The tonsils are areas of lymphoid tissue on either side of the throat. An infection of the tonsils is called tonsillitis.

As with other organs of the lymphatic system, the tonsils act as part of the immune system to help protect against infection. In particular, they are believed to be involved in helping fight off pharyngeal and upper respiratory tract infections.

Tonsils in humans include, from superior to inferior: pharyngeal tonsils (also known as adenoids), tubal tonsils, palatine tonsils, and lingual tonsils. Together this set of lymphatic tissue is called the tonsillar ring or Waldeyer's ring. Tonsils tend to reach their largest size near puberty, and they gradually undergo atrophy thereafter. However, they are largest relative to the diameter of the throat in young children, and tonsillectomy (surgical removal of tonsils) may be indicated if they are obstructing the airway or interfering with swallowing.

Most commonly, the term "tonsils" refers to the palatine tonsils that can be seen in the back of the throat.

Tonsillitis is an inflammation of the tonsils and will often, but not necessarily, cause a sore throat and fever. In chronic cases tonsillectomy may be indicated.

Tonsilar crypts

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The palatine tonsils include numerous pits and crevices, termed "tonsilar crypts," which often harbor large numbers of bacteria and which serve as a locus of infection. Tonsil crypts are indentations on the tonsil that resemble the pores of the skin.

Macrophages and other white blood cells concentrate by the tonsilar crypts as well, in response to the microorganisms attracted to the crypts. Accordingly, the tonsilar crypts serve a forward sentry role for the immune system, by providing early exposure of immune system cells to infectious organisms which may be introduced into the body via food or other ingested matter.

However, the tonsilar crypts often provide such an inviting environment to bacteria that bacterial colonies may form solidified "plugs" or "stones" within the crypts. In particular, sufferers of chronic sinusitis or post-nasal drip frequently suffer from these overgrowths of bacteria in the tonsilar crypts. These small whitish plugs, termed "tonsilloliths" and sometimes known as "tonsil stones," have a foul smell and can contribute to bad breath; furthermore, they can obstruct the normal flow of pus from the crypts, and may irritate the throat (people with tonsil stones may complain of the feeling that something is stuck in their throat).

Head and neck

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