Anatomy of the Ear

2012-09-04 The human ear consists of three parts:
The outer ear: consists of the auricle and the ear canal. Sounds are collected and guided through the ear canal to the middle ear. The sound arrives at the eardrum — a flexible, circular membrane — which starts to vibrate when sound waves strike it. The ear canal is more formally called the external auditory meatus (canal). On average, it is about 9 mm high by 6.5mm wide, and is roughly 2.5cm to 3.5cm long. The ear canal is nor quite a straight tube, but has two curves forming a slightly S-like pathway.

The middle ear: is an air-filled space separated from the outer ear by the eardrum tympanic membrane (pronounced: tim-'pa-nik). The sound waves are passed on by the movement of the eardrum to the middle ear. In the middle ear are three tiny bones: the malleus, incus and stapes, often referred to as the hammer, the anvil and the stirrup. They are collectively known as the ossicular chain. These form a bridge from the eardrum to another membrane at the entrance to the inner ear. Their interaction increases and amplifies the sound vibrations further before these are relayed fully into the inner ear via the oval window.

The inner ear: referred to as the cochlea (pronounced: kohk-le-a), is similar in shape to a snail shell. It contains several membranous sections which are filled with watery fluids. When the sound waves vibrate the oval window, the fluid begins to move, thus setting minute hair cells in motion. These hair cells then transform the vibrations into electrical impulses, which are sent via the auditory nerve and on to the brain. What we call "noises" are actually just "sound waves", which are transmitted through the air.