Question

Describe outer, middle and inner ear.

Answer 1

Outer ear: The outer ear consists mainly of the pinna and the external auditory meatus or auditory canal. The pinna collects sound waves and directs them into the auditory canal. The canal contains fine hairs and glands that produce earwax. Earwax lubricates the canal and traps dust and microorganisms. The canal ends at the tympanum or eardrum, a thin membrane that vibrates in response to sound.

Middle ear: The middle ear is an air-filled cavity containing three small bones called ossicles: malleus, incus and stapes. The malleus is attached to the eardrum, the incus lies between the other two bones and the stapes is connected to the oval window of the inner ear. The ossicles transmit and amplify vibrations from the eardrum to the oval window. The Eustachian tube connects the middle ear with the throat and equalises air pressure on both sides of the eardrum.

Inner ear: The inner ear is a fluid-filled labyrinth consisting mainly of the cochlea, semicircular canals and vestibule.

1. Cochlea: A spiral, snail-shell-shaped structure containing the organ of Corti with auditory receptor cells. It is concerned with hearing. Vibrations entering through the oval window create waves in its fluid and stimulate the receptor cells.
2. Semicircular canals: Three canals arranged in mutually perpendicular planes. Their ampullae contain sensory receptors that detect rotational movements of the head and help maintain dynamic equilibrium.
3. Vestibule: It contains the utriculus and sacculus. Their sensory receptors detect the position of the head and linear movements and help maintain static equilibrium and posture.