Question

Describe the internal structure of human ear with labelled diagram.

Answer 1

The human ear is made up of following three parts:

(1) Pinna or external ear: It is a funnel-shaped structure. Its main function is to focus the sound waves. From the pinna, the auditory meatus extends into the mastoid bone. It contains sebaceous glands which secrete the sebum or ear wax. Next to auditory meatus is the middle ear, the two are separated by means of a tympanum or tympanic membrane or eardrum.

(2) The middle ear: It is in the form of small cavity in connection with the pharynx by means of the eustachian tube. In the middle ear auditory ossicles are present. The auditory ossicles are three specialized bones- malleus (hammer), the incus (anvil) and stapes (stirrup). They transmit sound vibration from the tympanic membrane to the membrane of the oval window.

(3) The inner ear: It consists of three semicircular canals (the organs of equilibrium) and the cochlea (The organ of hearing). The cochlea is spiral shell-shaped hollow structure. It is divisible into three parts, a ventral scala tympani, a dorsal scala vestibule and a cochlear canal present in between them. The cochlear canal is roughly triangular in cross-section resting on the basement membrane and extending all along the length of the cochlear canal is the organ of Corti. It consists of many parallel rows of sensory cells overlined by a tectorial membrane.