ear, nose, and throat disorders
Ears
Inner Ear
The inner ear (labyrinth) is a complex structure consisting of two major parts: Cochlea: The organ of hearing Vestibular system: The organ of balance The cochlea, a hollow tube coiled in the shape of a snail's shell, is filled with fluid. Within the cochlea is the organ of Corti, which consists, in part, of about 20,000 specialized cells called hair cells. These cells have small hairlike projections (cilia) that extend into the fluid. Sound vibrations transmitted from the ossicles in the middle ear to the oval window in the inner ear cause the fluid and cilia to vibrate. Hair cells in different parts of the cochlea vibrate in response to different sound frequencies and convert the vibrations into nerve impulses. The nerve impulses are transmitted along fibers of the cochlear nerve to the brain. The round window is a small, membrane-covered opening between the fluid-filled cochlea and the middle ear. This window helps dampen the pressure caused by sound waves in the cochlea. Despite the protective effect of the Middle Ear , loud noise can damage and destroy hair cells. Once a hair cell is destroyed, it does not regrow. Continued exposure to loud noise causes progressive damage, eventually resulting in hearing loss and sometimes noise or ringing in the ears ( The vestibular system consists of Two fluid-filled sacs called the saccule and the utricle Three fluid-filled tubes called the semicircular canals These sacs and tubes gather information about the position and movement of the head. The brain uses this information to help maintain balance. The saccule and utricle contain cells that sense movement of the head in a straight line, that is, back and forth or up and down. The semicircular canals are three fluid-filled tubes at right angles to one another that sense rotation of the head. Rotation of the head causes the fluid in the canals to move. Depending on the direction the head moves, the fluid movement will be greater in one of the canals than in the others. The canals contain hair cells that respond to this movement of fluid. The hair cells initiate nerve impulses that tell the brain which way the head is moving so that appropriate action can be taken to maintain balance. If the semicircular canals malfunction, which can occur in an upper respiratory infection or other temporary or permanent disorder, the person's sense of balance may be lost or a false sensation of moving or spinning ( Dizziness and Vertigo ) may develop. 