the skull - sphenoid and ethmoid Flashcards

1
Q

how many bones in the neurocranium

A

8 bones + 6 ear ossicles

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2
Q

how many ear ossicles are there

A

6

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3
Q

name bones of the neurocranium

A

frontal parietal occipital temporal ear ossicles sphenoid ethmoid

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4
Q

sphenoid bone

A

unpaired, complicated anatomy (butterfly shape)
occupies the middle of the skull
joins neurocranial and facial components of bones
peeks out in almost every aspect of the cranium
has a clear right and left side

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5
Q

how many ossification centers does the sphenoid bone have

A

14, but is a single bone at birth

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6
Q

what kind of ossification does the sphenoid bone undergo

A

endochondral (body, lesser wings) and intramembranous (pteryoid process), both in greater wings

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7
Q

three main parts of the sphenoid

A

body, greater and lesser wings, pterygoid plates

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8
Q

sphenoid body

A

air filled sinus inside and houses pituitary gland
located on midline
articulates with occipital @ basilar suture
forms nasal cavity wall anteriorly and articulates with ethmoid and vomer

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9
Q

sphenoid greater and lesser wings

A

lateral projections from body

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10
Q

pterygoid plates

A

inferior projections for attachment of muscles of mastication

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11
Q

sphenoidal sinuses

A

in sphenoid body
hollow cavities
communicate anteriorly with the nasal canal

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12
Q

greater wings

A

lateral projections
form most of middle cranial fossa
between maxilla and zygomatic

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13
Q

lesser wings

A

smaller and medial to greater wings

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14
Q

optic canals

A

carries optic nerve (visual signal from retina to brain) and ophthalmic artery (blood supply to eyes and nose)

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15
Q

sella turcica/turkish saddle

A

saddle shaped depression, located posterior and inferior to optic canals
sits on top of sphenoid body on midline

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16
Q

hypophyseal (pituitary) fossa

A

deepest depression of sella turcica
houses pituitary gland, important for growth

17
Q

anterior clinoid processes

A

posterior projections of the lesser wings
attachment site of tentorium cerebelli, segment of dura mater (meninges)

18
Q

superior orbital fissure

A

crescent shaped gap between greater and lesser wings
transmits cranial nerves
forms crescent of foramina

19
Q

crescent foramina

A

superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosa (anterior to posterior)

20
Q

foramen rotundum

A

perfect circle foramen under superior orbital fissure
inferior to superior orbital fissure at junction of greater wings and body
maxillary nerve

21
Q

foramen ovale

A

posterior to foramen rotundum
oval shaped
mandibular nerve
seen best from basilar view (base of skull)

22
Q

foramen spinosum

A

located posterolateral to foramen ovale on greater wings
middle meningeal vessels and branches from mandibular nerve

23
Q

orbital surfaces

A

anterior portion of greater wings
contribute to lateral walls of eye orbits

24
Q

pterygoid processes

A

inferior projections from body of sphenoid
divided into two thin plates (medial and lateral)

25
Q

medial pterygoid plate

A

articulates with palatine bone
has pterygoid hamulus

26
Q

pterygoid hamulus

A

hook like process at inferior tip
articulates with tensor veli palatini

27
Q

lateral pterygoid plate

A

parallel and lateral to medial pterygoid plate
thin vertical inferior projection

28
Q

medial surface of lateral pterygoid plate

A

attachment site for medial pterygoid muscle
elevates mandible (closes mouth)

29
Q

lateral surface of lateral pterygoid plate

A

attachment site for lateral pterygoid muscle
depresses mandible (opens mouth)

30
Q

ethmoid bone

A

unpaired bone of the upper nose, between the orbits along midline
light and spongy (delicate)
approximately the size of an ice cube
undergoes endochondral ossification

31
Q

where is the ethmoid bone visible

A

medial side of eye orbits
through ethmoid notch of the frontal bone (anterior cranial fossa)

32
Q

cribriform plate

A

located along the midline
covers superior aspect of ethmoid (between eye orbits)
perforated by many tiny foramina
olfactory nerve

33
Q

crista galli/rooster crest

A

perpendicular projection of the cribriform plate
between olfacturly bulbs in anterior cranial fossa
continuation of frontal crest attachment

34
Q

ethmoidal labyrinth (sinus)

A

lies on either side of the midline
contains numerous thin walled air cells
lateral walls (lamina orbitalis) form part of medial orbital walls

35
Q

perpendicular plate

A

flat bony lamina (plate) located along midline
inferior to crista galli and between the labyrinths
forms part of nasal septum