The ear is comprised of three main sections, including the outer ear, middle ear and inner ear.
The Outer Ear
The outer ear consists of the pinna (the portion that can be seen), the ear canal, and the tympanic membrane (eardrum). The pinna is comprised mostly of cartilage and functions to funnel sounds down into the ear. The ear canal is approximately 2.5 cm in length, 5-7 mm in diameter, and consists of ceruminous glands in the outer 1/3. These cerumenous glands function to produce cerumen or ear wax. The tympanic membrane is transparent and cone shaped in appearance, is 55 to 90 mm2, and stretches across the entrance to the middle ear.
The Middle Ear
The middle ear is a 2 cm3 air filled cavity lined with a mucous membrane, houses 3 middle ear bones: the malleus (hammer), the incus (anvil), and the stapes (stirrup), and connects to the upper part of the throat via the Eustacian tube. The middle ear bones are the smallest bones in your body. Simplistically, the middle ear functions to transmit and amplify the sound waves from the air filled outer ear to the fluid filled inner ear, the organ of hearing.
The Inner Ear
The inner ear has two primary functions: balance and hearing. The semicircular canals and the vestibule are responsible for the balance system while the cochlea is responsible for the hearing system. The cochlea is a fluid filled snail shaped organ that is 2 ¾ turns and 35 mm in length, contains thousands of tiny hair cells. These hair cells are displaced by the incoming sound waves and function to convert the sound waves from the outer and middle ear into electrical impulses for interpretation by the brain via a number of chemical reactions.