The Skull & Cranial Cavity• Brain• Meninges• Cranial nerves• Arterial supply• Venous sinuses

30 March 2009Dr Frank CT Voon

Temporal

Occipital

Parietal

Ethmoid

Sphenoid

Frontal

• Tip: PETS OF or FPOETS.

The Neurocranium

The Cranium

• The cranium (skull) is the skeleton of the head.

• It consists of a neurocranium and a viscerocranium.

• The neurocranium is also known as the cranial vault.

• The viscerocranium is also known as the facial skeleton.

The Neurocranium

• The neurocranium (cranial vault) has a roof and a floor.

• The roof (calvaria or skull cap) is shaped like a dome.

• The basicranium (cranial base) forms the floor.

• It encloses the cranial cavity.

The Neurocranium• It is formed by 8 bones, the frontal, parietal,

occipital, temporal, ethmoidal and sphenoidal bones.

• The frontal, occipital, ethmoidal and sphenoidal bones are single and thus are in the midline.

• The parietal and temporal bones are bilateral and hence are paired.

• The fibrous joints between the bones are known as sutures.

Intramembranous ossification

• The frontal, parietal and temporal bones are formed by intramembranous ossification and are known as flat bones.

• Do note that these flat bones forming the calvaria are actually curved, with a convex external surface and a concave internal surface.

Endochondral ossification

• The sphenoid, ethmoid and temporal bones are mainly formed by endochondral ossification and are known as irregular bones.

• These bones form the cranial base.• The ethmoid is a part of both the

neurocranium and viscerocranium.

The Brain and spinal cord

• Cerebral hemispheres• Diencephalon• Midbrain• Pons and cerebellum• Medulla oblongata• Spinal cord

Parietal lobeFrontal lobe

Occipital lobe

Temporal lobe

Motor cortex Sensory cortex

The Cranial nerves

• Olfactory• Optic• Oculomotor• Trochlear• Trigeminal• Abducens

• Facial• Vestibulocochlear• Glossopharyngeal• Vagus• Accessory• Hypoglossal

The 12 cranial nerves

Foramina

• Structures that pass through the foramina• Cranial nerves• Arteries - Internal carotid and vertebral• Veins – sigmoid sinus and beginning of

internal jugular vein• Spinal cord – Foramen magnum

Anterior cerebral artery

Anterior communicating artery

Internal carotid artery

Middle cerebral artery

Posterior cerebral artery

Vertebral artery

Pontine arteries

Posterior communicating artery

Superior cerebellar artery

Anterior inferior cerebellar artery

Basilar artery

Anterior choroidal artery

Ophthalmic artery

Perforating arteries

Circle of Willis

The flow of CSF

Superior sagittal sinus

White matter

Gray matter

Falx cerebri

SkinClose tissue

AponeurosisLoose tissue

Endosteum

Periosteum

Diploe

Pia mater

Arachnoid mater

Dura mater

Outer table

Inner table

Subdural space

Subarachnoidspace

Cerebrospinal fluid

Arachnoid granulationsEmissary veins

Venous sinusesSuperior Sagittal Sinus

Inferior Sagittal Sinus

Straight Sinus

Tran

sver

se S

inus

Sigmoid

Cavernous Sinus

Superior Petrosal Sinus

InferiorPetrosalSinus

Occ

ipita

l Sin

us

Jugular foramen

Confluence

Internal occipital protruberance

Internal Jugular Vein

Sinus

The Scalp and Cranial Cavity• Skin• Close subcutaneous tissue• Aponeurosis• Loose areolar tissue• Periosteum

• Outer table• Diploe• Inner table• Endosteum • Endosteal layer of dura mater

• Menigeal layer of dura mater• Arachnoid mater• Pia mater • Brain

• Grey matter• White matter• Ventricles

Meninges and spaces– Extradural space

• Dura mater– Subdural space

• Arachnoid mater – Subarachnoid space

• Pia mater– Gray matter– White matter– Ventricles