Resorption of unconjugated bile salts. Bile that was released and not used in emulsification of lipids are reabsorbed in the ileum. Also known as the enterohepatic circulation.
Secretion of immunoglobulins. IgA from plasma cells in the mucosa are absorbed through receptor mediated endocytosis on the basolateral surface and released as a receptor-IgA complex into the intestinal lumen. The receptor component confers additional stability to the molecule.
Lactose intolerance is the most common problem of carbohydrate digestion and occurs when the human body doesn't produce a sufficient amount of lactase (a disaccharidase) enzyme to break down the sugar lactose found in dairy. As a result of this deficiency, undigested lactose is not absorbed and is instead passed on to the colon. There bacteria metabolize the lactose and in doing so release gas and metabolic products that enhance colonic motility. This causes gas and other uncomfortable symptoms.