S2 osteology Flashcards
2 parts of skull
neurocranium (envelops/protects brain):
- calvaria (skull cap/vault)
- cranial floor
- cranial cavity
viscero cranium - facial skeleton and jaw:
neurocranium- how do these bones begin?
calvaria- as membranes (intramembranous ossification)
floor - as cartilage (endochondrial ossification)
flat bones of calvaria
frontal parietal greater wing of sphenoid bone temporal occipital
joints of calvaria
coronal suture- between frontal and parietal
bregma - where coronal suture and sagittal meet
saggital- between two paired parietal
lambdoid- between occipital and parietal
lambda- (previous fontanelle). meeting of saggital and lambdoid
what is fontanelle? function? fuse when?
infant skull
area of unossified membranous gaps between bones of calvaria
> allows for alteration of skull size and shape during birth
permit growth of brain
fuse
anterior - 2yrs
posterior - 1 to 3 months
what is craniosynostosis?
early fusion of fontanelles and sutures (rare condition) require survival intervention to break joint. and allow movement of skull bones
clinical relevance of anterior fontanelle?
convex shape- healthy baby
gentle palpation to assess intracranial pressure and state of hydration
- bulges under high pressure
- depresses when dehydrated
take in context with how baby appears
what is the arrangement of calvaria bones in cross section?
trilaminar arrangement
- compact bone= outer table
- spongy bone= diploe
- compact bone=inner table
> offers protective strength without adding significant weight
-periosteum covers outer and inner table
what depressions form the cranial floor?
anterior, middle and posterior cranial fossae (bowl shaped depressions)
where is ethmoid bone found?
anterior cranial floor
nose part
which bones form cranial floor?
- ethmoid bone
- sphenoid bone ( 2wings)
- temporal bone
- occipital bone
what bone houses middle and inner ear structures?
petrous (very hard bone) part of temporal bone
difference between linear and comminuted skull fractures?
linear- fairy straight, no bone displacement
comminuted-multiple fracture lines. fragments may displace inwards(depressed)
what is the thinnest area of skull? its underlying vessel?
pterion- meeting of 4 bones
underlying blood vessel= middle meningeal artery
what is a basilar fracture? signs and symptoms?
skull base fracture -rarer
SS:
fluid dripping from nose after hard injury (CSF)- ethmoid fracture
periorbital ecchymosis- bruising around eyes > fracture. of orbital plates of anterior cranial fossa
battle sign- bruising around mastoid process- involving petrous bone
blood and CSF leaking from ear- middle cranial fossa involving petrous bone
haemotympanum-blood pooling in middle ear cavity
bones of viscerocranium
facial skeleton:
- zygomatic x2 (cheek bone)
- maxilla (house upper teeth)
- nasal (bridge of nose)
- lacrimal (inner eye socket)
- mandible (jaw)
first line imaging of skull fracture?
CT scan
see internal structures
most readily fractured part of facial skeleton
zygoma- forms part of zygomatic arch
what is the temporomandibular joint? innervated by? stabilised by?
articulation between temporal bone and mandible
- synovial hinge joint
- divided into town synovial cavities by fibrocartilaginous disc
innervated by: auriculotemporal nerve
(branch of mandibular division of trigeminal nerve)
stabilised by
joint capsule
3 extra capsular ligaments
clinical conditions TMJ
TMJ disorder >clicking locking of jaw in open position due to anterior dislocation of condyle over there articular tubercle. contraction of muscles around joint keep it locked in anterior displacement
dislocation >secondary to trauma or excessive yawning
arthritis
what are the movements of TMJ?
hinge (rotational) action
by inferior joint capsule
gliding forward action
by superior joint capsule
> to depress mandible (open jaw)
muscles involved with elevation of mandible:
masseter
temporalis
medial pterygoid
muscles involved with depression of mandible
lateral pterygoid
gravity!
> condyle slides ONTO articular tubercle (not in front off…only In front when TMJ dislocated)
muscles involved with protrusion of mandible (sticking jaw out forward)
lateral pterygoid
medial pterygoid
