What Is an Ear and How Does It Function?
Ear is one of a pair of structures found on either side of the head of vertebrates. Ears are concerned with both hearing and balance. The ear is an advanced and very sensitive organ of the human body. The ear’s function is to transmit and transduce sound to the brain through the parts of the ear: the outer ear, the middle ear and the inner ear. The major task of the ear is to detect, transmit and transduce sound. Another very important function of the ear is to maintain our sense of balance.
The only part of the ear that we can see – the outer ear or pinna – locates and directs the sound into the inner ear. Here the sound waves are turned into nerve impulses and are passed to the brain. The sound waves travel from the outer ear and in through the auditory canal, causing the eardrum, or tympanic membrane, to vibrate. This, in turn, causes the three small bones, known as the ossicles, or the hammer, the anvil and the stirrup, in the middle ear to move. The vibrations move via the oval window through the fluid in the cochlea in the inner ear, stimulating thousands of tiny hair cells. This results in the transformation of the vibrations into electrical impulses finally perceived by the brain as sound.
Since the outer ear is the only visible portion of the ear in most animals, the word “ear” often refers to the external part alone. The middle ear includes the tympanic cavity and the three ossicles. The inner ear sits in the bony labyrinth, and contains structures which are key to several senses: the semicircular canals, which enable balance and eye tracking when moving; the utricle and saccule, which enable balance when stationary; and the cochlea, which enables hearing. The ears of vertebrates are placed somewhat symmetrically on either side of the head, an arrangement that aids sound localisation.
Some animals have no external ears, but, of course, this does not mean that they cannot hear. Movements of the head cause fluid in the semicircular canals to swirl over tiny cells within the canals, telling the animals when it is “out of balance”. The ear may be affected by disease, including infection and traumatic damage. Diseases of the ear may lead to hearing loss, tinnitus and balance disorders such as vertigo, although many of these conditions may also be affected by damage to the brain or neural pathways leading from the ear.