L12: Osteology and radiographic appearance of the skull

Question 1

What forms the viscerocranium (facial skeleton)?

Answer 1

• zygomatic (pair)
• maxilla (central, upper teeth housed here)
• nasal bones
• lacrimal
• mandible

Question 2

Whats the imaging of choice for a facial fracture?

Answer 2

X-Ray

Question 3

What bone is very tough in the viscerocranium?

Answer 3

Supraorbital ridge

-so skin will usually just split

Question 4

Which bone in the viscerocranium is rare to fracture?

Answer 4

Maxilla

-could fall backwards and cause airway occlusion

Question 5

What bone fractrues in the viscerocranium are common?

Answer 5

Fractures of the:
-nasal bones
-zygomatic bone and arch
2 bones above are prominent so easily fractured
-mandible

Question 6

What is an OPG?

Answer 6

Orthopantomogram

-special X-Ray to image the extent of the mandible giving a streched out appearance of the mandible

Question 7

What is the temporomandibular joint?

Answer 7

Articulation between the temporal bone and mandible

-hinge type joint divided into 2 synovial cavities by fibrocartilaginous disc

Question 8

What are some conditions associated with the temporomandibular joint?

Answer 8

TMJ disorder:
Pain felt in and around the temporomandibular joint and often refers up to ear, jaw, lateral side of the head
-problems with clicking and locking

Dislocation
Arthritis

Question 9

What is the innervation of the TMJ?

Answer 9

Auriculotemporal nerve (branch of the mandibular division of the trigeminal)
-sensory nerve (but this also supplies skin to ear, head, jaw, hence the pain radiating)

Question 10

What is the anatomy of the TMJ?

Answer 10

• Articulation between the mandibular condyle and temporal bone (mandibular fossa and articular tubercle)
• don’t articulate directly, as they are separated by fibrocartilginous disc creating a superior and inferior part of the joint cavity
• superior and inferior joint capsule

Question 11

What are the movements of the TMJ?

Answer 11

Inferior joint capsule
-rotation (opening and closing of jaw-hinge)
Superior joint capsule
-gliding (forwards and backwards: condyle slides onto articular tubercle)

Question 12

What are the movements of the mandible at the TMJ?

Answer 12

Elevation: masseter, temporalis, medial pterygoid
Depression: lateral pterygoid, gravity (against resistance: platysma, suprahyoids)
Protraction: lateral pterygoid, medial pterygoid (assists)
Retraction: posterior fibres of the temporalis
Grinding: muscles of two sides working together

Question 13

How does the TMJ dislocate?

Answer 13

Caused by trauma to side of jaw/yawning
-when the condyle process of the mandible slides part the articular tubercle
After dislocation, the jaw locks in an open position due to anterior dislocation of condyle over articular tubercle
Contraction of muscles around joint keep it locked

Question 14

How do you retract a dislocated TMJ?

Answer 14

• push down on jaw to relax muscles

- push and slide condyle backwards into the mandibular fossa

Question 15

What bones form the zygomatic arch?

Answer 15

Zygoma (temporal process)
Temporal bone (zygomatic process)