The gastrointestinal (GI) tract regulates the digestion and absorption of water and nutrients, including vitamins, proteins, carbohydrates, and fats, and allows for their uptake into the circulation and use for energy-requiring functions. The mucosa of the GI tract is the largest organ in the body, and is the largest surface area that is exposed to the external environment. This large surface area allows for efficient uptake of nutrients, but also exposes the body to potential toxins and pathogens and thereby presents challenges for the immune system. This chapter reviews the relationships between gastrointestinal physiology and function in health and disease. 2008 Copyright 2008 Elsevier Inc. All rights reserved.
