Mechanisms involved in the development of the small intestine mucosal layer in postnatal piglets.

The use of complementary visualization and measurement techniques allowed accurate description and quantification of changes in the intestinal mucosal architecture and provided a comprehensive outlook on the dynamics of remodelling and maturation processes of the mucosal layer taking place in the small intestine of piglets from birth to weaning. The aim of the study was to examine the early postnatal development of the small intestine in pigs. Three techniques were used: scanning electron microscopy (measurements of villus density and shape, height of enterocytes and microvilli, cell exfoliation, and location of extrusion zones), optical microscopy (cross section, measurement of structures: villus length and width; crypt depth; mucosal thickness), and confocal microscopy (cell localization, apoptosis, exfoliation and migration). The postnatal development of the mucosal layer of the small intestine was reflected in changes in the density, length, width, and shape of villi, crypt depth, replacement of enterocyte population, and arrangement. The presence of deep transverse furrows on villus corpus and vacuolated fetal-type enterocytes in the mucosal layer of the small intestine, which are able to engulf large amounts of colostrum shortly after birth, appears to play an important role in the observed phenomenon of straightening of the villus height and increasing of the villus diameter shortly after birth. We hypothesized that the intestinal mucosal layer is compressed before birth and ready to unfold within a short time after birth.