Skull osteology-Cranial base Flashcards
cranial base is divided into how many regions
3
what are the 3 cranial base regions
-anterior cranial fossa (house for frontal lobes)
-middle cranial fossa (house for temporal lobes)
-posterior cranial fossa (house for occipital lobes, cerebellum and medulla oblongata)
the anterior cranial fossa is occupied by
inferior and anterior parts of the frontal lobes
anterior cranial fossa is formed by what bones
-frontal bone (orbital parts)- anteriorly
-ethmoid bone -middle
-sphenoid bone (body and lesser wing)- posteriorly
surface of anterior cranial fossa shows
brain markings of orbital gyri
frontal bone of anterior cranial fossa forms
-frontal crest- median bony extension
-foramen caecum- base
ethmoid bone of anterior cranial fossa forms
-crista galli- median ridge posterior to foramen caecum
-cribriform plate- sieve like passage for olfactory nerves to olfactory bulb
ethmoid bone is what type of bone of the skull
deepest skull bone
ethmoid bone contributes to what structures (what structures does it give off)
perpendicular plates
superior & middle nasal concha
cribriform plate
crista galli
what happens in an anterior cranial fossa fracture
-the cribriform plate may be fractured
-results in tearing of the overlying meninges
-patient will have bleeding from the nose and leaking of CSF into the nose (rhinorrhea)
what should happen if a sinus is involved in a fracture
antibiotics must be given prophylatically as the sinus renders it a compound fracture even if the skin is intact
what are raccoon eyes
periorbital edema and bruising
what kind of fracture do raccoon eyes suggest
frontal basal fracture
middle cranial fossa is composed of
large depressions on each side
small depression called sella turcica
the middle cranial fossa is formed by which 3 bony parts
greater wing of sphenoid bone
squamous part of temporal bone -laterally
petrous part of temporal bone- posteriorly
middle cranial fossa is separated from anterior cranial fossa by
sphenoid crest laterally
sphenoid limbus medially
middle cranial fossa is separated from posterior cranial fossa by
petrous crest of temporal bones laterally
dorsum sellae of sphenoid medially
middle cranial fossa supports
temporal lobes of the cranium
what surrounds the sella turcica
anterior and posterior clinoid processes
the sella turcica is composed of what 3 parts
tuberculum sella anteriorly
hypophysial fossa (pituitary fossa)
dorsum sellae
what over hangs the sella turcica in the middle cranial fossa
lesser wings of sphenoid
the sphenoid bone can also be called
keystone bone because its in contact with all of the other cranial bones
sphenoid bone is made up of
lesser wing
greater wing
sella turcica
optic canal
F. Rotundum
F. Ovale
F. Spinosum
F. Lacerum
superior orbital fissure
lateral & medial pterygoid P
what is the sphenoid bone
a prominent, irregular, wedge shaped bone at the base of the skull
what are landmarks of the sphenoid bone
greater wings- which are large projections of bone that help to form the lateral border of the skull
lesser wings- are smaller lateral projections of bone above the greater wings
pterygoid processes- are 2 long downward projections from the greater wings that act as a point of muscle attachment
sella turcica- which is a turkish saddle which cradles the pituitary gland
what are the 4 foramina that perforate the sphenoid bone
superior orbital fissure
foramen rotundum
foramen ovale
foramen spinosum
foramen lacerum
the superior orbital fissure is between
superior orbital fissure transmits what
lesser and greater wings
opthalmic veins and nerves entering the orbit (CN III< CN IV, CN V, CN VI and sympathetic fibers)
where is the foramen rotundum
what does the foramen rotundum transmit
posterior to the medial end of the superior orbital fissure
maxillary nerve ( CN V2)
where is the foramen ovale located
where does the foramen ovale open
what does the foramen ovale transmit
posterolaterally to foramen rotundum
infratemporal fossa
mandibular nerve ( CN V3) and small accessory meningeal artery
where is the foramen spinosum located
what does the foramen spinosum transmit
posterolateral to foramen ovale
middle meningeal vessels and meningeal branch of mandibular nerve
what is the foramen lacerum
what covers the foramen lacerum
the foramen lacerum contains a groove for
artifact of dried skull
cartilage
the greater petrosal nerve posteriorly and laterally
optic canal transmits what
CN II (optic nerve)
ophthalmic artery
fractures of the middle cranial fossa can result in
otorrhea
whats otorrhea
leakage of blood and CSF from the ear
otorrhea suggests
fracture of the temporal bone with torn meninges
why is the base of the skull commonly involved in fractures
bcz its more fragile than the vault
which part of the temporal bone is rarely involved in fractures
petrous part ( rock like)
posterior cranial fossa is what compared to the others
largest and deepest
posterior cranial fossa is formed by
occipital bone
dorsum sella of sphenoid medially
petrous and mastoid parts of the temporal bone anterolaterally
whats the clivius
centrally inclined part of occipital bone
what does the posterior cranial fossa contain
cerebellum
pons
medulla oblongata
the posterior cranial fossa is divided by
the internal occipital crest into 2 crebellar fossae
the internal occipital fossa ends up in the
internal occipital protuberance ( confluence of dural venous sinuses)
what are in the grooves located anterolaterally of the posterior cranial fossa
transverse and sigmoid dural venous sinuses
what foramina and apertures does the posterior cranial fossa have
foramen magnum
jugular foramen
hypoglossal canal
internal acoustic meatus
what does foramen magnum transmit
medulla and meninges
vertebral arteries
spinal roots of CN XI
dural veins
anterior and posterior spinal arteries
what does the jugular foramen transmit
CNs IX, X, XI
superior bulb of internal jugular vein
inferior petrous and sigmoid sinuses
meningeal branches of pharyngeal and occipital arteries
what does the hypoglossal canal transmit
hypoglossal nerve ( CN XII)
what does the internal acoustic meatus transmit
facial, vestibulocochlear nerves ( CN VIII)
Describe the walls of the cranial cavity in (men and women) and (children and the elderly)
thinner in females than men
thinner in children that the elderly
bones of the walls of the cranial cavity contain
internal and external tables of compact bone
tables of the cranial cavity are separated by
diploe
what does the diploe contain
red bone marrow
canals containing diploic veins
the clivus is formed from what bones
sphenoid and occipital bones
what can be seen in children and young adults and shouldnt be confused with a fracture
the spheno occipital synchrodrosis
what accounts for majority of skull base growth
clivus
what can happen in a posterior fossa fracture
blood may appear from under muscles near the mastoid process days afterwards
