Ans. EAR
Hearing is as important as is vision.
Role of Ear
Our ear helps us in hearing and also to maintain the balance or equilibrium of our body.
Parts of Ear
Ear has three main parts i.e. external ear, middle ear, and internal ear.
A) External Ear
Division of External ear
External ear consists of pinna, auditory canal and ear drum (tympanum).
Pinna is the broad external part, made of cartilage and covered with skin. It helps to direct sound waves into auditory canal. There are special glands in the walls of auditory canal, which produce wax. The wax and the hairs in auditory canal protect ear from small insects, germs and dust. In additions to this, is helps to maintain the temperature and dampness of auditory canal. Auditory canal ends in ear drum. This thin membrane separates external ear from middle ear.
B) Middle Ear
Middle ear is a chamber after external ear. Three small bones, called middle ear ossicles, are present in a chain in middle ear. These movable bones include malleus, incus and stapes. Malleus is attached with ear drum, and then
Figure 12.10 Structure of human ear
Semicircular canals
comes incus and finally stapes that is connected with a membrane called oval window. Oval window separates middle ear from inner ear. Middle ear also communicates with the nasal cavity through Eustachian tube. This tube regulates the air pressure on both sides of ear drum, figure 12.10
C- Inner Ear
Division of inner ear
Inner ear consists 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. Figure 12.11