And let's take a cross section of the small intestine. We basically get the following diagram. Now, the outer portion, shown in red, is the thick and a thin layer of smooth muscle which is controlled by the autonomic nervous system. And this smooth muscle basically contracts in a wavelike fashion and that creates the process of peristalsis, which basically moves our kind, the food, along our small intestine. Now, the region right below the smooth muscle layer is the epithelial layer. And attached to our epithelial layer, we basically have many of these projections which are known as villi.