The Human Ear Diagram, Structure and Its Function

The Human Ear Diagram :



The human ear diagram, internal structure of ear, human ear structure and function, human ear diagram


 

Human Ear Structure :

The ear is divisible into three parts for the purpose of description, namely

1.  External Ear
2.  Middle Ear
3.  Internal Ear

1. External Ear :

The external ear is characteristic in mammals including man. It consists of an expanded portion, the pinna and a canal called external auditory meatus.

(a) Pinna :

The pinna is attached on either of the head and it is a flap like cartilage covered with the skin. In many mammals it is movable in various directions due to the presence of special muscles which is under the control of the animal. But in human, it is not movable. The pinna helps in receiving sound waves and in determining the direction of sound.

(b) External auditory meatus :

It is a tubular canal which leads from pinna to the tympanic membrane. Tympanic membrane is also called as tympanum or ear drum. In the skin of outer part of the external auditory meatus, the cerminous glands are located, which secrete cerumen (ear wax). These glands are modified sweat glands.

2. Middle Ear :

The middle ear is also called tympanic cavity which is located between tympanum and internal ear. It is an air filled cavity, lined by mucous membrane. Its lateral wall contains a large opening which is closed by tympanic membrane.

Eustachian tube :

The middle ear communicates with the pharynx by means of eustachian tube or auditory tube. This tube serves as an air channel by which the air tension in the middle ear can be equalised with atmospheric pressure. In other words, the air pressure on both sides of the tympanic membrane is equalised by this tube. Hence it acts as a safety valve. It also works as an avenue of drainage of the middle ear.

Ear ossicles :

There is a chain of three ear ossicles found in the tympanic cavity. These are malleus, incus and stapes.

Malleus :

It is a hammer shaped bone and is fixed to the eardrum on one side. It is attached with the incus by a synovial hinge joint at the other side. 

Incus :


This bone is anvil shaped and remains in the middle. It joints with the malleus and is also connected with the stapes at its long process by ball and socket joint.

Stapes :


It is stirrup shaped. It has a foot plate which is fixed into the fenestra ovalis or fenestra vestibule. The fenestra ovalis is the oval window of the inner ear. These ossicles transmit the air borne vibrations falling upon the eardrum into the internal ear through their mechanical movements. There are two windows present in the inner wall of the middle ear which lead to internal ear. These are fenestra ovalis and fenestra rotunda which are covered with tough membrane.

3. Internal Ear :


The internal ear is represented by membranous labyrinth which is enclosed by a bone, known as periotic bone . This bone assumes the shape of the membranous labyrinth is filled with a fluid, known as perilymph which is lymph like and colourless fluid. The different parts of membranous labyrinth are utriculus, sacculus, endolymphatic duct, semicircular canals and cochlea.


Utriculus, sacculus and endolymphatic duct :

Sacculus is the lower enlarged chamber and utriculus is the upper enlarged chamber. Both Chambers are connected with each other. From the utriculus arises three long, narrow semicircular canals. 

Semicircular canals :


The semicircular canals join with the utriculus by their both ends and they are at right angles to each other. They are named as external, anterior or posterior semicircular canals. Out of these, the anterior and posterior semicircular canals originate from the utriculus as a common canal.

Cochlea :


It constitutes membranous cochlea and bony cochlear canal containing perilymph. Cochlea means snail which forms coils in man around a hollow conical central pillar. 

The human ear diagram, internal structure of ear and function.









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