Disorders of the Gastrointestinal Tract, Pancreas, Liver and Gall Bladder

The gastrointestinal tract (GIT) is essentially a long tube extending from the mouth to the anus with a number of specialized regions. Most of the nutrients (Chapter 10) in food have to be digested before they can be assimilated. Digestion involves the hydrolysis of polysaccharides, oligosaccharides, proteins and lipids in enzyme-catalyzed reactions. The products of hydrolysis, such as monosaccharides, amino acids, free fatty acids and monoacylglycerols, can then be absorbed. Some nutrients, vitamins and minerals for instance, are absorbed without the need for digestion. The digestion of food and absorption of the released nutrients are the major functions of the GIT together with its accessory organs, the pancreas, liver and gall bladder. The peritoneum lines the abdominal cavity and covers the major organs. Folds of the peritoneum, called the mesentery, and mesocolon hold the intestines in place. The GIT has significant roles in the homeostasis of nutrients and in protecting the body against pathogens (Chapter 2) ingested with the food. Digestion and absorption, can, of course, only take place after ingestion of food, unlike the homeostatic and protective functions that operate continuously. OBJECTIVES After studying this chapter you should be able to: