Two of the major functions of the alimentary canal (essentially the pathway from the mouth to the anus, mostly encompassing the stomach and intestines) are digestion and assimilation. Digestion is the physical and chemical breakdown of complex chemicals obtained from eating food. It occurs mostly in the mouth and stomach. Assimilation is the absorption of these simplified, broken down chemical nutrients into the bloodstream for use by the rest of the body. This occurs in the small intestine, in particular the jejunum and ileum. This part of the intestine contains tiny, fiber-like projections called villi that greatly increase the surface area of the intestine to aid in nutrient absorption.