Lecture 4- Osteology and radiology of the brain Flashcards
how many bones does the skull consist of
22
shallow depression or hollows
fossae
bony tunnels
canals
round holes
foramina
narrow slit hole
fissues
Bones of the skull can be divided into two groups
1) Neurocranium (8 bones)
2) Viscerocranium (14 bones)
Neurocranium (8 bones): x
encases/ protects the brain
- Calvaria “skull cap or ‘vault’”, cranial floor (base) and cranial cavity
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bone formation in the calvaria “skull cap or ‘vauly”
intramembranous ossification
bone formation of the cranial floor (base)
endochondrial ossification- starts as cartilage
Viscerocranium (14 bones):
facial skeleton and jaw
- bones begin as membrane or cartilage and ossify
- structures develop from pharyngeal arches (1&2)
structure of the bones of calvariia
trilaminar arrangement
- Compact (outer table)
- Diploe (spongy bone)
- Compact (inner table)
Periosteum covers outer and inner table of skull bones- shrink-wrapped.
Strongly adhere to bone edges at suture line and continuous through suture and outer inner table of same bone
- Holes in cranial flood permit
- cranial nerves and blood vessels to enter into and out of neurocranium
- Foramina, fissures and canals
bones of the calvaria
- Frontal bone
- Parietal bones
- Greater wing of the sphenoid bone
- Temporal bone
- Occipital bones
joints of the calvaria
- coronal suture
- bregma
- sagittal suture
- lamboida suture
- lamda
coronal suture
joint qat the front of the skull running horizontally
bregma
where the coronal suture and saggital suture meet at the front
saggital suture
joint that runs straaight down the skull
lamboid suture
equivalent to the coronal suture but at the posterior part of the skull
lamda
joint where the lamboidal suture meets the sagittal suture
joints of the skull in infants
fontanelles
fontanelles
Late areas of unossified membranous gaps between flat bones of calvaria
- Allow for changing skull size and shape during childbirth
- Permit infant brain growth
- fontanelles Fuse in …..
- Anterior –
- Posterior-
- Fuse in early infancy
- Anterior – 18 months- 2 years
- Posterior- 1-3 months
craniosynotosis
- Rare condition= craniosynostosis (early fusion of fontanelles and sutures)
why is the anterior fontanelle useful clinically
Clinically useful when examining new-borns and infants
- Slightly convex shape in a healthy baby
- Inspection and gentle palpation of anterior fontanelle can be used to assess intracranial pressure and state of hydration
the cranial floor is formed by
- Three bowl shaped depressions form the cranial floor
- Anterior
- Middle
- Posterior crania fossae
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which bones for the cranial floor
- occipital bone- posterior
- temporal
- sphenoid
- ethmoid
- frontal
occipital bone forming the posterior cranial floor
frontal bone forming the anterior cranial floor
ethmoid bone forming the anterior cranial floor
sphenoid bone forming the middle cranial floor
temporal bone forming the middle cranial floor
……. part of temporal bone houses middle and inner ear structures
petrous
where is the thinnest part of the brain
pterion
pterion
where the different parts of the skull meet
- Important relationship between pterion and underlying blood vessel: middle meningeal (which is between the periosteum and the bone) (Anterior branch)
- Blows to the side of the head can fracture bone in area of pterion and injury blood vessel lying immediately below- intracranial (extra-dural)
