Ear

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Ear

The ear is the organ that lets us hear and, in humans, helps us keep our balance. It has three parts: the outer ear, the middle ear, and the inner ear.

Outer ear
The visible part is called the auricle or pinna, and it includes the ear canal that leads to the eardrum. The outer ear collects sounds and shapes how we hear them. Earwax in the canal helps keep the ear clean by moving outward on its own. The muscles in the outer ear are small in humans and don’t move the ear much, but they can move in some other animals.

Middle ear
The eardrum (tympanic membrane) separates the outer ear from the middle ear. When sound makes the eardrum vibrate, three tiny bones—the hammer (malleus), the anvil (incus), and the stirrup (stapes)—pass and amplify the vibrations to the inner ear. The middle ear is connected to the throat by the Eustachian tube, which helps equalize pressure. The stapes sits on a membrane called the oval window, moving fluid in the inner ear as it vibrates.

Inner ear
The inner ear sits in the temporal bone and includes the vestibular system for balance and the cochlea for hearing. The balance parts are the utricle, saccule, and three semicircular canals, which sense head motion and help keep our gaze steady when we move. The cochlea is a spiral, fluid-filled organ where hair cells convert sound vibrations into nerve signals. These signals travel via the vestibulocochlear nerve to the brain, where we “hear.”

How we hear
Sound travels through the outer ear to the eardrum. The three tiny bones in the middle ear amplify the sound and send it to the inner ear. The fluid in the inner ear moves, bending hair cells in the cochlea. This creates electrical signals that reach the brain and are interpreted as sound. Humans typically hear from about 20 Hz to 20,000 Hz.

Balance and motion
Static balance lets us sense gravity through the utricle and saccule. Dynamic balance uses the semicircular canals to detect head movement, helping us keep our eyes on a target while we move.

Development
During early life, the ear forms from different parts of the developing head and neck. The outer ear develops from the first pharyngeal cleft, the middle ear from the pharyngeal pouches, and the inner ear from otic placodes. The three auditory bones form early in development and help us hear.

Common problems
- Conductive hearing loss: problems in the outer or middle ear, such as earwax blockage, a perforated eardrum, or stiff or missing ossicles.
- Sensorineural hearing loss: problems in the inner ear or along the hearing nerve, often from long-term noise exposure or illness.
- Otitis media (middle-ear infection), ear injuries, or a perforated eardrum.
- Tinnitus: ringing or other sounds heard without external noise.
- Hyperacusis: sounds feel painfully loud to some people.

Treatments
- Earwax removal, antibiotics for infections, or other medical care as needed.
- Tympanoplasty or ossicle repair to fix middle-ear problems.
- Hearing aids for some types of hearing loss.
- Cochlear implants for severe sensorineural loss.
- Protection from loud noise to prevent future damage.

Ear health and care
Protect ears from loud sounds, keep ears clean, and seek medical advice for persistent pain, drainage, sudden hearing loss, or ringing that lasts more than a short time. Ears are delicate but essential for both hearing and balance, shaping how we experience the world around us.