Osteology of the Skull Flashcards
Which structures can be seen on an open mouth x-ray?
C1 either side of dens
What does foramina mean?
Round-ish hole
What does fissure mean?
Narrow slit hole
What are the main large bones of the skull?
- Frontal bone – contain metopic suture, forehead, part of orbital cavity
- Temporal bone –
- Spenoid bone – great wing + lessor wing
- Parietal bones
- Zygomatic – with temporal bone forms zygomatic arch
- Occipital bone –
- Maxilla bones – 2 make up upper jaw,
- Mandible – jaw bone
What is a suture in the skull?
- Fibrous joint between bones in the skull
- Serrated
- Periosteum cover and lies between the sutures
- Eventually they completely ossify = from inside to out
What is the suture between the parietal bones?
Sagittal
What is the suture line between the parietal bones and the frontal bone?
Coronal
What is the suture line between the occipital bone and the parietal bones?
Lamdoid
What is the name for the point at which the sagittal and lambdoid suture meet?
lambda
What is the name for the point at which the coronal and sagittal sutures meet?
bregma
What 2 groups can the skull be divided into?
Neurocranium = 8 bones, protect brain, calvaria + cranial floor + cranial cavity
Viscerocranium = 14 bones, facial skeleton, jaw
What is the calvaria?
Vault, top of the skull
Begins as membranes (intramembranous ossification)
Discuss the cranial floor
Bottom of the skull bowl
Begins as cartilage (endochondrial ossification)
Needs to permit cranial N, brainstem and blood vessels = via foramina, fissures, canals
Where is the cranial cavity?
Inside the calvaria and the cranial floor
What are the 3 bowl-shaped depression that form the cranial floor?
Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
What do grooves on the inner surface of the skull carry?
Dural venal sinuses
What are the layers of the calvaria?
Outer table = compact bone
Diploeic cavity = spongy bone
Inner table = compact bone
What does the tri-laminar arrangement of the calvaria confer?
Protective strength without adding significant weight
What are the common injuries to the skull?
Fracture of zygomatic bone and arch
Fracture of the nasal bones
Mandible fracture
Risk of intracranial injury = CT should be performed
What are the types of skull fracture?
Linear = full thickness, straight, no bone displacement
Depressed = displacement inwards
Basilar = involves cranial base, cranial N injury, CSF leaks (nose, ear), racoon eyes, battle’s sign
What is the thinnest part of the skull and therefore the easiest part to fracture?
Pterion = region where frontal, parietal, temporal, sphenoid join together
Can tear middle meningeal artery
Blows to the side of the head
What is blood behind the eardrum called and indicative of?
Hemotympanum
Fracture the petrous bone = basilar skull fracture
Differences in foetal and adult skull
Large areas of unossified membranous gaps = fontanelles
Anterior fuse = 18m – 2 years
Posterior fuse = 1-3m
What do we call early fusion of the fontanelles and sutures?
craniosyntosis
Outline a jeffersons fraction
Fracture of anterior and posterior arches of atlas
Axial load
May damage arteries at the base of the skull
Outline a hangmans fracture
Hyperextension of head on neck
Axis fracture through par interarticularis
Forward displacement of C1 and body of C2 on C3
Outline an odontoid peg fracture
Hyperextension/flexion
Visualise via open mouth AP x-ray
What is a cephalohaematoma?
Sub-periosteal
Bleeding between the periosteum and the bone
Cant pass suture line = cant pass intra-cranially
What is a subgaleal haemorrhage?
Bleed between aponeurosis and periosteum
Sub-Aponeurotic
Not limited by suture lines
Key features of the C spine
Bifid spinous process except C7
Foramen transversarium
Atlas – no vertebral body, no spinous process
Axis – dens, large spinous process
C1-C7
What can be seen on a CT head (bone window)?
Inner table and outer table – grey outlines
Diploic cavity = dark area between inner/outer table
Suture lines
