The development of the ovine small intestine.

Intestinal development was noted from 27 days gestation. By 50 days gestation the ovine small intestine shows the beginning of villus formation. The lumen becomes patent by 70 days. Proximal regions mature earlier than distal regions. Vacuolation of enterocytes occurs in all regions of the small intestine at some stage during development. Mature-looking enterocytes can be found in proximal regions by 125 days gestation while in distal regions immature vacuolated cells can still be found just prior to birth. Enterocytes lining the villi are more mature at the villus tip than those at the base in all regions. This gradient of maturation is consistent with a suggestion of the early establishment of adult patterns of proliferation and migration of enterocytes in the sheep fetus.