What Is Middle Ear Infection?

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Understanding how the ear works

The ear is divided into 3 parts: the outer ear, the middle ear, and the inner ear.

The middle ear is a small space between the outer and inner ear. It is separated from the outer ear by the eardrum. It contains three delicate bones (the hammer, anvil, and stirrup) that are important in hearing.

Here is how hearing works:

• Sound creates vibrations in the air that are picked up by the eardrum.

• When the eardrum vibrates, the tiny bones inside the middle ear also vibrate, transmitting the vibrations across the middle ear to the inner ear.

• This causes fluid in the inner ear to move.

• When fluid moves in the inner ear, it stimulates the nerve cells inside this part of the ear.

• These nerve cells then send impulses to the brain along the "hearing nerve," and we then hear the sound.

Tubes called the eustachian tubes connect the middle ear to the back of the throat. When functioning properly, the eustachian tubes do the following:

• Equalize air pressure on both sides of the eardrum. When you yawn or swallow and your ears "pop," it is your eustachian tubes adjusting the air pressure in your middle ear. Negative air pressure in the middle ear causes pain and a "full" sensation in the ear.

• Allow drainage from the middle ear to the throat.

• Protect the middle ear from germs that may enter the throat.

Facts About Middle Ear Infection

• Half of all children have at least one ear infection by the time they are 3 years old.

• The earlier a child has a first ear infection, the more susceptible the child is to having others.

• Babies who breast-feed for more than 6 months have fewer ear infections than babies who begin bottle-feeding before they are one month old.

• Children who are exposed to smoking at home tend to have more ear infections.

• After age 5, nearly all children have outgrown their susceptibility to ear infections.

• Middle ear infection is more common in boys than girls.

• Middle ear infection occurs with greater frequency in children attending daycare centers.

• Middle ear infection is most common in winter, less common in summer.

• Children with middle ear infections are more likely to have family members who also have middle ear infections.

• Middle ear infection is more common in American Indians, Alaskan and Canadian Eskimos, and Australian Aborigines