The Skull

Question 1

What is the skull and what is it composed of? What are its two sections?

Answer 1

• The skull is composed of 22 bones. 21 bones are linked by fibrous joints. The mandible articulates via the synovial temporomandibular joint.
• Neurocranium = cranial vault
  o Protect the fragile brain
  o Attachment site for head and neck muscles
• Viscerocranium = facial skeleton
  o Form framework of the face
  o Contain cavities for special sense organs (sight, taste and smell)
  o Opening for air and food passage
  o Secure teeth
  o Anchor facial muscles of expression

Question 2

What are the 8 cranial bones?

Answer 2

-	There are 8 cranial bones;
o	Parietal (x2)
o	Temporal (x2)
o	Sphenoid
o	Frontal
o	Ethmoid
o	Occipital
(see lecture notes for diagram)

Question 3

What are the cranial sutures and what do they do?

Answer 3

Coronal suture (middle meningeal artery runs close to this)
Sagittal suture
Lambdoid suture
(see lecture notes for diagram)
Fibrous interlocking sutures unite the bones of the skull

Question 4

What are the fontanelles and what do they do?

Answer 4

• The fontanelles allow growth of the brain, and flexibility of the skull during birth. Otherwise the pressure exerted on a fully fused skull would fracture during birth.
• Sutures are particularly wide in newborn skull… to allow growth of the brain, and also flexibility of the skull during birth. Otherwise the pressure exerted on a fully fused skull would fracture during birth.

Question 5

What are the four fontanelles present at birth?

Answer 5

Anterior fontanelle
Sphenoid fontanelle (future pterion)
Posterior fontanelle
Mastoid fontanelle (future asterion)
(and metopic suture??)

Question 6

What are the features of the temporal bone?

Answer 6

See diagram in lecture notes

Question 7

What are the features of the sphenoid bone?

Answer 7

See diagram in lecture notes

Question 8

What are the meninges of the brain, and in what order are they arranged (from outside to inside)?

Answer 8

Dura mater (tough and DURAble)
Arachnoid mater
Pia Mater
(also periosteal layer and meningeal layer)

Question 9

What is the falx cerebri, tentorium cerellum and tentorial notch in the meninges?

Answer 9

• Falx cerebri runs from front bone to back of skull
• Tentorium cerebellum forms a sort of tent over the cerebellum
• Tentorial notch surrounds the midbrain

Question 10

What are the dural venous sinuses?

Answer 10

• Between the periosteal and meningeal layers of the dura mater is a network of endothelial lined spaces, which are filled with venous blood; the dural venous sinuses.

Question 11

Name the dural venous sinuses.

Answer 11

Superior sagittal sinus
Inferior sagittal sinus
Straight sinus
Transverse sinus
Cavernous sinus
Sigmoid sinus
Petrosal sinus
(and jugular foramen??)
(see lecture notes for diagrams)

Question 12

What are the facial bones and what do they do?

Answer 12

• The facial skeleton forms the anterior part of the skull and consists of the bones which surround the orbit, mouth and nasal cavities.
  (see lecture notes for diagram)

Question 13

Name all of the facial bones.

Answer 13

Zygomatic
Lacrimal
Nasal
Inferior Conchae
Vomer
Maxilla
Mandible
Palatine
(see lecture notes for diagram)

Question 14

What is the orbit and which bones contribute to it?

Answer 14

-	The orbit is a bilateral pyramidal shaped cavity on the anterior aspect of the skull. It houses the eyeball, extra-ocular muscles and  associated neurovasculature. The bones contributing to the orbit are; 
o	Frontal
o	Maxilla
o	Lacrimal
o	Ethmoid
o	Sphenoid
o	Zygomatic
(see lecture notes for diagram)

Question 15

What is the oral cavity and what is it made up of?

Answer 15

• The bony skeleton of the oral cavity is made up of the maxilla and mandible which house the upper and lower teeth respectively. The hard palate also has a contribution from the palatine bone.

Question 16

What are the components of the nasal cavity?

Answer 16

See lecture notes for diagrams

Question 17

What are the paranasal sinuses?

Answer 17

• The paranasal sinuses are hollow spaces within the frontal, sphenoid, ethmoid and maxillary bones. They are lined by mucous membrane and all drain into the nose.
  (see lecture notes for diagrams)

Question 18

What are the internal features of the cranial base?

Answer 18

Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
Lesser wing of sphenoid
Petrous temporal

Question 19

What are the three anterior cranial fossae?

Answer 19

Frontal
Ethmoid
Sphenoid

Question 20

What are the three middle cranial fossae?

Answer 20

Sphenoid
Temporal
Parietal

Question 21

What are the four posterior cranial fossae?

Answer 21

Sphenoid
Parietal
Temporal
Occipital

Question 22

What foramen does the middle meningeal artery pass through?

Answer 22

Foramen spinosum

Question 23

A blow to the middle meningeal artery would result in what sort of haematoma?

Answer 23

Extradural haematoma

Question 24

What are the three other foramina of the skull?

Answer 24

Foramen lacerum
Carotid canal
Jugular foramen
(see lecture notes for diagram)

Question 25

What are the parts of the internal carotid artery?

Answer 25

Cervical part
Petrous part
Cavernous part
Cerebral part

Question 26

What are the twelve nerves in the skull? (cranial nerves)

Answer 26

Olfactory
Optic 
Oculomotor
Trochlea
Trigeminal
Abducent
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal

Question 27

What is the olfactory nerve (I)?

Answer 27

• The olfactory nerves run inferiorly from the olfactory bulb, though the perforated cribiform plate of the ethmoid bone to enter the nasal cavity.

Question 28

What is the optic nerve (II)?

Answer 28

• The optic nerve traverses the optic canal to enter the orbit.

Question 29

What is the oculomotor nerve (III)?

Answer 29

o The oculomotor nerve emerges from the midbrain

o Along with Trochlear (IV) and Abducens (VI) traverses the superior orbital fissure to enter the orbit.

Question 30

What is the trochlear nerve (IV)?

Answer 30

The trochlear nerve emerges from the posterior surface of the midbrain
o Along with Oculomotor (III) and Abducens (VI) with traverses the superior orbital fissure to enter the orbit.

Question 31

What is the abducens nerve (VI)?

Answer 31

The abducens nerve emerges from the pons

o Along with Oculomotor (III) and Trochlear (IV) with traverses the superior orbital fissure to enter the orbit.

Question 32

What is the trigeminal nerve (V)?

Answer 32

• The trigeminal nerve emerges from the lateral surface of the pons and splits into 3 branches:
  o Opthalmic (V1)
  o Maxillary (V2)
  o Mandibular (V3)
• The ophthalmic branch traverses the superior orbital fissure to enter the orbit
• The maxillary branch leaves the cranium by passing through foramen rotundum
• The mandibular branch runs through foramen ovale

Question 33

What is the facial nerve (VII)?

Answer 33

• The facial nerve emerges from the pons, and passes through the internal acoustic meatus.
• The facial nerve runs through the petrous temporal bone and exits the skull via the stylomastoid foramen

Question 34

What is the vestibulocochlear nerve (VIII)?

Answer 34

• The vestibulocochlear nerve emerges from the pons and enters the internal acoustic meatus

Question 35

What are the glossopharyngeal (IX) and vagus nerves (X)?

Answer 35

• The glossopharyngeal nerve emerges from the lateral surface of the medulla oblongata with the vagus nerve, they both exit the skull via the jugular foramen

Question 36

What is the spinal accessory nerve (XI)?

Answer 36

• The spinal accessory emerges from the first 5-6 cervical segments and then runs superiorly through the foramen magnum then leaves the skull via the jugular foramen

Question 37

What is the hypoglossal nerve (XII)?

Answer 37

• The hypoglossal nerve emerges from the anterior aspect of the medulla oblongata and runs through the hypoglossal canal