An ultrastructural and cytochemical study of developing small intestine in man

The observations and results of this study suggest that intestinal absorptive cells possess structural and enzymic potential for function in utero. As early as the tenth postfertilization week, microvilli are differentiated, a surface coat is elaborated, alkaline phosphatase activity is localized on microvillar borders, and colloidal particles when introduced into the gut lumen in vitro are transported in vesicles from the apical cell surface to the lamina propria via extracellular spaces. In addition, cytoplasmic lipid droplets appear after administration of corn oil by injection into the gut lumen. However, the term ‘potential’ is stressed in that one can only speculate at present on what materials are absorbed from swallowed amniotic fluid in man.