Skull osteology-Cranial base

Question 1

cranial base is divided into how many regions

Answer 1

3

Question 2

what are the 3 cranial base regions

Answer 2

-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)

Question 3

the anterior cranial fossa is occupied by

Answer 3

inferior and anterior parts of the frontal lobes

Question 4

anterior cranial fossa is formed by what bones

Answer 4

-frontal bone (orbital parts)- anteriorly

-ethmoid bone -middle

-sphenoid bone (body and lesser wing)- posteriorly

Question 5

surface of anterior cranial fossa shows

Answer 5

brain markings of orbital gyri

Question 6

frontal bone of anterior cranial fossa forms

Answer 6

-frontal crest- median bony extension

-foramen caecum- base

Question 7

ethmoid bone of anterior cranial fossa forms

Answer 7

-crista galli- median ridge posterior to foramen caecum

-cribriform plate- sieve like passage for olfactory nerves to olfactory bulb

Question 8

ethmoid bone is what type of bone of the skull

Answer 8

deepest skull bone

Question 9

ethmoid bone contributes to what structures (what structures does it give off)

Answer 9

perpendicular plates

superior & middle nasal concha

cribriform plate

crista galli

Question 10

what happens in an anterior cranial fossa fracture

Answer 10

-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)

Question 11

what should happen if a sinus is involved in a fracture

Answer 11

antibiotics must be given prophylatically as the sinus renders it a compound fracture even if the skin is intact

Question 12

what are raccoon eyes

Answer 12

periorbital edema and bruising

Question 13

what kind of fracture do raccoon eyes suggest

Answer 13

frontal basal fracture

Question 14

middle cranial fossa is composed of

Answer 14

large depressions on each side

small depression called sella turcica

Question 15

the middle cranial fossa is formed by which 3 bony parts

Answer 15

greater wing of sphenoid bone

squamous part of temporal bone -laterally

petrous part of temporal bone- posteriorly

Question 16

middle cranial fossa is separated from anterior cranial fossa by

Answer 16

sphenoid crest laterally

sphenoid limbus medially

Question 17

middle cranial fossa is separated from posterior cranial fossa by

Answer 17

petrous crest of temporal bones laterally

dorsum sellae of sphenoid medially

Question 18

middle cranial fossa supports

Answer 18

temporal lobes of the cranium

Question 19

what surrounds the sella turcica

Answer 19

anterior and posterior clinoid processes

Question 20

the sella turcica is composed of what 3 parts

Answer 20

tuberculum sella anteriorly

hypophysial fossa (pituitary fossa)

dorsum sellae

Question 21

what over hangs the sella turcica in the middle cranial fossa

Answer 21

lesser wings of sphenoid

Question 22

the sphenoid bone can also be called

Answer 22

keystone bone because its in contact with all of the other cranial bones

Question 23

sphenoid bone is made up of

Answer 23

lesser wing

greater wing

sella turcica

optic canal

F. Rotundum

F. Ovale

F. Spinosum

F. Lacerum

superior orbital fissure

lateral & medial pterygoid P

Question 24

what is the sphenoid bone

Answer 24

a prominent, irregular, wedge shaped bone at the base of the skull

Question 25

what are landmarks of the sphenoid bone

Answer 25

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

Question 26

what are the 4 foramina that perforate the sphenoid bone

Answer 26

superior orbital fissure foramen rotundum foramen ovale foramen spinosum foramen lacerum

Question 27

the superior orbital fissure is between superior orbital fissure transmits what

Answer 27

lesser and greater wings opthalmic veins and nerves entering the orbit (CN III< CN IV, CN V, CN VI and sympathetic fibers)

Question 28

where is the foramen rotundum what does the foramen rotundum transmit

Answer 28

posterior to the medial end of the superior orbital fissure maxillary nerve ( CN V2)

Question 29

where is the foramen ovale located where does the foramen ovale open what does the foramen ovale transmit

Answer 29

posterolaterally to foramen rotundum infratemporal fossa mandibular nerve ( CN V3) and small accessory meningeal artery

Question 30

where is the foramen spinosum located what does the foramen spinosum transmit

Answer 30

posterolateral to foramen ovale middle meningeal vessels and meningeal branch of mandibular nerve

Question 31

what is the foramen lacerum what covers the foramen lacerum the foramen lacerum contains a groove for

Answer 31

artifact of dried skull cartilage the greater petrosal nerve posteriorly and laterally

Question 32

optic canal transmits what

Answer 32

CN II (optic nerve) ophthalmic artery

Question 33

fractures of the middle cranial fossa can result in

Answer 33

otorrhea

Question 34

whats otorrhea

Answer 34

leakage of blood and CSF from the ear

Question 35

otorrhea suggests

Answer 35

fracture of the temporal bone with torn meninges

Question 36

why is the base of the skull commonly involved in fractures

Answer 36

bcz its more fragile than the vault

Question 37

which part of the temporal bone is rarely involved in fractures

Answer 37

petrous part ( rock like)

Question 38

posterior cranial fossa is what compared to the others

Answer 38

largest and deepest

Question 39

posterior cranial fossa is formed by

Answer 39

occipital bone dorsum sella of sphenoid medially petrous and mastoid parts of the temporal bone anterolaterally

Question 40

whats the clivius

Answer 40

centrally inclined part of occipital bone

Question 41

what does the posterior cranial fossa contain

Answer 41

cerebellum pons medulla oblongata

Question 42

the posterior cranial fossa is divided by

Answer 42

the internal occipital crest into 2 crebellar fossae

Question 43

the internal occipital fossa ends up in the

Answer 43

internal occipital protuberance ( confluence of dural venous sinuses)

Question 44

what are in the grooves located anterolaterally of the posterior cranial fossa

Answer 44

transverse and sigmoid dural venous sinuses

Question 45

what foramina and apertures does the posterior cranial fossa have

Answer 45

foramen magnum jugular foramen hypoglossal canal internal acoustic meatus

Question 46

what does foramen magnum transmit

Answer 46

medulla and meninges vertebral arteries spinal roots of CN XI dural veins anterior and posterior spinal arteries

Question 47

what does the jugular foramen transmit

Answer 47

CNs IX, X, XI superior bulb of internal jugular vein inferior petrous and sigmoid sinuses meningeal branches of pharyngeal and occipital arteries

Question 48

what does the hypoglossal canal transmit

Answer 48

hypoglossal nerve ( CN XII)

Question 49

what does the internal acoustic meatus transmit

Answer 49

facial, vestibulocochlear nerves ( CN VIII)

Question 50

Describe the walls of the cranial cavity in (men and women) and (children and the elderly)

Answer 50

thinner in females than men thinner in children that the elderly

Question 51

bones of the walls of the cranial cavity contain

Answer 51

internal and external tables of compact bone

Question 52

tables of the cranial cavity are separated by

Answer 52

diploe

Question 53

what does the diploe contain

Answer 53

red bone marrow canals containing diploic veins

Question 54

the clivus is formed from what bones

Answer 54

sphenoid and occipital bones

Question 55

what can be seen in children and young adults and shouldnt be confused with a fracture

Answer 55

the spheno occipital synchrodrosis

Question 56

what accounts for majority of skull base growth

Answer 56

clivus

Question 57

what can happen in a posterior fossa fracture

Answer 57

blood may appear from under muscles near the mastoid process days afterwards