tailieunhanh - Ebook Gastrointestinal physiology (8th edition): Part 2

(BQ) Part 2 book "Gastrointestinal physiology" presents the following contents: Gastric secretion, pancreatic secretion, bile secretion and gallbladder function, digestion and absorption of nutrients, fluid and electrolyte absorption, regulation of food intake. | GASTRIC SECRETION OBJ ECTIVES Identify the secretory products of the stomach their cells of origin and their functions. Understand the mechanisms making it possible for the stomach to secrete 150 mN hydrochloric acid. Describe the electrolyte composition of gastric secretion and how it varies with the rate of secretion. Identify the major stimulants of the parietal cell and explain their interactions. Discuss the phases involved in the stimulation of gastric acid secretion and the processes acting in each. Identify factors that both stimulate and inhibit the release of the hormone gastrin. Explain the processes that result in the inhibition of gastric acid secretion following the ingestion of a meal and its emptying from the stomach. Describe the processes resulting in gastric and duodenal ulcer diseases. F ive constituents of gastric juice intrinsic factor hydrogen ion H pepsin mucus and water have physiologic functions. They are secreted by the various cells present within the gastric mucosa. The only indispensable ingredient in gastric juice is intrinsic factor required for the absorption of vitamin B12 by the ileal mucosa. Acid is necessary for the conversion of inactive pepsinogen to the enzyme pepsin. Acid and pepsin begin the digestion of protein but in their absence pancreatic enzymes hydrolyze all ingested protein so no nitrogen is wasted in the stools. Acid also kills a large number of bacteria that enter the stomach thereby reducing the number of organisms reaching 64 the intestine. In cases of severely reduced or absent acid secretion the incidence of intestinal infections is greater. Mucus lines the wall of the stomach and protects it from damage. Mucus acts primarily as a lubricant protecting the mucosa from physical injury. Together with bicarbonate HCO3- mucus neutralizes acid and maintains the surface of the mucosa at a pH near neutrality. This is part of the gastric mucosal barrier that protects the stomach from acid and pepsin digestion. Water .