3.1.1 Osteology of the Skull Flashcards
What are the two main parts of the skull?
Viscerocranium- face
Neurocranium-Brain
What bones make up the neck?
Cervical Vertebrae C1-C7
Atlas C1 (1 earth)
Axis C2 (2 axis x and y stfu about z)
What are some characteristics about cervical vertebrae? (look back at msk)
- Triangluar vertebral foramina
- Transverse foramina (konduit for vertebral artery, vein and sympathetic nerves)
- Bifid spinous process (not C7)
What are some characteristics about the Atlas?
C1
* No vertebral body
* No spinous process
* Lateral masses
* Odontoid Peg/ Dens articulates with anterior part
* Has grooves for C1 spinal nerve posteriorly
What are some characteristics about the Axis?
C2
* Odontoid peg (dens)
* Articulates with C1
* Forms the atlantoaxial joint
How many bones are in the skull?
22
What are some important osteological features of the skull?
- Shallow depressions or hollows (fossae)
- Bony tunnels (canal)
- Holes- round-ish=foramina and Narrow slits=fissures
What does the neurocranium consist of?
8 Bones- Encases/protects brain
Calvaria (skull cap/vault), cranial floor (base) and cranial cavity
How do vault bones begin?
Begin as membranes, ossifies via intramembranous ossification
How do floor/base bones begin?
Cartilage, ossifies via endochondrial ossification
How does the viscerocranium begin?
14 bones
* Bones begin as membrane or cartilage and ossify
* Structures (most) develop from pharyngeal arches (1&2)
Label the bones
Label the sutures
Bregma is where coronal and sagital suture meet
Lambdoid is where lambdoid and sagittal sutures meet
Why are sutures so irregular?
Serrated to prevent movement in newbornes, areas not fully ossified at this point
What are fontanelles?
Large areas of unossified membranous gaps between flat bones of calvaria
What do fontanelles do?
Allows alteration of skull size during child birth
Permits growth of infant brain
When do fontanelles fuse?
Anterior- 18-24 months
Posterior- 1-3 months
What is craniosynostosis?
Rare condition in which there is easly fusion of fontanelles and sutures
Brain is compressed and unable to grow, can lead to deformity and neurological problems if not treated
Need to break bone and allow it to re-fuse
What is the shape of the anterior fontanelle?
Slightly convex
How can the anterior fontanelle be used clinically?
Inspection and gentle palpation to assess intracranial pressure and hydration
Bulging=high ICP
Sunken=dehydrated
How is the cross-section of the calvaria arranged?
Trilaminar
Outer table- compact
Diploe- spongy bone
Inner table- compact
What does a trilaminar arrangement do?
Confers protective strength without adding significant weight
What covers each bone of the calvaria?
Periosteum- covers outer and inner table
Continuous through suture and onto outer table of bone
What does the periosteum cause in intracranial exdural haemorrhages?
Distinct lemon shape on CT of extradural haemorrhage
This occurs as periosteal dura is strong around suture lines and edges of bone, as bleeding occurs within periosteal dura is stripped from inner table but the periosteal dura is particularly strongly adhered at the sutures so it causes this distinctive shape as the blood cannot expand further
