Your ears detect sounds, so allowing you to hear. Sound waves are created by a vibrating source, such as a plucked guitar string. These sound waves are channelled into the ear and transmitted to its innermost part, the cochlea. Here sound vibrations are turned into nerve signals and sent to the brain where the sounds are actually "heard" and interpreted. The ears also send information to the brain that helps you balance.

The flap on the side of the head that we call the ear, is simply its outermost part. Called the pinna, this flap of skin and cartilage funnels channels sound waves in the outer ear canal. At the end of this canal, sound waves hit the eardrum, a taut piece of skin, and make it vibrate. These vibrations are transmitted and amplified by three tiny bones linked together: the hammer (malleus), anvil (incus) and stirrup (stapes). These are known as the ossicles. In-and-out movements of the stirrup transmits the vibrations into the fluid-filled inner ear where the snail-shaped cochlea is located.

Inside the cochlea

Running up and down the length of the cochlea is a tube filled with liquid, called endolymph. The length of tube spiralling in from the stirrup bone is called the scala vestibuli; its return loop is called the scala tympani. Separating the two is the basilar membrane, containing the organ of Corti, which is lined with microscopic sensory hair cells. Vibrations from the ossicle bones ripple through the endolymph, causing these "hairs" to bend. This causes the sensory cells to create nerve signals, which travel along the auditory nerve to the brain.

Balance

Three semicircular canals, set at right angles to each other in the inner ear, help you to balance. Every time your head moves, the flow of liquid within them is picked up by sensory hair cells. These send nerve signals to the brain which can then work out the direction of movement and send instructions to the muscles to adjust the position of the body if necessary.