The mucosal surface of the jejunum had villi of variable height. The villi were having a broad base with tapering to blunt ends (Fig. 1a) as reported in the Egyptian goats (Hassan and Mousaa, 2015) where the villi were fingershaped with pointed apexes as reported in young pigs (Skrzypek et al., 2005), calves (Pearson et al., 1978; Po et al., 2005), dogs (Johnson et al., 1986) and humans (Marsh and Swift, 1969). These were long and flat in calves (Dubourguier et al., 1978). Some villi were having inclined apexes probably due to more length of the ends. The surface of the villi showed slight corrugation in the initial part of the jejunum (Fig. 1b). These corrugations were very faint in this region and also showed orifices for goblet cells. The apex of the villi showed a scaly appearance with very few goblet cells as also reported in goats (Hassan and Moussa, 2015). There were 3-4 crypt openings surrounded each villus (Figs. 1a,1b). As many as 20 crypts may surround each villus (Cocco et al., 1966), but a functional ratio of three crypts to one villus had been proposed in humans (Loehry and Creamer, 1969). The structural changes in the form of more prominent corrugations on the villi surface and density of villi were also increased towards the caudal aspect of the jejunum (Figs. 1c,1d). The corrugations were deep, irregular clefts cutting into the side of the villus and dividing it into separate islands of tissue. The majority of these corrugations tended to run in a horizontal direction, similar observations were also reported in goats (Hassan and Mousaa, 2015).

Young pigs also showed a similar pattern in the form of transversal furrows (Skrzypek et al., 2005) and calves (Dubourguier et al., 1978). The corrugations end abruptly and did not form a continuous system of clefts. At higher magnification, the villi surface showed hexagonal-shaped enterocytes and there was the presence of dense mat of microvilli throughout the villi surface (Figs. 2a,2b) as observed in young pigs (Skrzypek et al., 2005). They also revealed that the villi surface had raised convex domeshaped structures at places towards the apex which were similar to the findings of the present study. At some regions where desquamation of upper surface took place presented the underlying submucosa and columnar cells were also seen in this region (Fig. 2c). The villi surface showed orifices with irregular boundaries for openings of goblet cells (Figs. 2b and 2d) in between the dense areas of the microvilli. There was the presence of some areas which were devoid of microvilli which were also observed in young pigs (Skrzypek et al., 2005). Towards the basal part of the villi, there was the presence of crypts or openings of intestinal glands.

The epithelium of the jejunum was made up of columnar and goblet cells but no Paneth cells were observed in the villous part as reported in gnotobiotic dogs (Johnson et al., 1986). They also reported a single large or multiple moderate sizes, membrane-bound, supranuclear, cytoplasmic vacuoles. The columnar cells were with the well-marked microvilli (Figs. 3a and 3b). The microvilli contained a core made up of fine filaments forming thick bundles which extended deeply into the terminal web of the apical cytoplasm as reported in lambs (Gray et al., 1980) and mice (Mukherjee and Williams, 1967). The columnar cells were joined at the apical surface by typical junctional complexes. The mitochondria of different shapes were abundant in number in the apical part of the cytoplasm (Fig. 3b) and their size appeared to be slightly more as reported in gnotobiotic dogs (Johnson et al., 1986) and lambs (Gray et al., 1980). A very few goblet cells were interspersed in between the columnar cells. The cytoplasm of goblet cells was distended with mucus granules. The nucleus was located towards the base, granular endoplasmic reticulum and mitochondria were also present in the supranuclear part of the cytoplasm as observed in mice (Mukherjee and Williams, 1967).

The cryptal epithelium consisted of columnar, Paneth, endocrine and goblet cells. The columnar cells possessed luminal microvilli, nuclei placed towards the base and polymorphic mitochondria were as compared to the surface epithelial cells as reported in gnotobiotic dogs (Johnson et al., 1986). The microvilli appeared less numerous and short than those in enterocytes. The junctional complexes were also observed along with free ribosomes, Golgi bodies in the apical cytoplasm.

The Paneth cells were accumulated at the base of the crypts. They were pyramidal-shaped cells with their broad base resting on the basement membrane and narrowed towards the apical end. The osmiophilic granules located towards the apical portion of the cytoplasm also contained granular endoplasmic reticulum and Golgi bodies (Fig. 3c) and this was in agreement with the findings in sheep (Ergun et al., 2003). The enterochromaffin cells were observed in the present study but their occurrence and number were decreased. These cells showed electrondense osmiophilic granules which were infranuclear in position in the cytoplasm (Fig. 3d) as reported in calves (Pearson and Logan, 1983) and other mammalian species (Dawson, 1970; Carvalheiar et al., 1968) and equine small intestine (Takehana et al., 1998) and several studies had been carried out in various animals (Satoh et al., 1990). The goblet cells were fewer in the epithelium of the crypts. They were generally flanked by the columnar cells through occasional goblet cells and Paneth cells were found. The cytoplasm was appeared dark as compared to the adjacent cells and their nucleus was pushed towards the base and granular endoplasmic reticulum and mitochondria were also observed as reported in humans (Kelley, 1973) and mice (Mukherjee and Williams, 1967). The goblet cells were scattered throughout the villus epithelium in lambs (Gray et al., 1980).