Skull and cranial cavity

Question 1

Layers of the scalp

S C A L P

Answer 1

From superficial to deep:

S-Skin

C- Connective tissue, dense.

A- Aponeurotic layer.

• When lacerated, loses the scalp anchoring properties.
• Connects frontalis to occipitalis.

L- Loose connective tissue.
- Separates upper three layers from pericranium.

P- Pericranium

Question 2

Innervation of the scalp

Answer 2

Innervated by the trigeminal nerve (CN V) and spinal cutaneous nerves.

Question 3

Function of meninges

Answer 3

Protection of the brain.

Supports network of blood vessels.

Forms fluid filled cavity to cushion and nourish the brain.

Question 4

Dura mater

Answer 4

Outermost layer of the meninges that surrounds brain and spinal cord

Divided into two layers:

• Endosteal (outer), lines the skull.
• Meningeal (inner)

Dural sinuses forms between both layers.

Question 5

Nervous supply to the dura mater

Answer 5

CN V- trigeminal
CN X- vagus

C1-3, sympathetic supply

Question 6

Blood supply of the dura mater

• Source
• Branches

Answer 6

Middle meningeal artery
- Branch of maxillary artery

Branches into anterior and posterior middle meningeal artery.

Question 7

Meningeal layer of the dura

Answer 7

Innermost dura mater layer that folds to form septa.
- Folds helps to restrict movement of the brain

Folds:

• Falx cerebri
• Tentorium cerebelli
• Falx cerebelli

Question 8

Falx cerebri

Answer 8

A fold in the meningeal, dura mater that separates the cerebral hemispheres.

Question 9

Tentorium cerebelli

Answer 9

A fold in the meningeal, dura mater that separates the cerebral hemispheres from the cerebellar hemispheres.

Question 10

Falx cerebelli

Answer 10

A fold in the meningeal, dura matter that separates the cerebella hemispheres.

Question 11

Dura anatomical basis of headaches

Answer 11

Caused by the dura’s sensitivity to stretching.

Question 12

Extradural haematoma

Answer 12

A collection of blood between the inner skull surface and the endosteal layer of the dura mater.

Can be caused by damage to the middle meningeal artery.

Question 13

Tentorial herniation

• Mechanism
• Causes

Answer 13

When a part of the brain is squeezed through the tentorium cerebelli due to an increase in intracranial pressure.
- Herniation in temporal lobe

Increase in ICP can be caused by a space occupying lesion like a brain tumour or intracranial haemorrhage.

Question 14

Arachnoid mater

Answer 14

The middle layer of the meninges.

Avascular layer, contains projections (arachnoid granulations) to transfer CSF to venous sinuses.

Subarachnoid space contains CSF which protects brain from mechanical force.
- This is also the space where structures to and from the brain pass through.

Question 15

Layers of the meninges

Answer 15

Dura (hard) mater- outermost

Arachnoid mater- middle

Pia (soft) mater- innermost

Question 16

Cerebrospinal fluid (CSF)

Answer 16

Fluid produced by specialised ependymal cells in the choroid plexus in brain ventricles.

Found in the brain and spinal cord.
- Absorbed by arachnoid granulations in the meninges

Provides buoyancy in the subarachnoid space which protects agains mechanical force.

Question 17

Pia mater

Answer 17

Innermost, soft, layer of the meninges.

Follows the brain gyri and sulci.

Very vascular structure that forms part of the cerebral arteries entering the brain.

Question 18

Spinal cord meninges

Answer 18

3 layers that form part of the spinal nerve roots:

• Dura mater (only the meningeal layer)
• Arachnoid mater
• Pia mater

Question 19

Leptomeningitis

Answer 19

Infection and inflammation in the leptomeninges (arachnoid and pia mater).

Can cause septicaemia if infection enters subarachnoid space and consequently into the blood.

Question 20

Dural sinuses

Answer 20

Venous channels between the layers of the dura.

• Contains drained blood and CSF from the brain and cerebral veins.
• Drains into the IJV.

Communicates with the veins of the skull and scalp.

Contains no valves or SM- just a thick endothelial wall.

Question 21

Blood supply to the brain

Answer 21

Main branches:

• Internal carotid, from common carotid artery
• Vertebral artery, from subclavian.

Circle of Willis is formed from their anastomose.

Anterior and middle cerebral arteries- terminal branches

Question 22

Vertebral artery

Answer 22

Supplies the brain, branches from the subclavian.

Passes within cervical vertebrae and enters through foramen magnum.

Unites to form basilar artery.

Question 23

Circle of Willis

Answer 23

Anastomose of 2 internal carotid arteries with 2 vertebral arteries.

ICA connects to the posterior cerebral artery by the posterior communicating artery.

Anterior communicating artery connects anterior cerebral arteries together.

Question 24

Anterior cerebral artery

• Source
• Supply

Answer 24

Source- Internal carotid artery

Part of Circle of Willis

Supplies medial and superior surfaces of the brain + frontal pole

Question 25

Middle cerebral artery - Source - Supply

Answer 25

Source- internal carotid Supplies- lateral surfaces and the temporal pole.

Question 26

Posterior cerebral artery - Source - Structure - Supplu

Answer 26

Source- Basilar artery Part of Circle of Willis- connects to MCA and ICA via posterior communicating artery. Supplies- inferior surfaces and occipital pole.

Question 27

Occlusion of vertebral/ ICA

Answer 27

Causes mixing of blood in posterior communicating artery. | - Blood passes back and forth to compensate lack of blood flow.

Question 28

Neurocranium

Answer 28

The cranium, composed of 8 bones: - Frontal - Parietal x2 - Temporal x2 - Occipital - Ethmoid - Sphenoid Intra-sutural bones can appear- extra bones

Question 29

Viscerocranium

Answer 29

The facial bones: 14 - Nasal 2x - Maxilla 2x - Zygomatic 2x - Nasal conchae x2 - Palatine x2 - Lacrimal x2 - Mandible - Vomer

Question 30

Skull

Answer 30

Composed of the cranium (neurocranium) and the facial bones (viscerocranium). 22 bones in total. Protects the brain and allows attachment for muscles of the face and head.

Question 31

Cribiform plate

Answer 31

Part of the ethmoid bone Foramen in the skull that supports the olfactory bulb.

Question 32

Optic canal

Answer 32

Formed from the sphenoid bone. Passageway for: - Optic nerve - Ophthalmic artery

Question 33

Superior orbital fissure

Answer 33

Opening of the skull, in the sphenoid bone. Many structures pass through.

Question 34

Foramen rotundum

Answer 34

Opening of the skill of the sphenoid bone. Maxillary nerve of the trigeminal nerve passes through.

Question 35

Foramen ovale

Answer 35

Opening of the skull in the sphenoid bone. | - Mandibular nerve of CN V passes through.

Question 36

Foramen spinosum

Answer 36

Opening of the skull in the sphenoid bone. Passageway for: - The middle meningeal artery - Middle meningeal vein - Meningeal branch of the mandibular nerve.

Question 37

Internal acoustic meatus

Answer 37

Foramen of the temporal bone. Passageway fron CN VII and VIII (Facial and vestibulocochlear)

Question 38

Foramen magnum

Answer 38

Foramen of the occipital bone. - Passageway for CN XI (accessory) - Meninges - Medullar oblongata

Question 39

Hypoglossal canal

Answer 39

Foramen in the occipital bone Passageway for CN XII (hypoglossal)

Question 40

Jugular foramen

Answer 40

Foramen in the temporal bone. Passageway for nerves IX, X and XI (glossopharyngeal, vagus and accessory)

Question 41

Foramen lacerum

Answer 41

Foramen in the sphenoid bone Opening for the internal carotid artery.

Question 42

Stylomastoid foramen

Answer 42

Opening in the temporal bone. Passageway for facial nerve (CN VII)

Question 43

Middle meningeal artery

Answer 43

Supplies the dura mater Source: Internal maxilla artery Foramen: Foramen spinosum

Question 44

Superior sagital sinus

Answer 44

Dural sinus at the superior border of the flax cerebri

Question 45

Straight sinus

Answer 45

Dural sinus at the falx cerebri and tentorium cerebelli junction. Drains into the right and left transverse sinus Receives blood from: - Inferior sagittal sinus - Great cerebral vein

Question 46

Inferior sagittal sinus

Answer 46

Dural sinus at the inferior margin of the flax cerebri. Drains into the straight sinus.

Question 47

Transverse sinus

Answer 47

Dural sinus at the posterior and lateral attachments of the tentorium cerebelli. Drains

Question 48

Transverse sinus

Answer 48

Dural sinus at the posterior and lateral attachments of the tentorium cerebelli. Drains from confluence of sinuses and superior posterior sinus. Drains into sigmoid sinus.

Question 49

Sigmoid sinus

Answer 49

Dural sinus at the groove of the occipital, temporal and parietal bones. Drains from the transverse sinus into the internal jugular vein.

Question 50

Fontanelles

Answer 50

Soft membraneous gaps between sutures in infants. - The brain expands faster than the skull can grow. - Provides space for the brain to expand.

Question 51

Posterior fontanel

Answer 51

Also called - Lambdoid - Occipital Triangular shaped Fontanel formed at the junction between the sagittal and lambdoid suture

Question 52

Anterior fontanel

Answer 52

Also called: - Bregmatic - Frontal Diamond shaped, between the coronal and sagittal sutures. Persists until 18 months after birth. Function: - Allows the deformation of the skull during childbirth. - Expansion of the brain after birth.

Question 53

Clinical significance of fontanelles

Answer 53

Sunken fontanelles= dehydration Tense/ bulging anterior fontanelle= raised inter cranial pressure

Question 54

Sphenoidal fontanelle

Answer 54

Also called the anterolateral fontanelle Located between these bones: - Frontal - Sphenoidal - Parietal - Temporal

Question 55

Mastoid fontanelle

Answer 55

Also called the posterolateral fontanelle Located between these bones: - Temporal - Occipital - Parietal bone