The epithelial cells which line these villi have microvilli. The vesicles arise by distention of the chorionic villi by fluid. There is increased trophoblast proliferation and enlarging of the chorionic villi. EC cells are small polygonal cells located in the crypts between intestinal villi. They are covered with small finger-like projections called villi (singular, villus). Chorionic villi (from the embryo) on the embryonic pole grow, forming chorion frondosum. The virus invades and replicates in the villi of the small intestine. Coronavirus infection of the intestinal villi makes the cells more susceptible to parvovirus infection. Smooth muscle fibers may be in the lamina propria, such as in the intestinal villi. Eventually, the syncytiotrophoblasts come into contact with maternal blood and form chorionic villi. EAEC toxins are destructive to the intestinal villi and enterocytes. They generally line the gastrointestinal tract, where they regulate the shapes of crypts and villi. Most of the cells in the connective tissue core of the villi are fibroblasts. It falls to 30 mmHg in the capillaries in the villi. Lacteals are small lymph vessels, and are present in villi.