Eyeball
Globe, one-inch sphere with only about one-sixth of its surface visible
Extraocular
Outside the eyeball
Walls of the eyelid
Sclera, choroid, retina
Scelera
White of the eye, maintains the shape of the eye and protects the delicate inner layers of tissue
Tough, fibrous tissue forms the outer layer of the eye, except for the cornea
Choroid
Choroid coat, opaque middle layer of the eyeball that contains many blood vessels and provides the blood supply for the entire eye
Retina
Sensitive innermost layer that lines the posterior segment of the eye, receives nerve impulses and transmits them to the brain via the optic nerve