You have more tonsils than you think, arranged in a defensive ring
Most people picture two lumps at the back of the throat, but humans are born with four kinds of tonsil forming a ring around the entrance to the airway and gut. Their pitted surfaces trap passing microbes so immune cells can study them, and they are most vigorous in early childhood.
The circle, known as Waldeyer's ring, includes the adenoid high in the throat behind the nose, two small tubal tonsils beside the openings of the Eustachian tubes, the familiar pair of palatine tonsils at the sides of the throat, and lingual tonsils, a cluster of nodules at the base of the tongue. Together they sit exactly where inhaled and swallowed material first meets the body, which makes them sentries for both the respiratory and digestive tracts.
Their structure is built for sampling. The palatine tonsils are riddled with deep crypts that multiply the surface area, and specialised M cells in the lining pass bacteria and viruses inward. Inside, follicles with germinal centres let B cells refine their antibodies, switching the type they make and mutating their genes to improve the fit. The output includes IgA, IgG and IgM; secretory IgA guards mucous membranes before an infection can take hold.
Each part keeps its own timetable. The adenoid grows until about age 5 and begins shrinking by 7. The palatine tonsils peak in absolute size at puberty but are largest relative to the throat in young children; in adults each measures up to about 2.5 centimetres long. Lingual tonsils appear later and stay fairly constant. With age, germinal centre activity drops and the tissue gathers more innate immune cells such as mast cells, matching the shrinkage seen in adulthood.
Enlarged palatine tonsils can make speech sound nasal, and obstruction may matter more in obese children. Tonsil stones, mostly calcium, can grow to the size of a blueberry and smell strongly of hydrogen sulfide. Researchers have even grown tonsil organoids in the lab to watch how Epstein-Barr virus pushes infected B cells into germinal-centre-like states, and found that CD4 T cells held that outgrowth in check.
Source: Tonsil
