Osteology of Skull, Hyoid & Cervical Spine Flashcards
how are bones of the skull joined
by fibrous joints called sutures
where is movement in the cranial skull
only at the temporomandibular joint and the atlanto-occipital joint
2 types of bones forming the skull
- flat & irregular bones
- pneumatised bones
flat & irregular bones
formed by intramembranous ossification & endochondral ossification respectively
pneumatised bones
bones with air cells / sinuses to reduce weight in the skull & add resonance to the voice
examples of pneumatised bones
frontal, temporal, sphenoid and ethmoid bones
2 divisions of the skull
- neurocranium
- viscerocranium (facial skeleton)
neurocranium bones (8)
frontal
2x parietal
occipital
sphenoid
2x temporal
ethmoid
viscerocranium bones (14)
2x palatine
2x lacrimal
2x nasal
2x zygomatic
vomer
2x inferior nasal concha
2x maxilla
mandible
main features of viscerocranium
zygomatic arch, mandible & infratemporal fossa
zygomatic arch
formed via the temporal process of the zygomatic bone and the zygomatic process of the temporal bone
infratemporal fossa
found deep to zygomatic arch, communicates to he temporal fossa superiorly, contains muscular & neurovascular structures
main features of neurocranium
external acoustic meatus, styloid & mastoid processes, temporal fossa
borders of the temporal fossa
superior border - superior temporal line
posterior border - inferior temporal line
anterior border - frontal process of zygomatic bone & zygomatic process of frontal bone
inferior border - infratemporal crest, deep to zygomatic arch
floor - pterion
vertex
most superior point of the neurocranium
bregma
junction of the coronal and sagittal sutures
lambda
where the lambdoid and sagittal sutures join
inion
most prominent point of the external occipital protuberance
asterion
a star shaped junction of 3 sutures between the occipital, parietal and temporal bones
pterion
H shaped junction of sutures (frontal, parietal, temporal and greater wing of sphenoid) that overlies the anterior branch of the middle meningeal artery
anterior fontanelle
diamond shaped, at site of bregma, fuses at around 18 months
posterior fontanelle
triangular in shape, at site of future lambda, fuses before the first year
what is the piriform arperture
this is the anterior nasal opening in the cranium
what passes through supraorbital foramen
CN V1 the ophthalmic branch of trigeminal nerve
what passes through the infraorbital foramen
CN V2 the maxillary branch of the trigeminal
where does CN V2 exit interiorly in the skull
foramen rotundum
what passes through the mental foramen
CN V3 the mandibular division of the trigeminal nerve
how does CN V3 exit the cranium
through the foramen spinosum
function of the vomer
contributes to the bony part of the nasal septum which separates the anterior nasal apertures & posterior nasal apertures (choanae)
what canals are in the temporal bone
- carotid canal for internal carotid artery
- jugular foramen for internal jugular vein (just posterior to the carotid canal)
what opening is present in the occipital bone
foramen magnum for spinal cord, meninges, vertebral & spinal arteries, spinal root of accessory nerve CN XI
what travels through the foramen spinosum other than CNV3
middle meningeal artery & vein
purpose of ligamentum nuchae
to attach external occipital protuberance & foramen magnum to spinal processes of the cervical vertebrae (continuous with supraspinous ligament)
function of ligamentum nuchae
to support head & resist flexion as well as an attachment point for some muscles
what is present in cervical vertebrae only compared to other vertebrae
presence of foramina transversaria
how does articulation occur in the cervical vertebrae
via articular facets with the superior facet articulating with the inferior facet of the preceding vertebrae
site of attachment of ligamentum nuchae
spinous process
when is the spinous process bifid / not bifid
bifid C2-C6
non bifid C7
other names of C1 and C2
C1 = atlas
C2 = axis
main feature of C2
dens / odontoid process
function of odontoid process
acts as an axis for the atlas and atlanto-occipital joint
what does C1 have instead of a body
an anterior arch with an articular facet for the dens of C2
what is missing at the atlanto-axial joint
between C1 and C2 there is no intervertebral disc
function of atlanto-occipital joint
allows flexion & extension (nodding)
function of lateral atlanto-axial joint
allows rotation of head from side to side
where is the hyoid bone found
C3 level in anterior neck
why is the hyoid bone unique
does not articulate with any skeletal elements in heck & neck and can be palpated
what keeps the hyoid bone in place
muscles and ligaments with connections to mandible, styloid process, thyroid cartilage, manubrium & scapulae
purpose of hyoid bone
connects oral cavity with the pharynx posteriorly, the larynx inferiorly and helps to keep the airway open
lesser horn of hyoid purpose
forms site of attachment for stylohyoid ligament which connects the hyoid to the styloid process of the skull
