Skull Flashcards
How many bones are there in the skull?
22
What can the skull be divided into?
Neurocranium
Viscerocranium
How many bones are there in the neurocranium?
8
What are the bones that make up the neurocranium?
Frontal bone
Parietal bones x 2
Temporal bones x2
Occipital bone
Ethmoid bone
Sphenoid bone
How many bones are there in the viscerocranium?
14
What is the neurocranium?
The part of the skull that contains and protects the brain
What are the parts of the neurocranium?
Calvaria
Cranial floor
Cranial cavity
What is the calvaria?
The cap of the neurocranium
What is the cranial floor?
The base of the neurocranium
What is the cranial cavity?
The space in the neurocranium
What type of ossification forms the bones of the calvaria?
Intramembranous ossification
What type of ossification forms the bones of the cranial floor?
Endochondral ossification
What is the basic structure of the cranial floor?
Has fossae
each fossa has foramina
some have fissures, canals etc.
Has grooves
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
What are the main structures passing through the foramina, fissures, canals etc. of the fossae of the cranial floor?
Cranial nerves
Blood vessels
What do cranial nerves pass between?
Brain, brainstem
and
Face, neck
What runs in the grooves of the cranial floor?
Dural venous sinuses
What are the layers of the bones of the calvaria?
Periosteum
Outer table
Diploic cavity
Inner table
What is the outer table of the calvaria bones made up of?
Compact bone
What is the diploic cavity of the calvaria bones made up of?
Spongey bone
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
