Lecture 4 - Osteology And Radiographic Appearance Of The Skull Flashcards Preview

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1

Which two structures form the skull?

The cranium and mandible

2

What can the cranium be divided into?

The neurocranium (bones that protect the brain) and viscerocranium (bones that form the facial skeleton)

3

What is the cranial cavity?

The cranial cavity is the space within the cranium, which holds the brain.

4

What does the neurocranium consist of?

The calvaria (skull cap) and cranial floor

5

What is significant about the arrangement of the bones that form the calvaria?

The bones of the calvaria consist of two layers of compact bone separated by a layer of spongy bone, known as the diploe.

This tri-lamina arrangement of compact and spongy bone conveys protective strength to the skull without adding significant weight.

6

Despite the tri-laminar arrangement fo the bones of the calvaria, severe blows to the neurocranium may still result in a skull fracture. What are the types of skull fracture secondary to trauma?

Linear
Depressed
Comminuted
Basilar (through the cranial floor)

7

What is significant about the pterion?

The pterion, which lies on the lateral aspect of the skull, is the thinnest part of the calvaria.

It is an area of clinical importance given the risk of a fracture at this site injuring the middle meningeal artery (its anterior branch), which lies immediately beneath the bone

8

What happens if there is bleeding from the middle meningeal artery?

Bleeding from this artery will cause an extradural haematoma, with blood accumulating between the periosteal layer of the dura mater and the bone.

The growing haematoma exerts pressure on the underlying brain.

9

What is the name given to the serrated, immobile joints between the flat bones forming the calvaria?

Sutures (coronal, sagittal, lambdoid)

10

What is significant about the sutures in the calvaria and what happens to them as we age?

Their interlocking nature makes it very difficult for the bones forming the joint to dislocate.

As we age, the sutures begin to ossify.

11

What is the cranial floor divided into?

The cranial floor is divided into three areas or fossae: anterior, middle and posterior.

12

Why are the boundaries of the fossa important to consider?

The boundaries and bones forming these areas are important to be aware of, as they relate closely to certain structures of the brain or areas of the skull housing the special sense organs e.g. eye, ear.

13

What is found in the cranial floor and what do they allow the passage of?

A number of foramina (holes) are found within the cranial floor that allow passage for anatomical structures such as cranial nerves and blood vessels between extra- and intra-cranial compartments.

14

Although the bony skull is a tough and resilient structure and provides protection for the brain, severe trauma (such as impact injuries or blows) may result in fractures. Skull fractures can damage the underlying brain and/or blood vessels. What would bleeding within the cranial cavity cause?

An intracranial haematoma (epidural/extradural or subdural) which can compress the underlying brain tissue

15

If a px presented with a head injury what would be the first steps to take?

Examine the head and any wounds thoroughly and undertake a neurological assessment to determine whether there is evidence of or risk for brain injury.

16

If there is clinical suspicion of intracranial haemorrhage or brain injury secondary to trauma, what kind of imaging should be done?

CT imaging

17

Other than the brain, what other structure may be damaged in a significant head injury?

If there has been significant injury to the head consideration must also be given to the possibility of injury to the cervical spine.

18

If significant force is transmitted to the skull base through the vertebral column, fractures can occur through the cranial floor. What is the name given to these types of fractures?

Basilar skull fractures

19

What are the clinical signs to look for in the case of basilar skull fractures?

1) Presence of Battle’s sign (bruising over the mastoid process)
2) Raccoon eyes (bruising around both eyes)
3) haemotympanum (bleeding behind the eardrum)
4) CSF rhinorrhea (CSF leaking form the nose)
5) CSF otorrhoea (CSF leaking from the ears)

20

Which bones is the facial skeleton or viscerocranium formed by?

Formed by bones enclosing the orbits, nasal cavity, oral cavity, paranasal sinuses and includes the maxillae (the upper jaw) and the mandible (the lower jaw).

21

The frontal bone forms the skeleton fo the forehead and articulates with which bones?

Nasal bones
Zygomatic bones
Lacrimal
Sphenoid
Ethmoid

22

The frontal bone forms the _________ of the orbit and the __________ of the cranial cavity

Roof
Floor

23

What is the name given to the sharp bony ridge found above the orbital margin? What is significant about this region of bone?

Supraciliary arch

The skin overlying this area can be easily split when there is a blunt force injury to this area of the head.

24

Where do the zygomatic bones lie and what do they articulate with?

The zygomatic (cheek) bones, which lie on the inferolateral sides of the orbit articulate with the frontal, sphenoid, temporal bones and the maxillae.

25

Where are the maxillae found and how are thy different to the mandible?

The maxillae, which constitute the greater part of the upper facial skeleton, form the upper jaw (which is fixed to the cranial base).

Whereas, the mandible is moveable because it articulates with the cranial base at the temporomandibular joint (TMJ).

26

The most common facial fracture involve which bones?

- the nasal bones (due to the prominence of the nose)
- zygomatic bone
- and/or mandible

(Nose, cheek and jaw)

27

When there is a hard blow to the jaw, which aspects of the mandible may fracture and what may be associated with these fractures?

Fracture of the neck of the mandible and its body.

May be associated with TMJ dislocation.

28

Why are fractures to the bones of the mid face particularly concerning?

They cause a separation of some or all of the midface from the skull base, and can present problems for the patient’s airway

29

How are injuries to the midface classified depending on the plane fo the injury and the bones involved?

Le Fort classification

30

How many bones does the skull consist of?

22