Special Senses: Vision - Structures and Function
Anterior segment
Anterior and posterior chambers, all structures anterior to the lens Helps maintain the intraocular pressure of the eye and provides nutrients for the avascular lens and cornea
Choroid
a blood vessel rich dark membrane the blood vessels nourish the other layers of the eye, and the melanin helps to absorb excess light
photoreceptors
a sensory cell that responds to light. contain the photopigment rhodopsin in their mebrane
fovea centralis
a small area of the retina containing only cones, is the area of greatest visual activity when light is focused there
macula lutea
an area of high cone density, fovea centralis located in the middle
iris
anterior portion of the vascular layer that is pigmented, containing two layer of smooth muscle (sphincter pupillae and dilator pupillae) that control the amount of light entering the eye by changing the diameter of the pupil
optic disk
blind spot where the optic nerve leaves
Aqueous Humor
clear fluid between the lens and cornea maintains the pressure needed to inflate the eye, provides nutrition for the central cornea
cornea
continuous with the sclera; modified to form a transparent layer bulging anteriorly forms a clear window that is the major light bending medium (refracting) of the eye
optic nerve
each of the second pair of cranial nerves, transmitting impulses to the brain from the retina at the back of the eye. made of ganglionic cells and consist of over 1million nerve fibers
vitreous humor
gel like substance located in the posterior segment, provides the major internal reinforcement of the posterior part of the eyeball and helps to keep the retina pressed firmly against the wall of the eyeball
zonules
halo of fine fibers that extends from the ciliary process around the lens, attaching the two
retina
layer at the back of the eye containing phtoreceptors. receives light that the lens has focused, converting it to neural signals to be sent to the brain for visual recognition
posterior segment
located behind the lens, contains the vitreous humor. keeps the retina pressed firmly agains the wall of the eyeball
ciliary body
modification of the choroid that encircles the lens, contains the ciliary muscle and the ciliary process
rhodopsin
molecule stimulated when light hits the eye (found in rods), starts process of converting light into nervous signal into an action potential
sclera
opaque white connective tissue that forms the white of the eye, helps to maintain the shape of the eyeball and provides an attachment point for the extrinsic eye muscles
cones
photoreceptors responsible for the color vision, and are used for more clear vision
pupil
round central opening of the iris allows light to enter the eye
lens
separates the anterior and posterior compartment refracts the light into the fovea centralis when contracted correctly
pigmented epithelium
single layer of post mitotic cells functioning as a selevtice barrier to and a vegetatice regulator of the overlying phtoreceptor, playing a key role in its maitenance
ciliary muscle
smooth muscle within the ciliary body alters the shape of the lens with contraction and relaxation
rods
specialized photoreceptors for dim light, help detect black and white
optic chiasma
splits the vision to be interpreted on opposite sides of the brain