Adenoids are a mass of lymphoid tissue situated at the very back of the nose (the nasopharynx).
These folds of lymphatic tissue are much like a mat of tiny lymph nodes.
Adenoids are studded in the roof of a passage called the nasopharynx (where the nose blends into the mouth).
Adenoids are sometimes called the nasopharyngeal tonsils.
Normally, in children, they make a soft mound in the roof and posterior wall of the nasopharynx, just above and behind the uvula.
Adenoids are part of the immune system.
Like all lymphoid tissue, they trap infectious agents like viruses and bacteria, and they produce antibodies.
Since the adenoids are located at the back of the nasal airway, they provide defense against inhaled substances.