The outer part of the ear.

disease of the eardrum

the white layer that covers the outside of

the eye.

A nerve ending that reacts to

a change, such as heat or cold, in the body by sending a message to

the central nervous system

The opening within the iris through which light passes before reaching the lens and being focused onto the retina.

Pertaining to  the back surface

The colored tissue at the front of the eye that contains the pupil in the center.

An electrical signal that travels along a nerve fiber in response to a stimulus.

The organ of sight/vision in humans and animals.

The organ of hearing and balance in humans and other vertebrates.