4. Osteology and Radiology of the Skull Flashcards
What is the neurocranium?
The bones that support or protect the brain
What is the viscerocranium?
Bones forming the facial skeleton
How many bones make up the skull?
22 (8 cranial, 14 facial)
What are the 2 parts of the neurocranium and by what method do they ossify?
Calvaria (skull cap) by intramembranous, Cranial floor (base) by endochondral
What are the bones of the calvaria?
Frontal, 2 parietal, 2 temporal, occipital, 2 greater wing of sphenoid
What are he different sutures of the calvaria?
Coronal (between frontal and parietal), Sagittal (between parietal), Lambdoid (between parietal and occipital)
What is the bregma and lambda?
Bregma (Coronal and sagittal sutures meet), Lambda (sagittal and lambdoid sutures meet)
What are fontanelles?
Areas of unossified membrane gaps between bones of calvaria (where the future bregma and labda are)
What is the function of fontanelles?
Allow alteration of the skull size and shape during childbirth. Permit infant brain growth.
At what age do the fontanelles fuse?
Anterior (18 months - 2 years), Posterior (1 - 3 months)
when do sutures fuse?
sutures not completely ossified in children and only ossify in adulthood
What is craniosynostosis?
Early fusion of fontanelles and sutures
What is the clinical significance of the anterior fontanelle when examining newborns and infants?
Inspection and gentle palpation can be used to assess intracranial pressure and state of hydration.
Bulging = raised intracranial pressure, Sunken = dehydrated
What is the trilaminar arrangement of the calvaria bones?
External and internal compact bone and spongy bone in the middle.
What are the compact bone of the calvaria referred to as?
Outer compact bone = outer table and inner compact bone = inner table
what is the advantage of the trilaminar arrangement?
confers protective strength without adding significant weight
What are all the bones of the calvaria covered in?
Periosteum covers surface of outer and inner table of skull bones
Strongly adhered to bone edges at suture line and continuous through suture and onto inner table of same bone
What is the clinical significance of the periosteum?
extradural Haemorrhage - rupture of MMA between periosteum and inner bone cause periosteum to be pulled off the bone. Blood will pool in this pocket. Periosteum at the sutures cannot be pulled away so blood is restricted to the area. - lentiform shape
What are the 3 parts of the cranial floor?
Anterior, middle and posterior cranial fossae
Which bones make up the anterior cranial fossa?
Frontal bone, ethmoid bone, and anterior parts of the body of and the lesser wings of the sphenoid bone
Which bones make up the middle cranial fossa?
the body and greater wing of the sphenoid, and the squamous and petrous parts of the temporal bone.
What is the zygomatic arch?
Cheekbone. Articulation of the zygomatic process of the temporal bone and temporal process of the zygomatic bone.
Which bones make up the posterior cranial fossa?
mastoid part of the temporal bone and the squamous, condylar and basilar parts of the occipital bone.
what does the petrous part of temporal bone house?
middle and inner ear structures
What surface landmarks are present on the external occipital bone?
external occipital protuberance, supreme, superior and inferior nuchal line
What are the 2 types of cranial vault fractures?
Linear (no bone displacement) or comminuted (multiple fracture lines)
What are the 2 types of comminuted fractures?
Depressed (fragements displaced inwards), non- depressed
What vessels has an important relationship with the pterion and what can fracture here cause?
Middle meningeal artery, extra dural haemorrhage
what is the thinnest area of skull?
pterion - really easy to fracture