Skull Flashcards
What two groups is the skull divided into?
Neurocranium and viscerocranium
How many bones are in the neurocranium?
8
How many bones are in the viscerocranium?
12
What does the neurocranium do?
Encase the brain
What does the viscerocranium do?
Make up the facial skeleton and jaw
What are the 3 parts of the neurocranium?
Calvaria (skull cap)
Cranial floor
Cranial cavity
How does the skull cap ossify?
Begins as a membrane so inter-membranous ossification
How does the floor and base of the skull develop?
Begins as cartilage so endochondrial ossification
What does the viscerocranium surround?
Oral cavity, pharynx and upper respiratory passages
What does the viscerocranium develop from?
Pharyngeal arches
How many bones are there in the skull?
22
What is a fossae?
Shallow depression or hollow
What is a canal?
A bony tunnel
What is a foramina?
Round hole
What is a fissure?
Narrow slit hole
Why does the cranial floor need holes?
So cranial nerves and blood vessels can get to and from the brain
What are the three bowl shapes depressions in the cranial floor called?
Anterior, middle and posterior cranial fossae
What is the arrangement of calvaria bone and why?
Trilaminar
Protective strength without adding much weight
What are the three layers of the calvaria?
Outer table-hard bone
Diploeic cavity- spongy bone
Inner table
What are sutures?
Intersections between bones of the skull
Fibrous joints
Why are sutures serrated?
To prevent slippage and movement
When does suture lines stop growing?
Puberty
How are suture lines obliterated?
Gradually from inside to outside
What cannot pass through suture lines?
Cephalohaematoma
What do infant skulls have that adults do not?
Fontanelles
Large areas of unossified membranous gaps between bones
What do fontanelles allow?
Alteration of skull in child birth
Permits growth of the brain
When do anterior fontanelles fuse?
18months- 2 years
What can you tell from anterior fontanelles?
Healthy if convex
Can tell inter-cranial pressure and hydration from palpation
What is early fusion of fontanelles called?
Craniosyntosis
When do posterior fontanelles fuse?
1-3months
What is the biggest concern with a skull fracture?
Intercranial injury
If a intercranial injury is suspected what would you do?
CT scan
What is linear displacement of the skull?
No bone displacement
What is depressed displacement of the skull?
Fragment displaced towards brain
What is the issue with cranial base fractures?
Cranial nerve injuries
Cerebrospinal fluid leaks
What is the pterion and what is the issue with it?
Thinnest area of skull where suture lines meet
Middle meningeal artery lies beneath so can cause intercranial haemorrhage if fractures
What will basilar skull fractures cause?
Black eyes
Bruises behind the ear
Where are common sites of facial fractures?
Nasal
Zygomatic bone and arch
Mandible
