Peyer's patches

Noduli lymphoidei aggregati (ilei)

Lymphatic & immuneLymphaticsAbdomen

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What it is

Oval, slightly raised plaques of lymphoid follicles in the wall of the last part of the small intestine (ileum), on the side away from the mesentery. Shown here as representative plaques on a loop of ileum in the lower right abdomen; the real gut carries 30-40 of them.

Function

Sample the contents of the gut through specialised M cells and generate IgA-secreting plasma cells that protect the whole intestinal lining.

Size

Each 2-5 cm long and 1-2 cm wide; 30-40 patches, most numerous in the terminal ileum

Clinical note

Typhoid fever ulcerates the patches and can perforate the bowel; they are also the entry point for polio virus and for prions in variant CJD.