Mark Gannett, age 14, of Austin, Tex., for his question:

WHAT IS AN ADENOID?

An adenoid is any of a number of masses of tissue found high in the back of the throat behind the nose. They work and look a lot like lymph nodes and tonsils.

The adenoids serve a good purpose. They catch and destroy many of the germs that come into the nose and throat, just as tonsils do. If there are too many germs, the adenoids may become swollen and inflamed. Then the lymph cells multiply, making the adenoids even larger. If the infection continues, the adenoids may stay enlarged.

Tonsils can be enlarged without blocking the throat, but the adenoids are in a smaller place and when they enlarge, they can completely block the nasal passage. This often happens with children.

Often problem adenoids force a child to breathe through the mouth. Doctors sometimes then correct this condition by removing the adenoids surgically.