Ear- The Sense of Hearing
Humans have two years, one on each side of the head. Human ears are organized for the senses of hearing and balance. The year is a miniature receiver, amplifier, and signal processing system.
Structure of Ear
The human ear is divided into three parts:
- The external ear
- The middle ear
- The inner ear
The External or Outer Ear
It consists of the externally visible part of the ear called the pinna and the internal part, the auditory canal. The auditory canal is the passage reading to the eardrum. The eardrum is also known as the tympanic membrane.
The Middle Ear
The middle ear is a small air-filled cavity. it is separated from the external ear by the eardrum and from the internal ear by a thin bony partition which contains two small openings name the oval window and round window.
The middle ear contains three tiny bones called ear ossicles. These balls are named as malleus incus and stapes.
The handles of the malleus are attached to the internal surface of the eardrum. Its opposite is connected with the incus.
The incus is the intermediate bone and it articulates with the head of the stapes.
The flat part of the stapes fits into the oval window. Directly below the oval window is another opening called the round window.
The round window is covered by a thin membrane. The anterior wall of the middle ear contains an opening that leads directly into the auditory tube. This connects the middle ear with the throat does any throat infection that may lead to the ear through the Eustachian tube. The Eustachian tube also helps in equalizing air pressure on both sides of the eardrum.
The Internal Ear
The internal or inner ear is also called membrane labyrinth. It has two main parts cochlea and semicircular canals.
The cochlea is a hollow, spiral-shaped, chamber. It resembles a snail’s shell. it consists of a bonus spiral canal that makes about 2^3/4 turns around the central bony core. It is in a spiral cavity contains three separate channels or canals that run parallel.
The median canal is filled with endolymph and the outer to canals are filled with a fluid called perilymph.
The middle canal contains a spiral organ called the organ of Corti. The organ of Corti is the organ of hearing. it contains a series of nerve cells and their cells with join the auditory nerve and help in hearing.
The hair cells of the organ of Corti are very sensitive to sound. they can be damaged by exposure to high-intensity noises such as a noise produced by engines of jet planes etc.
The inner ear also contains three semicircular canals. these candles are arranged at right angles to each other in three different planes and are filled with endolymph. One end of each canal is swollen to form an ampulla. the ampulla contains sensory cells that help in the balance of the body while moving. Inner fibers arise from these cells and join the auditory nerve.
There is a short stem called vestibule which joins the semicircular canal and cochlea. It contains two small sacs- the utriculus and sacculus. these also contain tiny hair-like sensory cells that help in the static balance of the body while at rest.