2. Skull Osteology

Question 1

What are the bowl shaped depressions on the cranial floor?

Answer 1

Anterior, middle and posterior cranial fossa

Question 2

What is the anterior cranial fossa formed from?

Answer 2

Frontal bone (most of fossa)
Sphenoid bone
Ethmoid bone

Question 3

What makes up the middle cranial fossa?

Answer 3

Sphenoid bone

Temporal bone

Question 4

What makes up the posterior cranial fossa?

Answer 4

Temporal bone

Occipital bone

Question 5

What is found in the petrous part of the temporal bone?

Answer 5

Cochlea
Vestibulocochlear nerve (VIII)
Posterior semicircular canal
Anterior semicircular canal

Question 6

What is a linear fracture?

Answer 6

Fairly straight, involve not bone displacement

Question 7

What is a comminuted fracture?

Answer 7

Multiple fracture lines

Fragments may or may not displace inwards towards the brain (depressed vs non-depressed)

Question 8

Where is the weakest part of the skull bone?

Answer 8

Pterion

Question 9

What blood vessel runs directly underneath the Pterion?

Answer 9

Middle meningeal artery

Question 10

What are basilar skull fractures?

Answer 10

Fracture involving bone(s) of cranial floor

Question 11

What are the signs of a middle cranial fossa basilar fracture?

Answer 11

Blood and cerebrospinal fluid coming out of ear
Bruising behind ear (Battle’s sign)
Blood pooling in middle ear cavity

Question 12

What are the signs of an anterior cranial fossa basilar fracture?

Answer 12

Clear fluid dripping from nose

Periorbital ecchymosis

Question 13

How many bones are in the skull?

Answer 13

22

Question 14

What can the neurocranium be further split up into?

Answer 14

Calvaria (vault)
Cranial floor
Cranial cavity

Question 15

What bones form the calvaria?

Answer 15

Frontal bone
Parietal bones
Greater wing of sphenoid bone
Temporal bone
Occipital bones

Question 16

What are the joints in the calvaria?

Answer 16

Coronal suture
Sagittal suture
Lambdoid suture
Bregma (where coronal and sagittal sutures meet)
Lambda (where sagittal and lambdoid sutures meet)

Question 17

What are fontanelles?

Answer 17

Large areas of unossified membranous gaps between flat Bon of calvaria in the infant skull

Question 18

What do fontanelles allow for?

Answer 18

Alteration of skull size and shape during childbirth

Permit growth of infant brain

Question 19

When do fontanelles fuse?

Answer 19

Anterior - 18months to 2 years

Posterior - 1-3 months

Question 20

What is early fusion of fontanelles and sutures called?

Answer 20

Craniosynostosis

Question 21

What are the layers of the bones of the calvaria?

Answer 21

Compact bone (outer table)
Diploe (spongy bone)
Compact bone (inner table)

Question 22

What is the benefit of tri-laminar arrangement in bones of calvaria?

Answer 22

Confers protective strength without adding significant weight

Question 23

What are the bones of the viscerocranium?

Answer 23

Zygomatic 
Maxilla
Nasal
Lacrimal
Mandible

Question 24

What are the most common fractures in the face?

Answer 24

Nasal bones
Zygomatic bone and arch
Mandible

Question 25

What kind of joint is the temporomandibular joint?

Answer 25

Synovial hinge-type joint divided into two synovial cavities by fibrocartilaginous disc

Question 26

What are the conditions of the temporomandibular joint?

Answer 26

TMJ disorder (pain, clicking, locking) Dislocation Arthritis

Question 27

What is the temporomandibular joint innervated by?

Answer 27

Auriculotemporal nerve (branch of mandibular division of trigeminal)

Question 28

What is the TMJ stabilised by?

Answer 28

Joint capsule | Series of 3 extracapsular ligaments

Question 29

What are the movements of mandible at TMJ?

Answer 29

``` Elevation Depression Protrusion Retraction Grinding ```

Question 30

What muscles are involved in the elevation of mandible at TMJ?

Answer 30

Masseter Temporalis Medial pterygoid

Question 31

What muscles are involved in the depression of the mandible at TMJ?

Answer 31

Lateral pterygoid | Gravity

Question 32

What muscles are involved in depression of mandible?

Answer 32

Lateral pterygoid | Medial pterygoid

Question 33

What muscles are involved in retraction of mandible at TMJ?

Answer 33

Posterior fibres of temporalis

Question 34

How does dislocation of TMJ occur?

Answer 34

Facial trauma | Yawning

Question 35

What happens when the TMJ is dislocated?

Answer 35

Jaw locks as joint files in open position due to anterior dislocation of condylar over articular tubercle Contraction of muscles around joint (muscles of mastication) keep joint locked in anterior displacement