The human ear and its structure in detail
Hearing is an important as visions. Our ear helps us in hearing and also maintain the balance or equilibrium of our body. The ear has three main parts i.e. external ear, middle ear and internal ear.
A:external ear
The external ear consist of pinna, auditory canal and ear drum (tympanum). Pinna is the broad external part, made of cartilage and covered the skin.it helps to direct sound waves into auditory canal. There are special glands in the walls of the auditory canal, which provide wax. The wax and the hairs in the auditory canal protect the ear from small insects, germs and dust particles.in addition to this, they help to maintain the temperature and dampness of the auditory canal. The auditory canal ends in the ear drum. This thin membrane separates the external ear from the middle ear.
B:-middle ear
Middle ear is a chamber after the external ear.
Three small bones, called middle ear ossicles, are also present in a chain in
middle ear. These movable bones includes melleus, incus and stapes. Malleus is
attached with ear drum, then comes incus and the finally the stapes comes that
is connected with a membrane called oval window.oval window separates middle ear
from inner ear.middle ear also communicate with the nasal cavity through
Eustachian tube.this tube regulates the air pressure on both sides of ear drum.
C:-inner ear
The inner ear consist of three parts i.e
vestibule, semicircular canals and cochlea. Vestibule is present in the centre of
inner ear. Three canals called semicircular canals are posterior to the vestibule.the
cochlea is made of three ducts and wraps itself into a coiled tube. Sound receptor cells are present within the middle duct of cochlea.
The process of hearing
The pinna of the external ear focuses and direct
sound waves into the auditory canal. The sound waves strike the ear drum and produce
vibration in it. From the ear drum, the vibrations strikes the middle ear and produce
further vibrations in malleus, incus and then stapes. From stapes, the vibrations
strikes the oval window and then reach the fluid-filled middle duct of cochlea.
The fluid of cochlea is moved and receptor cells are stimulated. The receptor
cells generates a nerve impulse, which travels to the brain and is interpreted as
sound.
Ears maintain the balance of body
Semicircular canals and vestibule help to
maintain the balance of the body. Semicircular canals contain sensory nerves
which can detect any movement of head. Vestibule can detect any changes in
posture of body. The neurons coming from these two receptors reach the cerebellum through the auditory nerve.
Characteristics of sound
A thunderstorm is characterized by the presence
of lightning and a thunder. The lightning is caused by an electrical charge due
to the movement of water drop lets or crystals carried by wind. The sudden
increase in pressure and temperature from lightning produce rapid expansion of the air. This expansion of the air produces a sound of thunder. The flash of
lightning is followed after some seconds by a roar of thunder. This time
difference is due to the fact that light travel slower than sound.
Sound less world
Deafness is a state in which hearing is not
possible. The defect of ear drum, cochlea, middle ear ossicles, or auditory nerve
may cause deafness. Infection in Eustachian tube may spread to middle ear
too. Ear drum may be damage by an infection in auditory canal. Excessive noise,
strong blows on the cheek, pointed objects entering auditory canal and attack from
insects may also affect hearing.
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