American Medical Association Family Medical Guide - American Medical Association [710]
If your symptoms persist and the pain is severe, surgery may be an alternative. Your doctor may remove a small piece of bone from the adjacent vertebra to relieve pressure on the nerve. If several disks are involved, a procedure called spinal fusion may be recommended to permanently immobilize the adjacent vertebrae. It is always a good idea to get a second opinion before having back surgery.
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Disorders of the Ear
The ear is the organ of hearing, and it also plays a role in maintaining balance. It has three parts—the outer ear, the middle ear, and the inner ear. The outer ear includes the part of the ear that we see—folds of skin and cartilage called the pinna—and the ear canal, a passage about ¾ inch long that leads from the pinna to the eardrum. The opening of the ear canal is surrounded by cartilage, which is covered with skin that contains wax-producing glands and hairs. The bone of the deeper part of the canal is lined with a very thin layer of skin. A thin membrane called the eardrum stretches across the inside end of the outer ear canal, separating the outer ear from the middle ear.
The middle ear is a small cavity between the eardrum and the inner ear that is bridged by three small, interconnected bones (the ossicles)—the hammer, the anvil, and the stirrup. The hammer is attached to the inner lining of the eardrum. A ligament (a band of fibrous tissue) attaches the stirrup to an opening (the oval window) that leads to the inner ear. The anvil lies between the hammer and the stirrup and is attached to both.
One of the openings in the middle ear leads into the mastoid portion of the temporal bone (the bone that contains all of the internal structures of the ear). Two openings lead into the inner ear. Another opening, the eustachian tube, leads to the back of the nose. The eustachian tube equalizes air pressure on the inside of the eardrum with the environmental air pressure. Sometimes the eustachian tube becomes blocked and then clears again; this sudden equalization of air pressure feels as if your ear has popped.
The inner ear consists of several fluid-filled chambers—the cochlea (which is involved in hearing) and the semicircular canals and vestibule (which are involved in balance and together form the vestibular labyrinth). The vestibular labyrinth and the cochlea relay hearing and balance information from the inner ear to the brain via the vestibulocochlear nerve.
How the Ear Works
How You Hear
Sound starts as a disturbance of the air, which produces sound waves. The outer ear collects the sound waves and funnels them into the middle ear, which consists of the eardrum, the hammer, the anvil, the stirrup, and the eustachian tube. The sound waves hit the eardrum and make it vibrate. The vibrations then pass into the inner ear, which consists of the semicircular canals, the vestibule, and the cochlea. Tiny hairs that line the cochlea convert the vibrations in the fluid into electrical nerve impulses, which are transmitted to the brain via the vestibulocochlear nerve. The cochlea also transmits information about balance to the brain via the cochlear nerve.
Most sounds reach you through this process, which is supplemented by vibrations that are conducted through the bones of the skull to the inner ear. You hear your own voice mainly through this supplemental type of hearing.
How You Keep Your Balance
Your brain constantly monitors the position and movement of your head and body to enable you to keep your balance. A structure called the vestibular labyrinth in the inner ear monitors the movement of the head by means of three semicircular canals that sit at right angles to each other. Whatever way you move your head—nod it, shake it, or tilt it—at least one of the semicircular canals will detect the movement and relay the information to your