Session 2 - Skull Anatomy Flashcards
(36 cards)
What is the Neurocranium?
The part of the skill that protects the brain (8 bones)
- Calvaria (skull cap)
- Cranial Floor (base)
- Cranial Cavity
What is the Viscerocranium?
Facial Skeleton & Jaw
(14 bones)
Surrounds oral cavity, pharynx & upper respiratory tract.
How do neurocranial structures communicate with other head & neck structures?
‘Holes’ in the cranial floor, for the brain stem, nerves and vessels.
Which structures form the cranial floor?
Anterior, middle & posterior cranial fossae.
Describe the structure of the bones of the Calvaria (skull cap)
- Outer table (compact bone)
- Diploeic cavity (trabecular bone)
- Inner table (thinner layer of compact)
What is a Fontanelle?
The anatomical feature in infants.
The soft membranous gaps between the cranial bones.
What are suture lines? Name three important ones.
The intersections between the bones of the skull.
Saggital= between the two parietal.
Coronal= between the parietals and frontal.
Lambdoid= Between the parietals and the occipital.
Describe the structure of the suture lines through life.
Serrated and interlocked to prevent slippage.
Growth stops at puberty.
Gradually ossify from inside out.
How is the periosteum adhered to the outer table of bone?
Adheres closely to the bone, though continuous, it adheres STRONGLY to suture lines.
What is a cephalohaematoma? How is it diagnosed?
A sub-periosteal bleed.
Will be over only ONE bone, as periosteum is tightly adhered to suture lines.
What is a subgaleal haemorrhage?
Sub-aponeurotic bleed, between skull aponeurosis and periosteum.
Can spread over whole skull.
Patients can form raccoon eyes.
What is the purpose of the fontanelles?
Allow for alteration of skull size and shape in child birth, and allow growth in infant brain.
What is Craniosyntosis?
Early fusion of fontanelles and sutures (rare)
When do the fontanelles usually fuse?
Early infancy
Anterior= ~18 Months - 2 Years
Posterior= ~1-3 Months
How is the anterior fontanelle clinically relevant?
In examining newborns.
- Slightly convex shape.
- Inspection & gentle palpation can asses Intracranial pressure and state of hydration.
What is an important clinical test for any suspected skull injury or fracture?
Risk of intracranial injury!
CT scanning on ALL patients with know/suspected skull fracture.
Name and describe the two main types of skull fracture.
Linear:
Pass full thickness of skull, straight, no bone displacement.
Depressed:
Fragment is displaced inwards towards brain/
What are basilar skull fractures?
Fractures involving cranial base.
What are some common signs of basilar skull fractures?
-Cerebrospinal fluid leaks. (Ears/nose) -Racoon eyes -Bruising around mastoid process (Battle’s sign) - Cranial nerve injuries
Rare!
What is the Pterion?
The thinnest area of the skull, where the parietal, frontal, sphenoid and temporal bones join.
Why is a blow to the pterion particularly dangerous?
If fractured, the middle meningeal artery lies under this structure.
Can cause intracranial haemorrhage.
Describe the layers of the meninges.
Three layers surrounding the brain.
- Dura - thick tough outer
- Arachnoid - in between, transparent
- Pia - tightly adhered to the brain
What are the layers of the dura?
- Outer periosteal layer (endosteum lining inner skull bones)
- Meningeal layer - adjacent to arachnoid
Where do the dural layers separate?
Dural folds
Dural venous sinuses
