Digestion in the stomach and duodenum Lecture

Digestion in the stomach and duodenum. Lecture

Enzymes Pepsin p. H=1, 5 -2. Gastricsin - p. H=3, 2 -3, 5. Gelatinaze Rennin Lipase

Functions of HCI 1. Pepsinogen activation. 2. Maintenance of an optimal p. H. 3. Proteins denaturation and swelling. 4. Bacteriostatic effect. 5. Regulation of gastric empting. 6. Stimulation of gastrin production by G-cells. 7. Duodenal enterokinase activation.

Functions of the stomach 1. Reservoir. 2. Secretory. 3. Motor. a) Mixing of food with gastric juice until it form a semi fluid mixture called chyme; b) Emptying of food from the stomach into the small intestine. 4. Absorption 5. Defensive 6. Regulatory. 7. Hemopoietic. 8. Excretory.

Types of motility 1. Hunger contraction. 2. Receptive relaxation. 3. Peristalsis (propulsive, antral systole, retropulsion). 4. Antyperistalsis. 5. Gastric emptying.

Phases of gastric secretion 1. Cephalic conditioned unconditioned 2. Gastric 3. Intestinal

Composition of the pancreatic juice ØNon-organic substances Fwater, Fbicarbonates, FNa+, K+, Ca 2+, FCL-, HCO 3 - HPO 42ØOrganic substances (enzymes).

Pancreatic enzymes &Proteases: &trypsinogen; chymotrypsinogen; procarboxypeptidase; proelastase. &Lipase &Carbohydrases: amylase, maltase, lactase. &Nucleases: act on nucleic acids.

Functions of the liver 1. Detoxification of blood 2. The central organ of proteins, fats, carbohydrates metabolism. 3. Storage. 4. Synthesis of plasma proteins, fibrinogen, prothrombin. 5. Digestive functions.

Composition of bile • Non-organic substances – (water, electrolytes, bile salts). • Organic substances: • cholesterol, lecithin, lysozym, bile acids (taurocholic, glycocholic), bile pigments (bilirubin, biliverdin), mucin (bile of gall- bladder). • stercobilin, urobilin.

Functions of bile 1. Emulsification of fats. 2. Absorption of fats. It forms chemical soluble complexes micells. 3. Activates the pancreatic lipase and other enzymes and increases the hepatic and pancreatic secretion. 4. Stimulates intestinal movements (peristalsis). 5. Neutralization of acid in the duodenum. 6. Bactericidal effect.

Intestinal glands: ØBrunner’s glands ØLieberkuhn glands

The daily secretion is 2, 5 l. p. H is 7, 2 -7, 5 (8, 6).

Intestinal juice It contains Ømucus, Øepithelial cells, Ø 22 enzymes (aminopeptidase, enterokinase, lipase, amylase, maltase, lactase for milk sugar, sucrase for sucrose, invertase for cane-sugar, etc. ).

Types of digestion in small intestine. 1. Cavital (in cavity of intestine without direct contact with the mucosa) 2. Membranous

Significance of the membrane digestion 1. Microvillis increase surface square of small intestine. 200 m 2. 2. This process is much faster. 3. After digestion absorption occurs immediately.

Motor function of the small intestine 1. 2. 3. 4. Peristalsis Pendular movements Rhythmical segmentation Contraction of villi.

Functions of bacterial flora (microflora) 1. Carbohydrate fermentation with production of CO 2, H 2 O, CH 4. 2. Protein decay with production of toxic products (indole, skatole, phenol). Toxic products are detoxified in the liver. 3. Breakdown of cellulose. 4. Synthesis of vitamins K and B. 5. Defensive function (inhibition of pathogenic microorganisms). 6. Inactivation of enzymes.

Absorption ØActive transport. Products of hydrolysis of proteins, fats, carbohydrates, ions of Ca, Mg, Fe, Na. ØPassive transport. Water, vitamin C, CI-.

Methods of studying secretory function: 1. Simple fistula of the stomach by Basov. 2. Experiment of sham feeding (esophagotomy) by Pavlov. 3. Isolated miniature stomach or pouch by Klemensiewicz-Heidenhain. The LP = 30 -50 min. 4. Isolated miniature stomach or pouch by Pavlov. The LP=5 -10 min. 5. The radiopill. 6. Probing or sounding (a rubber tube). 7. Endoscopy. X-ray examination.

Methods of studying motor function Ø Gastrography Ø Electrogastrography