Skull Flashcards
sutures
-several separate bones united at immobile joints
sutural ligament
-the connective tissue between bones in a suture
mandible
connected to the skull via the mobile temporomandibular joint
how are the bones of the skull divided?
into those of the cranium and those of the face
upper and lower part of the cranium
upper: the vault
lower: the base of the skull
composition of the bones of the skull
- made up of external and internal tables of compact bone separated by a layer of spongy bone(diploe)
- bones are covered on the outer and inner surfaces by periosteum
Diploe
a layer of spongy bone that separates the internal and external tables in the skull
internal table
-thinner and more brittle than the external table
Pterion
- junction of greater wing of sphenoid, squamous temporal, frontal, and parietal bones
- overlies course of anterior division of middle meningeal artery
- weak and exposed, so when youre hit there you can tear artery and die
Lambda
-point on calvaria at junction of lambdoid and sagittal sutures
Bregma
-point on calvaria at junction of coronal and sagittal sutures
vertex
- top most point of the skull
- superior point of neurocranium
- in middle with cranium oriented in anatomical plane
asterion
-star shaped
-located at junction of three sutures
parietomastoid
occipitomastoid
lambdoid
glabella
- smooth prominence (most marked in males)
- on frontal bones, superior to root of nose
- most anterior projecting part of the forehead
inion
-most prominent point of external occipital protuberance
nasion
-point on cranium where frontonasal and internasal sutures meet
parietal foramen
veins run through it to get to the sinus
Anterior cranial fossa
- foramen cecum
- cribriform foramina in cribiform plate
- anterior and posterior ethmoidal foramina
Foramen cecum
nasal emissary vein
cribriform foramina in cribriform plate
axons of olfactory cells in olfactory epithelium that form olfactory nerves
anterior and posterior ethmoidal foramina
vessels and nerves with the same names
Middle cranial fossa
- optic canals
- superior orbital fissure
- foramen rotundum
- foramen ovale
- foramen spinosum
- foramen lacerum
- groove/hiatus of greater petrosal nerve
optic canal
optic nerve(CN 2) and ophthalmic arteries
superior orbital fissure
ophthalmic veins, ophthalmic nerve , CN 3,4,6, sympathetic fibers
foramen rotundum
maxillary nerve
Foramen ovale
maxillary nerve and accessory meningeal artery
Foramen spinosum
middle meningeal artery and vein and meningeal branch of trigeminal nerve
Foramen lacerum
-deep petrosal nerve and some meningeal arterial branches and small veins
Groove/hiatus of greater petrosal nerve
-greater petrosal nerve and petrosal branch of middle meningeal artery
Posterior cranial fossa
- foramen magnum
- jugular foramen
- hypoglossal canal
- condylar canal
- mastoid foramen
foramen magnum
- medulla and meninges
- vertebral arteries
- CN 11
- dural veins
- anterior and posterior spinal arteries
Jugular foramen
- CN 4,5,6
- superior bulb of internal jugular vein
- inferior petrosal and sigmoid sinuses
- meningeal branches of ascending pharyngeal and occipital arteries
Hypoglossal canal
-hypoglossal nerve (CN 12)
condylar canal
-emissary vein that passes from sigmoid sinus to vertebral veins in neck
mastoid foramen
-mastoid emissary vein from sigmoid sinus and meningeal branch of occipital artery
the type of fracture depends on what?
- age of the patient
- severity of the blow
- area of the skull receiving the trauma
severe, localized blow
-local indentation, often accompanied by splintering of the bone
blows to the vault
- result in a series of linear fractures
- radiate out through the thin areas of the bone
petrous parts of the temporal bones and occipital crests
- strongly reinforce the base of the skull
- tend to deflect linear fractures
pond fracture
- common for children
- localized blow produces this, a depression without splintering
fractures of the anterior cranial fossa
- cribriform plate my be damaged
- results in tearing of the overlying meninges
- bleeding and leakage of CSF from the nose
- when orbital plate is fractured, result is hemorrhage into the orbital cavity and exophthalmos
- frontal sinus may be involved if hemorrhage into the nose
Fractures of the middle cranial fossa
- common because this is the weakest part of the skull
- leakage of blood and CSF from external auditory meatus
- may involve CN 7 and 8
- if cavernous sinus is torn, CN 3,4,6 may be damaged
Why is the middle cranial fossa so weak?
- numerous foramina and canals in this region
- cavities of middle ear and sphenoidal sinus
Fractures of the posterior cranial fossa
- blood may escape into the nape of the neck into the postvertrbral muscles
- days later, it can appear in posterior triangle, near mastoid process
- mucous membrane of nasopharynx can be torn and blood can escape
If jugular foramen is damaged, what CN are damaged?
CN 9,10,11
Why is hypoglossal nerve usually spared when there is a fracture of the posterior cranial fossa?
-hypoglossal canal walls are strong
why is there little displacement of bone fragments in facial fractures?
-the muscles of the face are thin and weak
fractured mandible exception
-the strong muscles of mastication can cause considerable misplacement of the fractured bone
most common facial fractures involve…
- nasal bones
- zygomatic bone
- mandible
maxillofacial fractures
- occur from massive trauma
- swelling of the face, bone moves, malocclusion of teeth, leakage of CSF due to cribriform plate fracture
- orbital wall damage=diplopia
- damage to infraorbital nerve=numb cheek and gum
- epistaxis
Le fort labeling
- sites of maxillofacial fractures
- Type 1: across maxilba, under nose
- Type 2: up, across nose, and down
- Type 3: across orbital region
