Skull Flashcards by James Zechella

How many bones are there in the skull?

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What can the skull be divided into?

Neurocranium

Viscerocranium

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How many bones are there in the neurocranium?

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What are the bones that make up the neurocranium?

Frontal bone

Parietal bones x 2

Temporal bones x2

Occipital bone

Ethmoid bone

Sphenoid bone

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How many bones are there in the viscerocranium?

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What is the neurocranium?

The part of the skull that contains and protects the brain

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What are the parts of the neurocranium?

Calvaria

Cranial floor

Cranial cavity

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What is the calvaria?

The cap of the neurocranium

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What is the cranial floor?

The base of the neurocranium

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What is the cranial cavity?

The space in the neurocranium

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What type of ossification forms the bones of the calvaria?

Intramembranous ossification

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What type of ossification forms the bones of the cranial floor?

Endochondral ossification

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What is the basic structure of the cranial floor?

Has fossae
each fossa has foramina
some have fissures, canals etc.

Has grooves

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What is the purpose of the fossae of the cranial floor having foramina, fissures, canals etc.

Allows structures to pass between the neurocranium and the viscerocranium/neck

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What are the main structures passing through the foramina, fissures, canals etc. of the fossae of the cranial floor?

Cranial nerves

Blood vessels

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What do cranial nerves pass between?

Brain, brainstem
and
Face, neck

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What runs in the grooves of the cranial floor?

Dural venous sinuses

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What are the layers of the bones of the calvaria?

Periosteum

Outer table

Diploic cavity

Inner table

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What is the outer table of the calvaria bones made up of?

Compact bone

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What is the diploic cavity of the calvaria bones made up of?

Spongey bone

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What is the inner table of the calvaria bones made up of?

Compact bone

What is the advantage of the cross-sectional structure of the calvaria bones?

Protective strength

without significant weight

What do the layers of the bones of the calvaria look like on a CT scan?

Inner and outer tables appear white/light grey

Diploic cavity appears darker grey

What is the viscerocranium?

The part of the skull that makes up the face and the jaw

What does the viscerocranium contain and protect?

Oral cavity Pharynx Nasal cavity, paranasal sinuses

What is the name of the joints between the bones of the skull?

Sutures

What type of joint are sutures?

Fibrous joints

What shape are sutures?

Irregular lines

What is the advantage of sutures being shaped as irregular lines?

Prevents slippage and movement of bones along each other

What do sutures look like on a CT scan?

Look like fractures (but are not!)

When does bone growth at sutures occur?

Between birth and puberty

What happens to sutures after puberty?

They ossify from the endosteum to the periosteum

What does the periosetum do at sutures?

Tightly adhered to suture line Continues running through the suture, to become the endosteum covering the inner surface of the bone

What is the clinical significance of the periosteum tightly adhering to suture lines?

If there is haemorrhage beneath the periosteum it can only occur above that bone of the skull, cannot enter the skull because it cannot pass across the suture line

What is it called when a haemorrhage occurs beneath the periosteum?

Sub-periosteal haemorrhage

What are fontanelles?

Large areas of membrane | between the bones of the calvaria

What is the advantage of fontanelles?

Allow for alteration of skull size and shape assists with deliver through birth canal allows brain and associated structures to grow within it in infancy

What age group have fontanelles?

0-2 years

What are the two main fontanelles in infants?

Anterior fontanelle Posterior fontanelle

What is the shape of the anterior fontanelle normally?

Convex when palpating it

Where is the anterior fontanelle located?

Same place as adult bregma

How is the anterior fontanelle examined clinically?

Inspection and gentle palpation

What information can examination of the anterior fontanelle give?

Intracranial pressure State of hydration

What causes a bulging fontanelle?

Raised intracranial pressure

What causes a sunken fontanelle?

Dehydration

Where is the posterior fontanelle located?

Same place as adult lambda

When does the anterior fontabelle complete intramembranous ossification?

Approximately 1.5 years - 2 years

When does the posterior fontanalle complete intramembranous ossification?

Approximately 1-3 months

What is craniosyntosis?

Early ossification of fontanelles and sutures

What are the consequences of craniosyntosis?

Alters shape of skull Prevents growth of brain

What do the fossae of the cranial floor contain?

Each hold different parts of the brain and its associated structures

What are the differences between the adult and foetal skull?

Foetal skull has a larger neurocranium compared to its viscerocranium Foetal skull lacks erupted teeth, mastoid process and styloid process