Ear

An ear is an organ used by an animal to detect sound waves. The term may refer to the entire system responsible for collection and early processing of sound (the beginning of the auditory system), or merely the externally-visible part. Not all animals have ears in the same part of the body.

The mammalian ear
Mammals, including humans, have two ears, one on each side of the head.


 * The outer ear is the external portion of the ear and includes the eardrum.


 * The middle ear includes the ossicles (three tiny bones), two muscle tendons (of the stapedius and tensor tympani muscles), and two nerve bundles (the horizontal portion of the facial nerve and a branch of the facial nerve called the chorda tympani).


 * The inner ear comprises both the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule.

Non-mammalian hearing organs
Spiders have hairs on their legs which are used for detecting sound.

Reptilian ears only have one bone — the columella (stapes) (see below).


 * Vestibular neuronitis