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Head and Neck > Lec 4- Osteology and Radiographic Appearance of the Skull > Flashcards

Lec 4- Osteology and Radiographic Appearance of the Skull Flashcards

1
Q

What can the skull be split into?

A

The cranium and mandible.

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2
Q

What can the cranium be subdivided into?

A

The neurocranium - those bones forming a protective box around the brain.
The viscerocranium - those bones forming the facial skeleton.

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3
Q

What is the cranial cavity?

A

This is the space within the cranium, which holds the brain.

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4
Q

What does the neurocranium consist of?

A
  1. The Calvaria - skull or cranial cap or roof of the cranium, with no lower limit to it as such.
  2. The Cranial floor
  3. May also include the cranial cavity.
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5
Q

Describe the structure of the Calvaria and how it relates to function?

A
  • the bones of the calvaria consist of two layers of compact bone that are separated by a layer of spongy bone, called the dipole.
  • This tri-lamina arrangement of compact and spongy bone conveys protective strength to the skull without adding significant weight.
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6
Q

What can severe blows to the neurocranium result in?

A
  • may result in local depression and splintering of the bone or a series of linear fractures radiating away from the initial point of injury.
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7
Q

Why is the pterion an area of clinical importance?

A
  • A fracture at the pterion will injure the middle meningeal artery (its anterior branch) which lies immediately beneath the bone.
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8
Q

What is the pterion?

A

It is the thinnest part of the calvaria.

It lies on the lateral aspect of the skull.

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9
Q

What does bleeding from the anterior branch of the middle meningeal artery result in?

A

It causes 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.

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10
Q

What lies between the large flat bones that form the calvaria and function?

A

serrated, immobile joints known as sutures (coronal, sagittal and lambdoid)

  • The interlocking nature of these joints make it very difficult for the bones forming the joint to dislocate.
  • as we age these suture lines begin to ossify.
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11
Q

How is the cranial floor divided?

A

Into three areas/fossae:
anterior
middle
posterior

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12
Q

What are the bones forming the cranial floor?

A
  • frontal
  • ethmoid (in between the frontal)
  • sphenoid
  • temporal
  • parietal (round the circumference)
  • Occipital
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13
Q

What do the foramina (holes) in the cranial floor allow?

A

allows a passage for anatomical structures such as cranial nerves and blood vessels between extra- and intra- cranial compartments.

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14
Q

What is an important thing to do when a patient presents with a head injury?

A
  • It is important to examine the head and wounds thoroughly and undertake a neurological assessment to determine whether there is evidence of or risk for brain injury.
  • When there is clinical suspicion of intracranial haemorrhage or brain injury secondary to head trauma, CT imaging of the head will be necessary.
  • If there has been significant injury to the head consideration must also be given to the possibility of injury to the cervical spine.
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15
Q

What is a basilar skull fracture?

A
  • fracture through the cranial floor as a result of force being transmitted to the skull base through the vertebral column.
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16
Q

What indicates the presence of a basilar skull fracture?

A 
The presence of:
Battle's sign- bruising over the mastoid process
Raccoon eyes - bruising around both eyes
Haemotympanum - blood behind the eardrum
cerebrospinal fluid (CSF) 
-----leak from the nose (CSF rhinorrhea)
-----leak from the ear (CSF otorrheoa)
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17
Q

What is the facial skeleton/ viscerocranium formed of?

A

It is formed by bones enclosing the orbits, nasal cavity, oral cavity, paranasal sinuses and include the maxillae (upper jaw) and the mandible (the Lower jaw).

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18
Q

What are the main features of the anterior aspect of the skull?

A 
the frontal and zygomatic bones.
the orbits 
nasal region 
maxillae
mandible
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19
Q

What does the frontal bone do?

A
  • It forms the skeleton of the forehead
  • It articulates with the lacrimal, ethmoid and sphenoid bones.
  • It forms the roof of the orbit and part of the floor of the cranial cavity.
20
Q

What is the supraciliary arch?

A

It is a sharp bony ridge just above the orbital margin.
The skin overlying this area can be easily split when there is a blunt force injury to this area of the head.
-The skin over the eyebrow splits, the bone is not fractured.

21
Q

Where does the zygomatic (cheek) bones lie?

A

They lie on the inferolateral sides of the orbit, which articulate with the frontal, sphenoid, temporal bones and the maxillae.

22
Q

What do the maxillae do?

A

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

23
Q

Why is the mandible moveable?

A

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

24
Q

What are the most common facial fractures?

A
  • They involve the nasal bones ( due to the prominence of the nose), zygomatic bone and/ or mandible.
25
Q

What does a hard blow to the lower jaw often result in?

A

Results in a fracture of the neck of the mandible and its body.
It may also be associated with TMJ dislocation.

26
Q

What do fractures to the bones of the mid face result in?

A

They cause a separation of some or all of the mid face from the skull base and can present problems for the patients airway.

27
Q

What is the Le Fort classification (Type I,II, III)?

A

It is a way of classifying injuries to the mid face depending on the plane of the injury and bones involved.

28
Q

How many bones are there In the skull?

A

22

29
Q

What are some examples of osteological features that bones have?

A
  • shallow depressions or hollows called fossae.
  • Bony tunnels called canal.
  • Holes
  • —> roundish = foramina
  • —> Narrow slits = fissures
30
Q

How many bones are in the neurocranium?

A

8

31
Q

How many bones are in the viscerocranium?

A

14

32
Q

How do the calvaria and cranial floor bones begin?

A

Calvaria - begin as membranes by intramembranous ossification.

Cranial floor - begin as cartilage by endochondrial ossification.

33
Q

How do the viscerocranium bones begin?

A

They begin as membranes or cartilage and ossify.

34
Q

What are the bones of the Calvaria?

A
  1. frontal
  2. occipital
  3. Temporal
  4. Sphenoid
  5. parietal
35
Q

What are the joints in the Calvaria?

A
  • There are fibrous joints between the bones that join the bones and these are called sutures.
  1. Coronal suture - runs in the coronal plane.
  2. Sagittal suture - runs in the sagittal plane.
  3. Lambdoid suture – joins occipital bone to parietal.
36
Q

What is the point of intersection between the sagittal and coronal sutures called?

A

It is called Bregma.
It is the point of the anterior fontanelle in infants.
It still remains membranous in the infant skull.

37
Q

What is the point of intersection between the lambdoid and sagittal sutures called?

A

it is called Lambda

It is where the posterior fontanelle was in the infant skull.

38
Q

What are fontanelles?

A

-They are large areas of membrane/ unossified membranous gaps between flat bones of the calvaria.

39
Q

What do fontanelles do?

A
  • They allow for alteration of the skull size and shape during child birth.
  • they permit growth of the infant brain.
40
Q

When are fontanelles supposed to fuse?

A
  • They are supposed to fuse in early infancy.
    • anterior – 18 months to 2 years
  • -posterior –1 to 3 months.
41
Q

What happens if the fontanelles fuse early?

A

Can lead to Craniosyntosis

This will have implications on growth of the brain and shape of the head.

42
Q

What can you observe fro examining the anterior fontanelle in newborns?

A
  • Inspection and gentle palpation of the anterior fontanelle can be used to assess intracranial pressure and state of hydration.
43
Q

What is the periosteum?

A

The periosteum is an outer membrane that covers the surface of outer and inner table of skull bones.
-The periosteum is strongly adhered at suture line and continuous through suture and onto inner table of same bone.

44
Q

What does periosteum determine?

A

It determines the extent of haematoma in certain types of bleeds following head injury.

  • This is because bleeding may happen between the inner table of bone and periosteum.
  • – If bleeds, it strips the periosteum away from the bone and fills the space.
  • Since the periosteum is really strongly adhered , it limits how far can strip away.
45
Q

What are two types of cranial floor fractures?

A
  1. Linear –> These are fairly straight and involve no bone displacement.
  2. Comminuted (multiple fracture lines) –> The fragments may or may not displace inwards towards the brain (depressed vs non-depressed)

Head and Neck (8 decks)

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