4 Osteology and Radiographic Appearance of the Skull Flashcards
The neurocranium is made up of 8 bones and its function if to encase and protect the brain. Name the 3 major components of the neurocranium?
- Calvaria (‘skull cap’ or ‘vault’)
- Cranial floor (base)
- Cranial cavity
How do the bones of the neurocranium develop?
(Hint: vault bones vs floor/base bones)
Vault bones: intramembranous ossification (begin as membranes)
Floor/base bone: endochodrial ossification (begin as cartilage)
The viscerocranium is made up of 14 bones. What do the majority of these bones develop from?
Pharyngeal arches
(more detail–> session 5)
Label the coloured bones in the following image:
Label the bones on this diagram:
Which bone is highlighted in this image?
Occipital bone
Name the suture on this image:
(like crown)
Fill in the missing labels in the following image:
Where on this image did the fontanelles used to be?
At bregma and lambda
What are fontanelles? What is their purpose (2)?
Large areas- unossified membranous gaps between flat bones on calvaria
Purpose:
- Allow movement to enable birth
- Allow development of brain
When do the anterior and posterior fontanelles fuse?
Anterior: 18-24 months
Posterior: 1-3 months
What is craniosynostosis?
Early fusion of fontanelles and sutures
Why might the anterior fontanelle be useful when examining newborns and infants?
(taken in context of how infant appears)
Fontanelle= slightly convex in shape (healthy)
Can be used to asses:
- Intracranial pressure
- State of hydration
Describe the trilaminar arrangement of the bone of the Calvaria (in cross section). Why is this important?
- Outer table (compact bone)
- Diploe (spongy bone)
- Inner table (compact bone)
Importance:
Protective strength without adding significant weight
Look at the following image showing a bleed from the middle menigeal artery. Why has the bleed not spread any further?
Middle meningeal artery runs between periosteum and inner table
(Periosteum ‘shrink wrapped’ every invidual bone of skull)
Blood strips away periosteum from inner table
…but at sutures= too strongly adhered- periosteum doesn’t pull away
Name the 3 ‘bowl shaped’ depressions that form the cranial floor:
Anterior, middle and posterior cranial fossae
What is the name of the bone highlighted in green:
Ethmoid bone
Name the bone that forms most of the floor of the anterior cranial fossa:
Frontal bone (+ethmoid bone)
Frontal bone also forms roof of orbits
What is the name of the bone highlighted in green?
Sphenoid bone
Label the parts of the temporal bone:
What structures can be found within the petrous part of the temporal bone?
Middle and inner ear structures
Label the parts of the occipital bone:
Skull fractures of the cranial vault can be linear or comminuted. What’s the difference between these 2?
- Linear= fairly straight, no bone displacement
- Comminuted= multiple fracture lines
- Can be depressed or non-depressed
What is the pterion?
Region where the frontal, parietal, temporal, and sphenoid bones join together
Why is the Pterion clinically significant?
- Thinnest area of skull- easy to fracture
- Underlying blood vessel: middle meningeal (anterior branch)
A patient presents with bilateral bruising of the eyes and a basilar skull fracture is suspected. Where is this fracture likely to be?
Anterior cranial fossa
A patient presents with blood coming out of their ear and a Hemotympanum (see image). A basilar skull fracture is suspected. Where is this fracture likely to be?
Petrous part of temporal bone
(Batter’s sign also suggestive of fracture of petrous bone)
Fill in the missing labels:
Out of the facial bones shown in this image, which ones are most likely to get fractured?
- Nasal
- Zygomatic (and zygomatic arch- see image)
- Mandible
Where is the fracture in this following x-ray? What has fractured?
If a fracture of the mandible is found on an x-ray, what should you always look for?
A second fracture- usually fractures in 2 places
Describe the temporomandibular joint.
Articulation between temporal bone and mandible
Synovial hinge-type joint (divided into 2 synovial cavities by fibrocartilaginous disc)
(Dislocation can be caused by yawning)
Describe the movement of the TMJ.
Depression of mandible:
- Hinge- rotational- action
- Gliding forward action
What happens if the condyle slips in front of the articular tubercle? How can this occur?
Dislocation of TMJ
Due to:
- Facial trauma
- Yawning
Jaw locked in open position
How does an adult skull differ from a fetal skull?
What is a jefferson fracture (aka burst fracture)? What is the likely mechanism of injury?
How can you obtain an AP x-ray of C1 and C2 (usually obscured by mandible).
How might the fontanelles be used to assess the wellbeing of a new born?
