mucosal villus

In anatomy, a villus is a small, slender, vascular projection that increases the surface area of a membrane. The most significant villous membranes are the placenta and the mucous membrane lining the small intestine.

In the small intestine, villi project into the intestinal cavity, dramatically increasing the surface area for food absorption. These villi give the intestinal wall a velvety appearance and are densely packed, with 10 to 40 per square millimeter. Each villus contains blood vessels, a lymphatic capillary (lacteal), muscle, and connective tissue. Blood vessels transport absorbed proteins and carbohydrates, while the lacteal collects emulsified fats. The surface of each villus is covered by columnar cells that absorb nutrients and goblet cells that secrete mucus. Additionally, microvilli, tiny projections on the columnar cells, further amplify the absorptive surface area.