Structure of the Human Eye

retina

one of the coats to the eye, being an expansion of the optic nerve over the bottom of the eye, where the sense of vision is first received It is in the back of the eye and contains about 3 milliion cones and one billion rods.

fovea

the central region of the retina where images are focused.

choroid coat

a layer of blood vessels located between the sclera and the retina

pupil

a little aperture in the middle of the iris and uvea of the eye through which the rays of light pass to the crystalline humor to be painted on the retina

optic nerve

a nerve that transmits visual signals from the eye directly to the brain

lens

clear, flexible, convex shaped body that refracts the light projected on the retina, located between the cornea and the vitreous body (the major focusing structure)

suspensory ligament

flexible fibers that hold the lens in its place

cones

located in the retina, they detect color There are about 3 million in each eye

rods

located in the retina, they detect light and dark. There are about one billion in each eye.

iris

the colored circle surrounding the pupil of the eye; a smooth muscle that enlarges and diminishes the pupil It is located between the cornea and the lens and controls the amount of light entering the eye.

aqueous humor

the fluid produced in the eye and filling the spaces (anterior chamber and posterior chamber) in front of the lens and its attachments. It diffuses out of the eye into the blood and is regarded as the lymph of the eye, although its composition is different from that of the lymph in the rest of the body.

vitreous humor

the gel-like liquid that fills the cavity behind the lens to help maintain the shape of the eyeball

cornea

the transparent membrane in the forepart of the eye through which the rays of light pass.

uvea

the vascular tunic of the eye, comprising the iris, choroid coat, and ciliary body

sclera

the white part of the eye that holds the eye muscle in place; in front of the eye, it extends from the cornea, and in the back, the optic nerve penetrates the sclera

ciliary body

tissue that joins the iris to the choroid and produces aqueous humor The ciliary body is a part of the eye that includes the ciliary muscle, which controls the shape of the lens, and the ciliary epithelium, which produces the aqueous humor. The ciliary body is part of the uvea, the layer of tissue that delivers oxygen and nutrients to the eye tissues.