Osteology

Question 1

Define neurocranium (1)

Answer 1

Made up of the crania/vault, the cranial floor and the cranial cavity.

Question 2

Describe the differences in the formation of the vault and cranial floor. (2)

Answer 2

Vault is made by membranous ossification, floor is made by endochondrial ossification. Not all fused when born.

Question 3

Define fontanelles and their purpose. (2)
Describe when they fuse, and what occurs if this goes wrong. (3)
Explain one clinical use of fontanelles. (2)

Answer 3

Areas of membrane that exist between skull bones which have not fused at birth.
They allow for change of head shape on birth of child, and growth of infant brain.
Anterior fuses 18-24 months, posterior 1-3 months. If this occurs too early, called craniosyntosis.
Anterior fontanelle can be used as a marker of intracranial pressure and hydration status of the infant because they can flex and move with the pressure changes.

Question 4

Explain the structure of bones of the calvaria. (3)

Answer 4

Compact bone > diploe (spongy bone > compact bone. This is there to have bone marrow in the spongy bone, add strength, and add lightness.

Question 5

Describe the signs seen in an anterior cranial fossa fracture. (2)

Answer 5

CSF rhinorrhoea - cribriform plate #

Periorbital ecchymosis - raccoon eyes - frontal bone #

Question 6

Describe the signs seen in a posterior cranial fossa fracture. (3)

Answer 6

Haemotympanum
CSF or blood leak from external auditory meatus.
Battle’s sign - bruising behind the ear.

Question 7

What exits the superior orbital fissure?

Answer 7

Occulomotor III, trochlear IV, Trigeminal opthalmic Va, abducens VI.

Question 8

What exits the hyperglossal canal?

Answer 8

Hypoglossal XII

Question 9

What exits the cribriform foramina?

Answer 9

Olfactory I

Question 10

What exits the internal auditory meatus?

Answer 10

Facial VII, vestibulocochlear VIII.

Question 11

What exits the jugular foramen?

Answer 11

Glossopharyngeal IX, vagus X, accessory XI.

Question 12

What exits the foramen rotundum?

Answer 12

Trigeminal maxillary Vb.

Question 13

What exits the foramen ovale?

Answer 13

Trigeminal mandibular Vc.

Question 14

What exits the optic canal?

Answer 14

Optic II

Question 15

What are the sella turcica and hypophyseal fossa?

Answer 15

Sella turcica - where the pituitary gland sits.

Fossa - where the cavernous sinus sits.

Question 16

What exits the foramen spinosum?

Answer 16

Middle meningeal artery.

Question 17

What exits the carotid canal?

Answer 17

Carotid artery.

Question 18

What exits the foramen lacerum?

Answer 18

Nothing - not a real hole, filled in with cartilage - carotid artery runs over it.

Question 19

What exits the stylomastoid foramen?

Answer 19

Facial nerve emerges between styloid and mastoid processes.

Question 20

What exits the infra-orbital foramen?

Answer 20

Infra-orbital nerve of Vb.

Question 21

What exits the mental foramen?

Answer 21

Mental nerve.- inferior alveolar nerve of Vc.

Question 22

Describe the movements of the temporomandibular joint and the muscles that perform them. (8)

Answer 22

Elevation - masseter, temporalis, medial pterygoid.
Depression - lateral pterygoid (platysma and suprahypids)
Protrusion - lateral and medial pterygoid.
Retraction - temporalis.

Question 23

Describe three common conditions of the TMJ. (5)

Answer 23

Dislocation - anterior dislocation of the condyle over the articulations tubercle.
TMJ disorder - pain, clicking, locking of the jaw.
Arthritis.