Ears

The ears are the organs of hearing and balance in humans and many animals. They detect sound and help sense head position and movement, contributing to communication, safety, and navigation.

Anatomy and structure involve three main regions. The outer ear contains the pinna (the visible part) and the external auditory canal, which channel sound toward the eardrum. The middle ear is an air-filled cavity that houses three tiny bones—the malleus (hammer), incus (anvil), and stapes (stirrup)—which transmit and amplify vibrations from the eardrum to the inner ear via the oval window. The inner ear contains the cochlea, which converts mechanical vibrations into neural signals for hearing, and the vestibular system, including the semicircular canals and otolith organs, which detect head rotation and linear acceleration to help maintain balance.

Functionally, hearing begins when sound waves strike the eardrum, causing it to vibrate. These vibrations move the ossicles, which transfer motion to the cochlear fluids. Hair cells in the cochlea convert this mechanical energy into electrical impulses that travel through the auditory nerve to the brain. Balance depends on fluid movement within the semicircular canals and the otolith organs, which relay information about head position and motion.

Development and health factors influence ear function. Ears develop before birth and are present in most vertebrates. Common human conditions include middle-ear infections (otitis media), wax buildup, and various forms of hearing loss (conductive or sensorineural), as well as tinnitus. Protective features include earwax that traps debris and reflexive responses that modulate exposure to loud sounds.