Villi Identification and Function
Villi are small cellular structures in the small intestine that vaguely resemble hairs. The large intestine has similar hair-like projections, but according to cytochemistry.net they are no longer referred to as villi. However, they have no formal name and have the same structure and function as villi, so for the purposes of this article I will characterize them as villi. Villi are made up of epithelial cells (a type of cell that serves a protective role and can be found on the surface of the skin and the linings of other types of cells). Villi are made up of two different kinds of cells: absorptive enterocytes and goblet cells. The goblet cells are responsible for secreting mucus, which lines and protects the intestine, and the enterocytes absorb nutrients. Villi's task is to increase the surface area of the intestines that is able to absorb nutrients. This is critical because the primary function of the intestines is nutrient absorption, so having numerous small villi allows the absorptive surface area to be maximized without making the intestines larger in volume.
There are many ways in which the intestinal villi (and the similar epithelial projections in the colon) can become damaged. In some cases, villus damage occurs because of surgical removal of parts of the small intestine. However, the most common way in which intestinal villi can become damaged or killed is through inflammation. Although intestinal inflammation can occur because of an infection , extensive villi damage often comes because of celiac disease. Celiac disease is a condition of the digestive system in which the immune system responds abnormally to gluten. This lead to inflammation of the areas where gluten is absorbed i.e. the villi of the intestine.
The cells within the villi are constantly in flux, dying off and being replaced. This is natural for most epithelial cells; because their function is, in part, to serve as a protective layer, they are constantly being replaced. Villi damaged or killed will be able to grow back in most cases as long as whatever caused them to die off is taken care of. In celiac disease, this is achieved by stopping the intake of gluten. Once the cause of the damage is gone, the villi will regenerate in a few days.