Palatine tonsil

The palatine tonsils are what almost everyone simply calls the tonsils. They are clusters of lymphoid tissue, the tissue the body's defense system works with, and they sit in the lateral oropharynx, that is on either side of the back of the throat. They are not alone: they are part of Waldeyer's ring, a circle of defensive tissue that also includes the adenoids and the tubal and lingual tonsils.

Their location is no accident. They stand at the door: everything entering through the mouth passes in front of them. They lie right near where the digestive tract and the upper respiratory tract begin, so they meet pathogens, the germs that can cause disease, along with any other material that comes in through the mouth.

That makes them a lookout post. They are mucosa-associated lymphoid tissue, meaning defensive tissue embedded in the moist lining of the throat, and they are the main lymphoid tissue of the oropharynx. Inside they house B lymphocytes, the cells that make antibodies, and there those lymphocytes can mature and produce every immunoglobulin isotype, the different classes of antibody.