pdf - D. Firas

THE SKULL

(3)

Dr. Firas Al-Hameed

M.B.CH.B C.A.B.S MRCS(ENT)(England)

Thi-Qar Medical School

Face

(Viscerocranium)

• Determine our facial appearance.
• 14 individual bones
• Bones fuse to house the orbits of the eyes, nasal

and oral cavities, as well as the sinuses.

• The facial bones are:

• Zygomatic (2) – Forms the cheek bones of the face.

• Lacrimal (2) – The smallest bones of the face. They

form part of the medial wall of the orbit.

• Nasal (2)

• Inferior nasal conchae (2) – Located within the nasal

cavity.

• Palatine (2) – Situated at the rear of oral cavity, and

forms part of the hard palate.

• Maxilla (2) – Comprises part of the upper jaw and hard

palate.

• Vomer – Forms the posterior aspect of the nasal

septum.

• Mandible (jaw bone)

The maxilla

• Also known as the upper jaw.

This bone consists of five major parts:

• Body of the maxilla

• It contains the maxillary sinuses and contributes to

the floor of the orbit

• Infraorbital rim

• Infraorbital foramen

• Alveolar process

: forms the maxillary dental arch.

• Frontal process

: forms the medial border of the orbit.

• Zygomatic process

: contributes to the zygomatic arch

together with the zygomatic bone.

• Palatine process

: constitutes the roof of the mouth and

floor of the nasal cavity.

• Incisive foramen( nasopalatine/ anterior palatine)

• Nasopalatine nerve

• Greater palatine artery and vein

Palatine bone

located at the back of the nasal cavity, between the

maxillae and the sphenoid. Each bone consists of a
horizontal and perpendicular plate forming an L-
shape.

Sphenopalatine notch/ foramen

from the pterygopalatine fossa into the posterior
part of the superior meatus of the nose
sphenopalatine artery and vein a branch of nasal
nerve and nasopalatine nerves.

Greater and lesser palatine foramina

Cranial fossae

• The cranial cavity is divided into three

distinct depressions

The anterior cranial fossa is the most

shallow and superior of the three cranial

fossae.
• Three bones: the frontal bone, ethmoid

bone and sphenoid bone.

• It lies superiorly over the nasal and

orbital cavities. The fossa

accommodates the anteroinferior

portions of the frontal lobes of the

brain.

Contents of anterior cranial fossa

• The cribriform plate and crista galli

• Foramina for olfactory nerve

• Anterior and posterior ethmoidal foramina

• The anterior clinoid processes serve as a place of

attachment for the tentorium cerebelli (a sheet of

dura mater that divides the cerebrum from the

cerebellum).

• The lesser wings of the sphenoid bone also

separate the anterior and middle cranial fossae.

The Middle Cranial Fossa

• Located centrally in the cranial floor.
• Butterfly shaped
• Accommodating the pituitary gland

and two lateral parts accommodating
the temporal lobes of the brain.

• Three bones – the sphenoid bone and

the two temporal bones

Foramina of the middle cranial fossa

Foramina of the Sphenoid Bone
• The

optic canals

: transmit the optic nerves

(CN II) and ophthalmic arteries into the

orbital cavities.

Immediately lateral to the central part of the

middle cranial fossa are four foramina:
• The

superior orbital fissure

opens

anteriorly into the orbit. It transmits the

oculomotor nerve (CN III), trochlear nerve

(CN IV), ophthalmic branch of the

trigeminal nerve (CN V1), abducens nerve

(CN VI), opthalmic veins and sympathetic

fibres.

• The

foramen rotundum

transmits the

maxillary branch of the trigeminal nerve

(CN V2).

• The

foramen ovale

transmits the

mandibular branch of the trigeminal nerve

(CN V3) and accessory meningeal artery.

• The

foramen spinosum

transmits the

middle meningeal artery, middle

meningeal vein and a meningeal branch of

CN V3.

Foramina of the Temporal Bone

• Carotid canal –

• located posteriorly and medially to the foramen

ovale.

• Transmits the internal carotid artery, internal

carotid venous plexus and sympathetic nerve

plexus from the neck into the cranial cavity.

• At the junction of the sphenoid, temporal and

occipital bones is the foramen lacerum.

• In life, this foramen is filled with cartilage, which

is pierced by small blood vessels

• The internal carotid artery passes from the

carotid canal in the base of the skull, emerging

and coursing superior to foramen lacerum as it

exits the carotid canal. The internal carotid

artery does not travel through foramen lacerum.

The segment of the internal carotid artery that

travels above foramen lacerum is called the

lacerum segment.

Carotid canal

The posterior cranial fossa

• The most posterior and deep of the

three cranial fossae.

• It accommodates the brainstem and

cerebellum.

• Three bones: the occipital bone and the

two temporal bones.

Foramina

Temporal Bone

• The internal acoustic meatus is an oval opening in the posterior

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

facial nerve (CN VII), vestibulocochlear nerve (CN VIII) and

labyrinthine artery.

Occipital Bone

• Foramen magnum

, lies centrally in the floor of the posterior cranial

fossa.

• It is the largest foramen in the skull. It transmits the medulla of the

brain, meninges, vertebral arteries, spinal accessory nerve

(ascending), dural veins and anterior and posterior spinal arteries.

• The

jugular foramina

are situated either side of the foramen

magnum. Each transmits the glossopharyngeal nerve, vagus nerve,

spinal accessory nerve (descending), internal jugular vein, inferior

petrosal sinus, sigmoid sinus and meningeal branches of the

ascending pharyngeal and occipital arteries.

• Hypoglossal canal

: immediately superior to the anterolateral margin

of the foramen magnum . It transmits the hypoglossal nerve

through the occipital bone.

• Posterolaterally to the foramen magnum lies the cerebellar fossae.

These are bilateral depressions that house the cerebellum. They are

divided medially by a ridge of bone, the internal occipital crest.

Jugular bulb
Inferior petrosal and sigmoid sinuses

Labyrinthine artery

Middle meningeal artery
Middle meningeal vein

Foramen spinosum
Meningeal branch of CN V3

Scalp

• S

kin

– contains numerous hair follicles and

sebaceous glands (thus a common site for

sebaceous cysts).

• Dense

onnective tissue

– connects the skin to

the epicranial aponeurosis. It is richly

vascularised and innervated.

• The blood vessels within the layer are highly adherent to

the connective tissue.

• Epicranial

poneurosis

– a thin, tendon-like

structure that connects the occipitalis and

frontalis muscles.

• L

oose Areolar Connective Tissue

– a thin

connective tissue layer.

• It contains numerous blood vessels, including emissary

veins which connect the veins of the scalp to the diploic

veins and intracranial venous sinuses.

• Danger area

• P

eriosteum

– the outer layer of the skull bones.

Scalp

• Arterial Supply

• Branches of external carotid artery and the ophthalmic

artery (a branch of the internal carotid)

• Venous Drainage

• The superficial drainage follows the arterial supply

• The deep (temporal) region of the skull is drained by

the pterygoid venous plexus. Drain into the maxillary

vein.

• The veins of the scalp

connect to the diploic veins

of the skull via valveless emissary veins

. This

establishes a connection between the scalp and the

dural venous sinuses.

• Lymphatics: posterior half: occipital and posterior

auricular nodes. Anterior: parotid nodes

• Eventually: submandibular and deep cervical nodes.

• Innervation

• The scalp receives cutaneous innervation from branches

of the trigeminal nerve or the cervical nerve roots.

تابع لمحاضره سابقه

Stylomastoid foramen:

It is located on the inferior surface of the
petrous temporal bone, between the base of
the styloid process and the mastoid process of
the temporal bone. It transmits the facial nerve
and stylomastoid artery (branch of posterior
auricular artery).