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