The human ear has two sensory functions. One, to gather and focus sound waves to allow us to perceive sound (hearing). Two, to detect positional changes associated with movement (equilibrium). The ear performs both of these functions using mechanoreceptors: specialized cells that detect movement and transmit nerve impulses to the brain. This document will focus on the sense of hearing.

Sound waves are nothing more than mechanical vibrations moving through the air around us. Sound waves are focused by the fleshy outer part of the ear called the pinna. The pinna acts like a funnel, collecting sound waves traveling through the air and directing them into a narrow tube called the auditory canal. The auditory canal is a few centimeters long and ends in the tympanic membrane, or eardrum, which is a small, tightly stretched, drum-like membrane. The sound waves make the eardrum vibrate, just as a drum vibrates when you strike it.

The middle ear also consists of the auditory tube (or Eustachian tube), which leads from the middle ear to the pharynx. This canal is used to maintain air pressure on both sides of the eardrum

As the oval window vibrates, it sends vibrations into a snail-shaped structure called the cochlea. Within the cochlea, there is a fluid called perilymph. The vibrations create pressure waves in the fluid. In addition to perilymph, the cochlea is lined with tiny hair cells that are pushed back and forth by these pressure waves, much like sea grass being pushed back and forth by ocean waves.

The mechanical movement of these hair cells, which are mechanoreceptors, generate nerve impulses. These impulses travel down the vestibulocochlear nerve to the temporal lobe of the brain, where the auditory cortex interprets the electrical signals as sound.

In the next picture your can see the different parts of the hearing organ in a 3D guide.