The tonsils (palatine tonsils) are a pair of soft tissue masses located at the rear of the throat (pharynx). Each tonsil is composed of tissue similar to lymph nodes, covered by pink mucosa (like on the adjacent mouth lining). Running through the mucosa of each tonsil are pits, called crypts.

The tonsils are part of the lymphatic system, which helps to fight infections. However, removal of the tonsils does not seem to increase susceptibility to infection. Tonsils vary widely in size and swell in response to infection.