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)
CNs moving the eyeball
III, IV and VI
IV (trochlear n) to what m
superior oblique
-short trochlear n. medially directly diving in sup oblique
VI (abducens) to what m
lateral rectus (abducens n. is the name bc lateral rectus abducts the eye) -small n. on surface of lat rectus
III to what m
all others
- medial rectus
- inf rectus
- sup rectus
- inf oblique
- between sup rectus (inf) and levator papebrae superioris (sup) in middle of orbit*
branches of V1 relating to the orbit
note: V1 and V2 are mainly sensory. V3 is motor
- lacrimal nerve (branch of V1) = lat wall, over lat rectus, to lacrimal gland (so near abducens n.)(sensation of gland fct + SS and PSS inn to control it)
- frontal nerve (branch of V1) = midline of orbit, sup to all mm. splits in ant part of orbit
- supraorbital n. (branch) of frontal nerve (V1 branch) more laterally: for surface of eyeball + skin of forehead
- supratrochlear n. (branch) of frontal n. (V1 branch) more medial: inn. space between two eyebrows
summary of nn in orbit
medial to lat
- trochlear n. (CN IV) to sup oblique
- supratrochlear n. (branch of frontal n., branch of V1)
- frontal n.
- supraorbital n. (branch of frontal n., branch of V1)
- oculomotor n. (CN III) to 4 other extraocular mm
- abducens n. to lat rectus
- lacrimal n. (branch of V1) to lacrimal gland
how to determine what the problem is if notice that one eye is deviated when pt looks straight
deviated eye is bc of unopposed action of a muscle. so problem in the opposite muscle
one eye looking straight + other deviated medially dx
abducent nerve palsy
-disabled lateral rectus (unopposed adduction)
one eye looking straight + other deviated medially up dx
trochlear n. palsy
-disabled sup oblique m. (unopposed inf oblique eversion)
one eye looking straight + other deviated lat down dx
complete oculomotor palsy
- sup rectus, inf rectus, medial rectus and inf oblique disabled
- unopposed lat rectus and sup oblique
lacrimal apparatus
- lacrimal gland superolat (for lubrication over all conjunctiva = epith of eyeball) in the eye. produces tears then drained in system of ducts
- canaliculi for sup and inf eyelides (medially in orbit)
- lacrimal sac (medially between orbit and nose) travels in bone to the nose (nasal cavity)
- drains in nose
- no valves in the lacrimal apparatus*
problem related to no valves in lacrimal apparatus
fluid can go back up, high infection risk
anterior and nasal apertures def
- opening of nostrils in the front (can collapse)
- opening of nasal cavity in the back (nasal CHOANAE) into the nasopharynx (can not collapse bc formed by bone)
why useful that nasopharynx connects to mouth and nasal cavity?
can put mirror in back of mouth and look at nasal cavity from the back, check for obstruction, infection
name of chin bone
maxilla (top of upper teeth medially, the palate of the mouth)
-palate separates nasal cavity from oral cavity
gap in maxilla where air can circulate
- maxillary sinus
- bacteria can accum in these sinuses when we breathe
- the ethmoid bone and the inferior nasal concha are 2 plates of BONE covering the nasal cavity from the maxillary sinus
diff between the 3 nasal concha
- sup and middle nasal concha are plates coming off the ethmoid bone
- the inferior nasal concha is a separate bone by itself
- ALL 3 COVER OPENING of nasal cavity into maxillary sinus*
concha physiology
- create little air spaces for air circulation so also called nasal turbinates (bc turbulence to create warm ir from contact with blood vessels and epith on concha)
- epith of nasal cavity (covering concha) can get inflamed = stuffed nose, takes too much space, hard time to breathe bc nasal cavity is small (packed with bony processes and epith)
2 fcts of nasal conchae
- separate nasal cavity and maxillary sinus
- warm and humidify inhaled air
paranasal sinuses other than maxillary sinus (below eyes, lat to bottom nose)
- frontal sinuses (pockets in frontal bone at roof of orbit medially)
- ethmoid cells (little cavities inside ethmoid bone). medial to eyes, lat to top nose
- sphenoidal sinus (big cavity under cav sinus)
- ALL COMM WITH NASAL CAVITY*
- all these cavities grow with age so infection becomes more likely*
nasal septum and palatine bones def
- nasal septum = midline sep of 2 nasal cavities
- palatine bones = bone of palate. maxillary sinus above it. dentists are first to see maxillary sinus infection
where is the opening of sphenoidal sinus into nasal cavity
sup to superior concha
what openings are underneath the middle concha
- frontal sinus opening
- maxillary sinus opening
- ethmoidal bullae (openings of ethmoidal cells, small holes)
- so most openings underneath the middle concha*
what is the semilunar hiatus
little groove underneath the middle concha (so relates to maxillary sinus, frontal sinus and ethmoidal bullae) where frontal sinus opens into maxillary sinus
how surgery for pit tumor is done using the paranasal sinuses
- pit gland sits sup to sphenoidal sinus
- can access this sinus from the nose
- break posterior wall of sphenoidal sinus to access pituitary
clinical relevance of paranasal sinuses
infections
CT image with opacity in maxillary sinus, no prob of nasolacrimal duct, nasal cavity not obstructed, no fracture or bone damage: dx
infection of maxillary sinus
