Oct18 M3-Anatomy_Orbit and Nose_Notes Flashcards
(dnm) intraocular mm fct
constrict or dilate pupil + change shape of lens
orbit charact
- cone shaped
- triangle in the back
- wall in between 2 orbits
other cavities in face
- paranasal sinuses (at least 4 of them, 2 on each side. 1 medial sup to orbit and 1 lat inf to orbit). are little pockets). open in the nasal cavities
- 2 nasal cavities
coronal cut of orbit charact
- cavity on top = cranial cavity
- midline plate = cribriform plate where olfactory n. sits
- orbital fissure in the back
- optic canal = small hole medial to orbital fissure where optic n passes
charact of bone around orbit
- diff thicknesses all around
- floor = thin layer of bone (bc pocket of empty bone (air circulating) underneath it, called the maxillary sinus). easily breakable bone, thin
- roof = thicker bc of thick frontal bone. so thick you have small cavities developing above orbit, called frontal sinuses
lobotomy done how
remove part of frontal lobe for behavioral tx by going through orbit, breaking roof and reaching frontal lobe of brain
orbit content
- lot of fat (70%)
- eyeball
- optic n. connecting to eyeball in the back
- extraocular muscles (levator palpebrae superioris m. for upper eyelid elevation + 6 mm for moving eyeball)
extraocular muscles moving the eyeball
- sup rectus = elevate
- inf rectus = depress
- lat rectus = abduct eyeball (move lat)
- medial rectus = adduct
- inf oblique (start on medial wall and insert lat inf, coming from underneath medially)
- sup oblique (start on medial wall and insert lat sup)
fct of inf oblique m.
- when looking straight, rotate eyeball laterally (counterclockwise) if the head tilts to maintain the visual field. called EVERSION (lat rotation)
- when eye adducted, elevate it by doing the eversion (so can look medial up)
fct of sup oblique
- like inf oblique when looking straight, but turning clockwise. called INVERSION (medial rotation). stroke involving this m = pat comes in with head tilted
- when eye adducted, depress it by doing the inversion
sup oblique m. trajectory
- comes from medial wall of orbit
- passes in trochlea (piece of bone, cartilage)
- one muscle belly before trochlea and one after
- 2nd ones does the inversion
- insert on lat side off eyeball
- supplied by trochlear n.
how to test fct of eye muscles
H test. move fingers in a H shape in front of pt eyes. each direction = specific mm involved
orientations of muscles and their origin in the orbit (what explains special fcts of sup oblique and inf oblique mm)
- the orbit is not perfectly AP and rather goes posterior = medial to anterior = lateral
- the eyeball axis however is perfectly AP
- bc of this diff, the muscles don’t come from back of eyeball but from medial wall of orbit
look up lat = what muscles
- lat rectus
- sup rectus
look down lat = what muscles
- lat rectus
- inf rectus
look up medial = what mm
- medial rectus
- inf oblique (because sup rectus is not aligned with AP axis of eyeball anymore but inf oblique now is)
look down medial = what mm
- medial rectus
- sup oblique (same reason. inf rectus not aligned with AP axis of eyeball anymore but sup oblique now is bc of its 7 shape bc of trochlea)