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.