Ear anatomy: function and parts of the ear

Unless you are one of the 466 million people in the world with hearing loss, it’s easy to take your hearing for granted. But losing your hearing can be life-changing in ways you may not expect. That’s why understanding more about your hearing, including the anatomy of your ears, can help you protect your hearing health.

Your ear is a sensory organ that enables you to hear sound. Hearing is the perception of sound energy via the brain and central nervous system. It consists of understanding what the sound is and where the sounds come from.

Your ear is divided into three main parts:

• The outer ear
• The middle ear
• The inner ear

The outer ear is the external part of the ear, which consists of the auricle, also known as the pinna, and the ear canal. It acts like a funnel, gathering sound energy and focusing it on the eardrum.

The pinna is the visible protruding skin-covered flap that gathers sound waves and channels them down your external ear canal through the pinna.

Your ear canal is supported by cartilage at its opening and by bone for the rest of it. The canal is lined with skin and contains glands that produces a discharge which mixes with dead skin cells to make earwax. This earwax, along with the fine hairs at the entrance of the ear canal, helps stop airborne particles reaching inside your ear canal.

Your middle ear is situated between the external and inner parts of your ear. It’s separated from the ear canal by the eardrum or tympanic membrane. The function of the middle ear is to transfer the vibrations from the eardrum to the inner ear fluid. This happens through three small movable bones called ossicles. They extend across the middle ear and corresponding small muscles.

The tympanic membrane is your eardrum which is a thin layer of tissue in the ear that receives sound vibrations and transmits them to the auditory ossicles (small bones in the middle ear). For the membrane to be able to freely move when air hits it, the air pressure on both sides of the eardrum must be the same. Excessive pressure on either dulls your sense of hearing as the membrane cannot freely vibrate.

The tympanic cavity holds three tiny bones known as the auditory ossicles which connect the eardrum to the inner ear. These are called malleus, incus and stapes. When the eardrum vibrates in response to air waves, the inner ear bones are set into motion at the same frequency. This movement is transmitted to a structure in the ear called the oval window, leading to pressure applied with each vibration. This generates wavelike movements of the inner ear fluid at the same frequency as the original sound wave.

There are also two very small muscles in the tympanic cavity: the stapedius stabilizes the stapes, while the tensor tympani dulls loud sounds and converts sound-wave vibrations into inner ear fluid movement.

Your inner ear is the deepest part of your entire ear and it is situated in a bony area called the labyrinth. This is maze-like passageway of bones is lined with a network of fleshy tubes called the membranous labyrinth. Between the bony and membranous labyrinth is a cushion of fluid called the perilymph. There is also a fluid called endolymph. Within the inner ear is also a chamber known as the vestibule which plays a key role in your sense of balance.

The cochlea is what converts sound vibrations to hearing. It forms a snail-like spiral, and winds around a section of sponge-like bone called the modiolus. Shaped like a screw, the modiolus threads from a spiral platform that supports the cochlea.

The organ of Corti is the sensitive part of the inner ear that acts like your body's microphone. It is located on the basilar membrane in one of the cochlea’s three compartments. It contains four rows of hair cells protruding from its surface.

The external acoustic meatus, also known as the ear canal, is the tube-like structure that extends from the outer ear (pinna) to the eardrum (tympanic membrane). It serves as a pathway for sound waves to travel from the external environment to the middle ear, where they are converted into vibrations that the brain can interpret as sound. The external acoustic meatus is lined with skin, tiny hairs, and ceruminous glands that produce earwax, which helps protect the ear by trapping dust and debris. Its curved shape also aids in amplifying sound, while its anatomy helps shield the eardrum from potential damage.