Some developmental aspects of the bovine fetal gut.

The morphology of the normal bovine fetal gut has receivec little attention. A more detailed knowledge of its structure is necessary to serve as a basis for studies of pathologic changes in the fetal gut and early postnatal gut in this species. The development of Peyer’s patches, argentaffin cells, and Paneth cells was studied in the bovine fetuses. These were selected because they represent specific identifiable structures and because knowledge of their normal status is essential to the interpretation of pathologic changes in the gut. Peyer’s patches are circumscribed patches of lymphoid tissue containing more than five follicles (15). They occur on the side of the intestinal wall opposite to the mesenteric border and are visible with the naked eye. They consist of dense lymphoid tissue with large lymphocytopoietic or reaction centers in their interior. Their periphery is marked by a thin layer of condensed reticular fibers. They are located primarily in the submucosa but often reach the mucosal lamina propria. Their number in the various parts of the bovine intestine has never been accurately determined, but most anatomy textbooks place the total number a t from 18 to 40 in adult cattle and 20 to 58 in calves (33). In the fetal gut, Peyer’s patches produce lymphocytes and act as hematopoietic centers. Argentaffin cells, also known as basal granular, enterochromaffin, or Kultschitzky cells, arise from endoderm (25). Although this study is limited to the small and large intestines, these cells are distributed throughout the epithelia of the alimentary tract, also including the esophagus, the stomach, and perhaps the gall bladder and pancreas (24, 28). They were first described in 1870 by HEIDENHAIN (14) in canine and lapine gastric epithelium and in 1879 by GRUTZNER and MENZEL (12) in the epithelium of the human small intestine. Subsequently, these cells have been found to be widely distributed in the animal kingdom, but their frequency varies between mammalian species.