Osteology of the Head and Neck

Question 1

Broadly speaking, what 2 areas can the skull be divided into?

Answer 1

1. Neurocranium - encases brain
2. Viscerocranium- face and jaw

Question 2

How do the different types of bones of the neurocranium begin?

Answer 2

• vault bones begine as membranes → intramembranous ossification
• cranial floor/ base bones begin as cartilage → endochondrial ossification

Question 3

What can the neurocranium be divided into?

Answer 3

Calvaria and Cranial Floor

Question 4

Label the bones of the calvaria

Answer 4

Question 5

Label the sutres of the Calvaria

Answer 5

Question 6

What are fontanelles in infants?

Answer 6

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

Question 7

Why are fontanelles important?

Answer 7

• Allow for alteration of the skull in size and shape during childbirth
• Permits growth of infant brain

Question 8

At what age to fontanelles fuse?

Answer 8

Anterior - ~ 18 months

Posterior - ~ 1-3 months

Question 9

What is craniosynotosis?

Answer 9

Early fusion of fontanelles and sutres, can affect the shape of the skull and brain development

Question 10

Where are fontanelles located?

Answer 10

Anterior- site of future bregma

Posterior- site of future lambda

Question 11

How is the anterior fontanelle used to examine newborns/infants?

Answer 11

• In a healthy baby will be slightly convex
• slightly bulging = high intracranial pressure
• sunken = sign of dehydration

Question 12

How are bones of the calvaria arranged in cross section?

Answer 12

Trilaminar arrangement

2 layers of compact bone (outer and inner table) with a layer of spongy bone in between (diploe)

Question 13

What is the benefit of the trilaminar arrangement of the calvaria?

Answer 13

Confers protective stregnth without adding significant weight

Question 14

How does periosteum envelope the bones of the skull?

Answer 14

Each individual bone (including its suture lines) are wrapped with periosteum

Question 15

Label the cranial fossae of cranial floor

Answer 15

Question 16

Which bones make up the anterior cranial floor?

Answer 16

1. Frontal bone (mainly)
2. Ethmoid bone
3. Sphenoid bone

Question 17

What part of the cranial floor does the sphenoid bone make up?

Answer 17

Part of both the anterior and middle cranial floor

Question 18

What is the sella turcica?

Answer 18

A saddle like depression of the sphenoid bone where the pituitary gland sits

Question 19

Identify the bones of the cranial base

Answer 19

Question 20

Which part of the temporal bone houses middle and inner ear structures?

Answer 20

The Petrous Bone

Question 21

Identify the External Occiputal protuberance and the superior nuchal lines of the occipital bone

Answer 21

Question 22

What is the difference between linear and comminuted fractures of the cranial vault?

Answer 22

• Linear = straight with no bone displacement
• Comminuted = multiple fracture lines
  
  • may/ may not be displaced inwards (depressed/ non-depressed)

Question 23

Identify some clinical signs of a basilar skull fracture (fracture of cranial floor)

Answer 23

• Battle’s sign (bruising over mastoid process)
• Raccoon eyes (bruising around both eyes)
• Haemotympanum (blood bheind ear drum)
• CSF leaking from nose or ear

Question 24

Identify the bones of the facial skeleton

Answer 24

Question 25

What is most likely to happen in a facial injury to the supraorbital ridge of the face?

Answer 25

Bone is unlikely to fracture as frontal bone is very tough, instead skin is likely to split

Question 26

Which bones of the base are morst likely to fracture and why?

Answer 26

• Nasal bone
• Zygomatic bone and arch
• Mandible

As they are the most prominent features of the face

Question 27

What is important to look for on an x-ray of a fractured mandible?

Answer 27

The mandible will always fracture in 2 places

Question 28

What is the temporomandibular joint and what type of joint is it?

Answer 28

• The joint between the temporal bone and mandible
• TMJ is a hinge joint
  
  • 2 synovial cavities divided by fibrocartilaginous disc

Question 29

What conditions can affect the temporomandibular joint?

Answer 29

• TMJ disorder (pain, clicking and locking of the jaw)
• Dislocation
• Arthritis

Question 30

Which nerve innervates the TMJ joint?

Answer 30

The auriculotemporal nerve

(a branch of mandibular division of trigeminal)

Question 31

Identify the landmarks of the TMJ

Answer 31

Question 32

What things stabilise the TMJ?

Answer 32

• Joint capsule
• Extracapsular ligaments

Question 33

Describe the movement of the TMJ in opening the jaw (depressing the mandible)

Answer 33

1. Hinge rotation action of inferior half of joint
2. Gliding forwards of the condyle onto the articular tubercle

Question 34

Why is the jaw locked in an open position in jaw dislocation?

Answer 34

Due to the anterior dislocation of the condyle over the articular tubercle

Question 35

Give the layers of the scalp

Answer 35

• Skin
• Dense connective tissues
• Aponeurosis
• Loose connective tissue
• Periosteum

Question 36

Which kind of veins run through the loose connective tissue layer of the scaps and into dural venous sinuses?

Answer 36

Emmissary Veins

Question 37

Why may you get brusing aroud the eyes following injury to the scalp?

Answer 37

• Subaponeurotic blood vessels in loose connective tissue layer can bleed and track along underneath the margins of the aponeurosis
• anterioraly, aponeurosis continues as frontalis muscle which has no bony instertion
• Instead muscle merges with skin and subcut tissues around the orbit so blood can track and collect in orbital tissue and bridge of nose