Exam 2: Senses - Vision Flashcards
how often do you make vitreous humor
once in your entire life - diff from aqueous humor
where do you see remnants of vitreous humor development
hyaloid canal - now t no longer has any blood vessels going through it
- used to have a purpose of nourishing the lens
conjunctiva
protects and lubricates the eye by producing mucous and tears
palpebrae
muscle that raises upper eyelid and maintains that position
lacrimal glands
secrete water and electrolytes
have enzymes and antibodies (IgA) - protect from foreign things like contacts
keeps eye moist, clears dust and debris
drains into the nasal pharynz
path of light coming into the eye
- first comes in and hits cornea - transparent part of sclera - iit starts to focus and refract light
- through the anterior chamber to the lens - majority of focusing
- thrugh posterior chamber rays are converging on fovea centralis
from corner of eye - catch more movement than detailed pictures
if up close object - what does the lens do
balls up
if far away object what does the lens do
more curved - tighten ciliary suspensory ligaments and flatten it
fovea centralis
100% cones
gives most precise clear colorful vision
away from fovea centralis you inc % of rods till the edge of your vision
100% rods
only place where retina does not cover
optic disc - blind spot
blood vessels enter and leave
optic nerve forms here
problems with the eyes and high pressure
- you are constantly making aqueous humor
- it comes from the base near where sclera and iris meet and it puts nutrient fluid over the lens goes through and comes out the scleral venous sinus - canals of schlem)
drains out through trabeculae network which can get blocked
not draining of fluid —–inc P —–glaucoma
Pressure in anterior chamber pushes posterior chamber and viitreous humor spreads P to back of eye
- if too high it can crush the receptos
cataracts
cells of lens are living
- as you feed them with aqueous humor (has sugar level since from blood)
- if diabetic and sugar level already out of control
- make excess of sorbitol in sides of lens dehydrating it causing inc P
- high sugar level on outside working to dehydrate it
- damage cells
- get opaque lens, not clear , vision looks yellowed will not see things clearly
- use laser to destroy this, suck it out and put artificial lens in
astigmatism
lens and cornea
ex: looking at spokes to see if all same shade - if not ther may be astigmatisms
pupil diameter control - what inc and dec opening
inc opening: sphincter (circular muscle fibers)
dec opening: dilator (radial fibers)
unaccommodated position
ciliary muscle relaxed
increases tension on suspensory fibers
stretch/flatten lens
distance focus
accomodation
ciliary muscle contracts
decreases tension
allows lens to become rounder
near focus
presbyopia
lose elasticity
even releasing tension does not allow rounding - lens cannot do the curvature it needs
have to move what you are looking at farther away in order to focus
parasympathetic response what fibers contract
circular fibers
sympathetic response what fibers contract
radial fibers
emmetropic
normal sized eye
myopic
near sighted eyes
length of pathway in eye is too long so yyou have rays converging on imaginary point in front of the retina - disperse before get to retina - have to correct and push the focal point back
hypermetropic
far sighted
pathway is too short, converge past the fovea centralis
pigmented epithelium
helps absorb excess light - so you do not get a glare - has no role in vision
