Secretion of digestive juices Introduction to alimentary glands Saliva Gastric secretions Pancreatic secretions Bile (Biochemistry) Secretions of small intestine Secretions of large intestine

Secretion of digestive juices Introduction to alimentary glands Saliva Gastric secretions Pancreatic secretions Bile Secretions of small intestine Secretions of large intestine

Secretions of small intestine

Small intestine absorptive surface 1 cm Valvulae Conniventis 1 mm 1μm

Villi projecting from small intestine mucosa

A single villus

Mucous membrane on small intestine (Numerous villi on a circular fold)

Secretion of mucus in Duodenum Brunner’s Glands (Duodenal glands) Compound mucus glands First few cm of duodenum (Duodenal cap or bulb) Alkaline Stimulus: Tactile Irritation Vagal stimulation Secretin Inhibited by Sympathetic stimulation → unprotected → ulcer

Functions of mucus secreted by Brunner’s glands Protect the duodenal wall from highly acidic gastric juice It contains Bicarbonate Neutralize acid pH of stomach Optimum pH for pancreatic enzymes Blockage of digestive action of digestive enzymes of stomach (because digestive enzymes of stomach become inactivated at pH>3-4.5 Holds immunoglobulins in place

Characteristics of secretions of small intestine Enterocytes covering the villi contain enzymes Digestion during absorption For digestion of proteins Peptidases For digestion of carbohydrates Sucrase, maltase, isomaltase, lactase For digestion of fats Intestinal lipase Ph= 7.5-8 1800 ml/day Composition Water (For Hydrolysis, for digestion) Mucus Electrolytes Na, Cl, HCO3 Enzymes No enzymes

Question 3 sources of Mucus in small intestine Surface epithelial cells Brunners glands Goblet cells

Regulation of small intestinal secretions Local enteric nervous reflexes Tactile stimuli Irritative stimuli

Disorders of small intestine Peptic ulcer Malabsorption Diarrhea

Peptic Ulcer Gastric Ulcer Duodenal Ulcer Definition: An excoriated area of stomach or intestine principally caused by the digestive action of gastric juice or upper small intestine Frequent site: within few cm of Pylorus

Causes of Peptic Ulcer Imbalance between Rate of secretion of gastric juice Degree of protection by Gastroduodenal mucosal barrier Neutralization of gastric acid by duodenal juices Pancreatic secretions Bile

H. Pylori appear on silver staining as small, curved rods on the surface of Gastric mucosa

H. Pylori

Predisposing factors of Gastric Ulceration Psychic disturbances (↑ acid secretion) Smoking ( Nervous stimulation of gastric secretions) Alcohol ( Break down the Mucosal Barrier) Aspirin etc. ( Break down the Mucosal Barrier)

Physiology of Treatment of Peptic Ulcer Antibiotics Acid-suppressant drugs Antacids Treat and remove the cause Surgical

Complications of Peptic Ulcer Stricture Perforation Bleeding Treatment: Surgical

Malabsorption Damage to < 50% of small intestine Intestinal adaptation Hypertrophy and hyperplasia Damage to > 50% of small intestine Malabsorption

MCQ: Peptic ulceration tends to heal after all of the following EXCEPT: A. Aspirin therapy B. Division of the vagal nerve supply to the stomach C. Proton pump inhibitors D. Surgical removal of the pyloric antrum E. Treatment with histamine H2 blocking drugs A

MCQ: Intestinal secretions contain enzymes which A. activate pancreatic proteolytic enzymes B. are released when the vagus nerve is stimulated C. digest cellulose D. hydrolyze disaccharides E. hydrolyze monosaccharides A

A. acting as a protective barrier for intestinal epithelium MCQ: The intestinal brush border promotes digestion by all of the following mechanisms EXCEPT: A. acting as a protective barrier for intestinal epithelium B. facilitating movement of intestinal contents C. increasing the surface area of intestinal mucosa D. supplying digestive enzymes E. supplying specialized transport system B

MCQ: With regards to secretions of small intestine A. Daily secretion is about 800 ml/day B. Sodium is added to secretions ay active transport C. Epithelial cells in villi secrete water and electrolytes D. Digestive enzymes are mainly intracellular E. ph is about 6.5 -7 D

MCQ: Crypts of Lieberkϋhan A. Are complex glands present throughout small intestine B. Are present throughout small and large intestine except duodenum C. Are separated by villi D. Contain both Goblet cells and enterocytes E. Secrete digestive enzymes for final digestion of food D