Histological and ultrastructural studies of the marsupial Didelphis albiventris Peyer's patches.

Differing from the studied Eutheria the white belly opossum Peyer's patches do not present a conspicuous dome. M cells are located in the inner layer of bilaminal formed at the bottom of the villi. A great variation in the morphology of M cells was observed. The enterocytes located at the epithelial inner layer may present endocytic vesicles, and the microvilli are shorter than the microvilli of enterocytes lining the small intestine. As these morphological aspects have been described to exist in the enterocytes of the lactent opossum small intestine it was surmised that the opossum Peyer's patches special epithelium could represent the persistence in adult animals of a cellular pattern established before the intestinal maturation had occurred.