2. Osteology

Question 1

What makes up the neurocraqnium? What does each begin as?

Answer 1

Calvaria - begins as membranes (intramembranous ossification occurs).
Cranial floor - begins as cartilage (endochondrial ossification occurs).
Cranial cavity.

Question 2

What makes up the viscerocranium? What do these bones begin as?

Answer 2

Facial skeleton.
Jaw.
Both begin as membranes or cartilage and ossify.

Question 3

What is the role of foramina, fissures and canals?

Answer 3

Permit cranial nerves and blood vessels to leave or reach the brain and brain stem from structures of the face and neck that they innervate.

Question 4

What are the names of the 3 bowl-shaped depressions that form the cranial floor?

Answer 4

Anterior, middle and posterior cranial fossae.

Question 5

What is the benefit of the bones of the calvaria having a trilaminar arrangement?

Answer 5

Confers protective strength without adding significant weight

Question 6

What are the 3 layers in a cross section from the outside to the inside of a bone of the calvaria? What type of bone are each?

Answer 6

Outer table - compact bone.
Diploeic cavity - spongy bone.
Inner table - compact bone.

Question 7

What are sutures?

Answer 7

Intersections between bones of the skull. They are fibrous joints.

Question 8

Why are the edges of bones forming suture joints serrated?

Answer 8

Prevents slippage and movement.

Question 9

When does growth at sutures stop?

Answer 9

At puberty

Question 10

What covers the outer table of bone, is strongly adhered at the suture line, but continuous through to the converging of the inner table?

Answer 10

Periosteum

Question 11

What type of haematoma cannot pass the suture lines and so cannot pass intercranially as it occurs between the skull and periosteum?

Answer 11

Cephalohaematoma

Question 12

What are fontanelles?

Answer 12

Large areas of unossified membranous gaps between flat bones of the calvaria.

Question 13

What are the 2 main purposes of fontanelles?

Answer 13

Allow for alteration of the skull size and shape during childbirth, and permit growth of the infant brain.

Question 14

What is craniosyntosis?

Answer 14

Early fusion of fontanelles and sutures

Question 15

When do the anterior and posterior fontanelles fuse?

Answer 15

Anterior - 18 months to 2 years.

Posterior - 1-3 months.

Question 16

Inspection and gentle palpitation of which fontanelles can be used to assess intracranial pressure and state of hydration?

Answer 16

Anterior fontanelle.

Question 17

What is the main concern when there is a skull fracture? Therefore what should be performed to rule out this?

Answer 17

Main concern - risk of intracranial injury (this can occur without a skull fracture too).
Ct scanning.

Question 18

What are the 2 main skull fracture types?

Answer 18

Linear - pass the full thickness of the skull, fairly straight, involve no bone displacement.
Depressed - fragment is displaced inwards towards the brain.

Question 19

What are fractures involving the cranial base? What are they associated with?

Answer 19

Basilar skull fractures - associated with cranial nerve injuries and prone to causing cerebrospinal fluid leaks.

Question 20

What is the thinnest area of the skull and therefore relatively easy to fracture?

Answer 20

Pterion

Question 21

What blood vessel underlies the pterion? Therefore what can a fracture to this area cause?

Answer 21

Middle meningeal artery.

Intracranial haemorrhage.

Question 22

What rare type of skull fracture can lead to raccoon eyes, battle sign and haemotimperim?

Answer 22

Basilar skull fractures

Question 23

Why does a blow to the supraorbital ridge and the supra ciliary arch tend not to cause a fracture? What happens instead?

Answer 23

Very tough bone, so the skin splits instead.

Question 24

What 3 areas of the skull are fractures common in?

Answer 24

Nasal bones, zygomatic bone and arch, and mandible.