EYEBALL Flashcards
what is the outer layer of the eyeball wall called
fibrous tunic
what is the function of the sclera
white if the eye, protects and gives shape
what is the function of the cornea
refract rays of light and focus them onto the retina
what is the middle later of the eye called
vascular tunic
what us the function and structure of the choroid
dark brown membrane lining sclera. nourishes retina and absorbs light rays
what is the structure and function of the ciliary body
extends from retina to base of iris. alters shape of lens for focusing. also secretes aqueous humour
what is the function of the iris
alters size of pupil
what is the structure and function of the pupil
controls the amount of light entering the eye
what are the two muscles that are involved in constructing the pupil
circular and radial
what is the inner layer of the eye
retina
what is the function of the retina
lines posterior side of eyeball, involved in image formation and stores vitamin A
what are the two layers of the retina
nervous layer and pigmented layer
what are the three parts of the retina
macula lutea, fovea and optic disc
what is the macula lutea
small area in the centre of the retina
what is the fovea
in centre of macula, highest concentration of cones (photoreceptors)
what is the optic disc
where ganglion neurons bend posteriorly to form optic nerve, (blind spot)
what is the lens
flexible connective tissue, focuses light rays on the retina, attatched to sphincter muscles and divides the eye into posterior and anterior cavities
what is the conjunctiva
thin mucous membrane lines eyelids and covers front surface of eyeball
what is the function of conjunctiva
keeps eyeball moist
what is the function of eyebrows and eyelashes
prevent debris and perspiration from entering the eye
what does the aqueous humour do
maintains pressure on the eyeball, supplies lens and cornea with nutrients
where is the anterior cavity
between the cornea and lens
where is the posterior cavity
between the lens and the retina
what is the posterior cavity
filled wot vitreous humour and prevents eyeball from collapsing, holds the retina against the choroid
what are the two types of photoreceptors
rods and cones
what are rods
dim light and peripheral vision receptors but don’t provide sharp images
what are cones
provides high clarity and colour vision
what is the pigment in rods
rhodopsin. very sensitive to low intensities of light
where is light absorbed by photopigments
in the dendrites of the rods and cones
what causes colour blindness
absense or deficiency of one of the 3 types of cones (red, green or blue)
how is the lens involved in refraction of light rays
can curve the lens to get more refraction of light
