Osteology and Radiology of the Skull & The TMJ 1 - Terminology + Vault Of Neurocranium Flashcards
How many bones are in the skull?
22
What are the two groups of skull bones?
How many bones are in each group?
- neurocranium: 8 bones | encases brain
- viserocrnium: 14 bones | facial skeleton + jaw
What are these osteological features?
- fossae
- canal
- foramina
- fissures
- fossae: shallow depressions or hollows
- canal: bony tunnels
- foramina:round holes
- fissures: narrow slits
Describe the neurocranium
What are the 3 parts?
- made up of 8 bones
- encase + protect brain
3 parts:
- calvaria: skull cap/vault
- cranial floor: base
- cranial cavity
Describe the ossification of the parts of the neurocranium
- intramembranous ossification: vault bones begin as membranes
- endochondrial ossification: floor begins a cartilage
Describe the viserocranium
- made of 14 bones
- facial skeleton +jaw
- bones begin as membrane or cartilage >ossify
- structures develop from pharyngeal arches
What do vault bones of the neurocranium begin as?
Name this ossification
- membranes
- intramembranous ossification
What do floor bones of the neurocranium begin as?
Name this ossification
- cartilage
- endochondrial ossification
Name the bones of the calvaria
- frontal bone
- parietal bones
- greater wing of sphenoid bone
- temporal bone
- occipital bones
Name the sutures of the neurocanium
- coronal suture
- Sagittal suture
- lambdoid suture
What is the coronal suture between?
Frontal bone + paired parietal bones
What is the Sagittal suture between?
The two parietal bones
What is the lambdoid suture between?
Paired parietal bones + occipital bone
What is the bregma?
The intersection between the coronal + Sagittal suture
What is the lambda?
The intersection between the Sagittal + lambdoid suture
What are fontanelles in the infant skull?
Large areas of unossified membranous gaps between flat bones of calvaria
Functions of fontanelles
- allow for alteration of the skull size + shape during childbirth
- permit growth of infant brain
Where is the anterior fontanelles located?
When does it fuse?
- Area of the bregma
- 18months - 2 years
Where is the posterior fontanelles located?
When does it fuse?
- Area of lambdoid
- 1 - 3 months
What is craniosynostosis?
Early fusion of fontanelles + sutures
Clinical use of the anterior fontanelles
- slightly convex shape in healthy baby
- gentle palpation can be used to assess intracranial pressure + state of hydration
- high pressure > bulging
- dehydrated > sunken
What is a bulging anterior fontanelle a possible sign of?
High intracranial pressure
What is a sunken anterior fontanelle a possible sign of?
Dehydration
Describe the bones of the calvaria
What is their arrangement?
- mainly flat with a curved surface
- trilaminar arrangement:
- compact bone inner +outer table
- diploe (spongy bone) in middle
Describe the trilaminar arrangement of the bones in the calvaria
- compact bone (outer table)
- diploe (spongy bone)
- compact bone (inner table)
- protective strength without adding significant weight
What covers the surface of bones?
Periosteum
Where does the blood accumulate between when the middle meningeal artery ruptures causing an extra-dural haemorrhage?
Between the inner table of bone + periosteum
What features are different in the fetal skull compared with the adult skull?
In the fetal skull:
- fontalles
- absence of erupted teeth
- small nasal cavity, maxilla + mandible
- absence of mastoid + styloid process
- large calvaria relative to face
Feature of the sphenoid bone
Sella turcica
Pituitary gland sits within it
