Other than being organs for hearning the ears also help maintain the balanced of the body. Each ear has three parts –the external ear, middle ear and inner ear.

The external ear

This consists of the pinna and the auditory canal. The pinna, the visible part of the ear, is a flap of cartilage situated outside the head. It leads to the tube like auditory canal, which directs sound to the eardrum. The eardrum is a delicate, circular membrane, which vibrates with the pressure of the sound waves strikes it.

The middle ear

The vibrations of the eardrum travel into the middle ear, ad small cavity filled air, and this cavity is called the tympanic cavity. A chain of (anvil) and stapes (stirrup) lies across the middle ear. These bones increase the pressure of the vibrations traveling to the inner ear.

The middle ear is connected to the pharynx by the Eustachian tube. The opening of this tube is usually shut. It opens during swallowing. It also opens to ensure that the air pressure in the middle ear is the same as that on the other side of the eardrum. This allows the eardrum to vibrate freely. From the middle ear the vibrations travel to the inner ear.

Inner ear

The inner ear is filled with fluid. It contains the cochlea and three semicircular canals. The cochlea is a spirally coiled chamber that is vital in receiving sound. It contains thousands of sensory hairs which act as sound receptors. When sound waves cause the fluid of the cochlea to vibrate, the sensory hairs produce nerve impulses. The nerve impulses travel through the auditory nerve, which connects the inner ear to the brain, and are processed in the cerebrum.

The semicircular canals are responsible for maintaining the balance of the body.

The tongue

The receptors for taste located mostly on the tongue. They are slender cells with tiny hairs, and are packed in groups called taste buds. They are stimulated to produce impulses when food (in solution from) reaches them through pores. The nerve fibers connected to the taste buds carry the impulses to the brain, where the taste is interpreted.

The tongue can detect just four basic tastes –sweet, bitter, sour and salty. The other tastes we perceive are a mixture of these four. Different parts of the tongue are more sensitive to different tastes. For example, the tip is more sensitive to sweet.



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