AP Bio eye structures and functions

Aqueous humor

(produced by ciliary body) Fills the anterior chamber and bathes the iris and lens; transmits light, maintains fluid pressure

Choroid

A blood vessel-rich layer of the middle eye that is darkened by the brownish pigment melanin to prevent light scattering

Ciliary muscle

A ring shaped muscle of the eye that encircles the lens and attaches to it by short fibers

Retina

Absorbs, transduces light energy

Optic nerve

Carries signals to brain

Iris

Circular muscle that adjusts the shape of the pupil to regulate how much light enters the eye

Cornea

Composed of transparent crystalline proteins

Sclera

Covers the rest of the eye's outer surface

Pupil

Entrance for light

Lens

Focuses light on the photoreceptors

Ciliary body

Holds the lens in place just behind the pupil

Conjunctiva

Protective mucous membrane that lines the inner surface of the eyelids and folds back to cover most of the eye's outer surface

Blind spot

Region of the retina through which the optic nerve exits the eye -- lacks photoreceptors so cannot respond to light

Vitreous body

Transmits light, supports lens and eyeball