S2- Osteological and Radiographic Appearance of the Skull Flashcards

1
Q

what are foramina?

A

holes in the skull

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2
Q

what are fissures ?

A

narrows slit

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3
Q

how many bones are in the skull ?

A

22

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4
Q

How are the bones of the skull divided into two groups ?

A

Neurocranium and Viscerocranium

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5
Q

How many bones are in the Neurocranium ?

A

8 bones

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6
Q

Describe Neurocranium

A

Provides strength but lightweight and divided into A, M , P cranial fosse
Calavaria : skullcap - superior portions of frontal , occipital and L AND R parietal bones
Cranial base : provide articulation points for atlas and facial bones - made up of ethmoid, sphenoid , occipital ,L and R temporal and frontal bones

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7
Q

How do skull cap bones ossify and how do base bones ossify ?

A

skull cap - begin as membranes (intramembranous ossification)
Floor/base - as cartilage ( endochondrial ossification )

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8
Q

How many bones are in the Viscerocranium ?

A

14 bones , nasal, lacrimal, maxilla, zygomatic, inferior nasal conchae, mandible, vomer and palatine

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9
Q

How do structures develop in the skull ?

A

pharyngeal arches

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10
Q

What is the pterion and its clinical significance?

A

thinnest part of the skull , thin meeting part of frontal, parietal, temporal and sphenoid bones. Anterior branch of the middle meningeal artery is immediately beneath so fracture of this bone can cause an extradural heamorrhage

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11
Q

What is the arrangement in cross section of the bones of the skull cap ?

A

trilamina arrangement
outer table - compact hard bone
diploid cavity - spongy bone
inner table - compact hard bone

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12
Q

what are sutures ?

A

fibrous joints between bone, prevails prevent spillage , ossify in approx 20 years , potential weak points

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13
Q

name some examples of some sutures

A

coronal - frontal fusions with parietal
sagittal - fusion of both parietals
lambdoid - fusion of occipital of both parietals
squamous - separates squamous part of temporal from parietal
bregma - fusion of frontal and parietal ( anterior fontanelle)
lambda - fusion of parietal and occipital ( posterior fontanelle )

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14
Q

what is fontanelle and what is its clinical significance

A

large areas of unossified membranous gaps between flat bones of calvaria - allow for alteration of skull size and shape in infants
Anterior fuses - fuses 18 months - 2 years
posterior - 1 - 3 months

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15
Q

what its the early fusion of fontanelles and sutures known as ?

A

Craniosynostosis

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16
Q

what is the pooling of blood between the periosteum and the bone known as ?

A

cephalohaematoma
does not pass suture lines so cannot leave the skull
most commonly occurs in parietal bones

17
Q

how are intracranial injuries identified

A

ct scanning

18
Q

what the two main fracture types ?

A

linear - pass full thickness of skull and involve no bone displacement
depressed - fragment is displaced inwards towards the brain causing skull indentation and potential Brian injury

19
Q

what are fractures involving the cranial base ?

A

basilar skull fractures - associated with cranial nerve injuries
prone to causing cerebrospinal fluid leaks

20
Q

what are the clinical signs that indicate their presence of basilar skull fractures ?

A

battles signs - bruising over the mastoid process

raccoon eyes - ( periorbital ecchymosis) - bruising around both eyes

21
Q

what is the infra - temporal fossa ?

A

large space inferior and medial to zygomatic arch, medial and lateral pterygoid muscles are here

22
Q

what is the pterygopalatine fossa ?

A

very small space on the inferior surface of the skull between sphenoid and maxilla

23
Q

what is the middle cranial fossa ?

A

has pituitary gland, made up of sphenoid and temporal bones

24
Q

what is the posterior cranial fossa ?

A

deepest, made up of occipital and temporal bones, has brainstem

25
Q

what is the anterior cranial fossa ?

A

most shallow , over nasal and orbital cavities, accommodates anterioinferior portions of the frontal lobes of the brain

26
Q

what is meninges ?

A

three membranous layers that surround and protect the brain

27
Q

what are the three layers of meninges ?

A

Dura - tough outermost fibrous membrane
Arachnoid - soft translucent membrane
Pia- microscopically thin, delicate closely adherent to surface of brain

28
Q

how many layers do dura consist of ?

A

2
Periosteal - endosteum lining inner bones of skull
meningeal - layer adjacent to arachnoid

29
Q

what are dural folds and dural venous sinuses ?

A

separation of two layers forms dural folds and dural venous sinuses( venous blood filled spaces created by seperation of meningeal from periosteal layer of dura )

30
Q

what are some examples of dural folds ?

A

Falx Cerebri

Tentorium Cerebelli

31
Q

what are the attachment of the dural folds ?

A

FC - crista gali

TC- sits above cerebellum

32
Q

what is the function and clinical significance of dural folds ?

A

help to stabilise the brain and act as a rigid divider
a rise in pressure inside the skull can lead to compression and displacement of brain against rigid dural folds or through foramen magnum causing herniation

33
Q

what is the function of dural venous sinuses ?

A

major dural venous sinuses lie at the margins of borders of falx cerebri and on cranial floor. Venous blood from brain drains into the sinuses and eventually DVS drain into IJV

34
Q

how do cerebral veins within subarachnoid space drain into the DVS ?

A

bridging veins connect between the subarachnoid space into the dural venous sinuses

35
Q

what does the carvenous sinus drain into ?

A

drain into sigmoid sinus which goes through the jugular foramen, the skull becoming the IJV

36
Q

what does the carvenous sinus drain into ?

A

drain into sigmoid sinus which goes through the jugular foramen, the skull becoming the IJV

37
Q

what is a intracranial haemorrhage ?

A

head trauma can lead to bleeding in spaces between meningeal layers and blood vessels run along between the meningeal layers. Injury and bleeding from these blood vessels will cause accumulation of blood in the space between the meningeal layers

38
Q

what are the three types of intracranial haemorrhage ?

A

Extradural ( arterial blood, pear shaped on CT,MMA)
Subdural ( venous blood from a bridging vein, banana shaped on CT, falx cerebri prevents it going to other part of the skull)
Subarachnoid ( caused by trauma or spontaneous rupture of vessel - circle of willis, blood leaks into the subarachnoid space and mixes with CSF

39
Q

what is a intracerebral haemorrhage ?

A

blood can also occur within the brain tissue itself
addition of volume such as a bleed, to an already fixed space( the skull )leads to a rise in pressure and damage to brain tissue, brainstem and other important structures e.g cranial nerves