DIGESYION IN INTESTINES

Role of pancreas in the digestive system There are two secretor functions of pancreas – external and internal. The external secretor function of pancreas means that exsogenic cells of pancreas and ducts cells produce pancreatic juice. It helps to hydrolyzed protein to peptides and amino acids, carbohydrates to monosaccharides, lipids to the fat acids and glycerin. It neutralizes acidic chymus, which come from stomach. Internal secretor function of pancreas is production of hormones (insulin, glucagons, somatostatin).

Composition and properties of pancreatic juice Quantity of pancreatic juice per day is 1,5-2,0 L. Reaction of it – pH = 8,0-8,5. It consists of a big quantity of hydro carbonates. It has near 10 % of protein – enzymes, which are act on protein, lipids and carbohydrates. According to that there are 3 groups of enzymes: proteolytic lipolytic amilolytic

Proteolytic enzymes Proteolytic enzymes secreted in the inactive enzymatically form. The more important of them are trypsinogen, chymotrypsinogen, and procarboxypolypeptidase. Trypsinogen activated by enzymes enterokinase (produces by the mucous cells of duodenum). After activation tripsinogen has name – tripsin. This enzyme is very active. It also activates chemotripsinogen to form chemotripsin, and procarboxypolypeptidase is activated to the form carboxypolypeptidase in a similar manner. In pancreatic juice presents proteolytic enzymes – elastases, nucleases etc. They hydrolyzed protein to peptides and aminoacids.

Lipolytic and amylolytic enzymes  The main enzymes for fat digestion (lipolytic enzymes) are pancreatic lipase, which is capable of hydrolyzing neutral fat into fatty acids and monoglycerides; cholesterol esterase, which causes hydrolysis of cholesterol esters; and phospholipase, which splits fatty acids from phospholipids. Lipolytic enzymes ejected in active (pancreatic lipase, muntinase) and inactive conditions (prophospholipase A). The pancreatic digestive enzyme for carbohydrates (amilolytic enzyme) is alpha-amylase, which hydrolyzes starches, glykogen, and most other carbohydrates (except cellulose) to form disaccharides and a few trisaccharides.

Regulation of pancreas secretion  There are 3 phases of pancreatic secretion: cephalic, stomach and intestine. The 1 stage caused by nervous influences. N. vagus realizes this effect by helps of conditioned and unconditioned reflexes. Secretion begins after 1-2 minutes of food. Juice consists of enzymes, small quantity of water and ions. Sympathetic influences have a trophy role. During the 2 phase there are two kinds of influences: nervous and humoral (gastrin from stomach). The 3 phase caused by chyme contents. The main is humoral factors (secretin, cholecystokinin-pancreasemin).

Secretin stimulates production of a big quantity of juice with a high concentration of hydrocarbonates and a small quantity of enzymes in ducts cells. CKP stimulates production of a less quantity of juice with a big concentration of enzymes in acinars cells. Secretion of pancreatic juice stimulates also by vaso-intestinal polypeptide, serotonine, insulin, bombesin, sustantio P calcium ions, and salts of bile acids. Secretion of pancreatic juice inhibits by glukagon, calcitonin, somatostatin. During dreams, hart physical and mental activity, pain secretion inhibits too.

Bile production and bile secretoin Secretion of bile occur all time and increase by influences of bile acids, cholecystokinin-pancreasemin, secretin. Bile secretion in the duodenum depends from take food (minerals water, HCl, fatty acids increase bile formation). It depends of nervus vagus (increase bile formation) and humoral influences – concentration of cholecystokinin-pancreasemin (increase bile formation and ejection), secretin, gastrin.

Composition of bile: bilirubin, bile acids, cholesterol, leukocytes, some epitheliocytes, cristalls of bilirubin, calcium.

The role of bile 1. Neutrolyze the stomach acid; 2. Inhibit the act of stomach proteases; 3. Increase the activity of pancreatic lipase; 4. Emulsificates the lipids by help of bile acids actions; 5. Bile acids help stabilizing of emulsion; 6. Increase the absorption of fatty acids, carrotin, vitamins K, D, E; 7. Increase tone and motor function of intestines (more duodenum and large intestine); 8. Decrease the activity of intestine micro flora; 9. Take place of enzymes fixation on the intestines surface.

Composition and properties of intestine juice Composition of intestine juice: mucine, enzymes – peptidase, saccharase, maltase, lactase, lipase, phosphatase, nuclease; immunoglobulins; ions; leukocytes; epitheliocytes (200 g per day).  pH of intestine juice is 7,5-8,0; production per day – near 1,8-2,5 L.  Functions: ending hydrolyses of all nutritive substances; protective of mucus wall; support of chyme in fluid condition; formed of base reaction of intestine contents. Increase secretion: parasympathetic nerves, secretine, and glucagons.

Digestion in the large intestine Composition of intestine juice: mucus, epithelial cells, and small quantity of enzymes (peptidase, lipase, nuclease, phosphatase).   Functions: protective from mechanical, chemical irritations; formed of base reaction of intestine contents. 

Role of the micro flora of large intestine 1. Ending decompose of all nutritive substances, which are do not digested in small intestines. 2. Synthesis of some vitamins – of B group, vitamin K. 3. Take place in metabolic processes. 4. Stimulates absorption of water and amino acids. 5. Inactivate enzymes of small intestines. 6. Forms normal reaction in large intestine. 7. Decompose organic substances of chyme. 8. Have protective role to the pathogenic microorganisms.