Question

human ear diagram and function​

Answer 1

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The ear's function is to transmit and transduce sound to the brain through the parts of the ear: the outer ear, the middle ear and the inner ear. The major task of the ear is to detect, transmit and transduce sound.

The function of the outer ear is to collect sound waves and guide them to the tympanic membrane. The middle ear is a narrow air-filled cavity in the temporal bone. It is spanned by a chain of three tiny bones—the malleus (hammer), incus (anvil), and stapes (stirrup), collectively called the auditory ossicles.

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Answer 2

Structure of Ear:

Each ear consists of three portions:

(i) External ear,

(ii) Middle ear and

(iii) Internal ear.

Functions of External Ear:

It directs sound waves towards the tympanic membrane. The sound waves produce pressure changes over the surface of the tympanic membrane. The cerumen (ear wax) prevents the entry of the foreign bodies into the ear.

Functions of Middle ear:

(i) Due to the pressure changes produced by sound waves, the tympanic membrane vibrates, i.e., it moves in and out of the middle ear. Thus the tympanic membrane acts as a resonator that reproduces the vibration of sound,

(ii) It transmits sound waves from external to the internal ear through the chain of ear ossicles,

(iii) The intensity of sound waves is increased about twenty times by the ear ossicles. It may be noted that the frequency of sound does not change and

(iv) From the tympanic cavity extra sound is carried to the pharynx through Eustachian tube.

Functions of Ear:

The ear performs the functions of hearing and balancing (equilibrium).

1. Mechanism of Hearing:

The sound waves are collected by the external ear up to some extent. They pass through the external auditory meatus to the tympanic membrane which is caused to vibrate. The vibrations are transmitted across the middle ear by the malleus, incus and to the stapes bones. The latter fits into the fenestra ovalis. The perilymph of the internal ear receives the vibrations through the membrane covering, the fenestra ovalis.

From the perilymph the vibrations are transferred to the scala vestibuli of cochlea and then to scala media through Reissner’s membrane. Thereafter, the movements of endolymph and tectorial membrane stimulate the sensory hairs of the organ of Corti.

The impulses thus received by the hair cells are carried to the brain (temporal lobe of each cerebral hemisphere) through the auditory nerve where the sensation of hearing is felt (recognised).

Conduction of Sound Vibrations in the Ear

It is evident that the external and middle ears serve to transmit sound waves to the internal ear. It is in the internal ear that the transformation of the vibrations into nerve impulses for relay to the brain takes place. During loud sound, some sound waves are transferred from scala vestibuli to scala tympani through helicotrema.

From scala tympani the sound waves are transmitted to the tympanic or middle ear cavity through the membrane covering the fenestra rotunda. From the tympanic cavity the sound waves are transferred to the pharynx through the Eustachian tube.

2. Equilibrium:

The semicircular canals, utricle and saccule of membranous labyrinth are the structures of equilibrium (balancing). Whenever the animal gets tilted or displaced the hair cells of the cristae and maculae are stimulated by the movement of the endolymph and otolith.

The stimulus is carried to the brain through the auditory nerve and the change of the position is detected by the medulla oblongata of the brain. After that, the brain sends impulses (mes­sages) to the muscles to regain the normal conditions.