Digestion Absorption metabolism Digestion in mouth digestion body
Digestion , Absorption , & metabolism
Digestion in mouth
-digestion Ø - body food component travel together , through GIT into the cell. Ø *basic principles of digestion: Ø prepares the food for the body use , under effect of muscular &chemical reaction. Ø -muscular layer of the elementary system (serosa, submucosa, &mucosa), &fiber layer longitudinal or circular layer, help in the movement of food &push it forward , this movement called peristalsis. Ø -chyme: fluid secreted by GIT to help in digestion. Ø -the action of food is under control of nervous system at GIT wall called intra-mural nervous plexus extend from esophagus to anus responsible for regulation of the rate &intensity of muscle contraction with coordination in various movement.
Ø definition of digestion: Ø -the process of break down food to release its nutrients for absorption & transport to the cell for use in the body. Ø *peristalsis: Ø Wave like progression of contraction & relaxation. Ø **types of GIT secretion: Ø -1 -Enzymes: chemical action e. g. lipase , amylase. Ø -2 -hydro-choloric acid & buffer ions : necessary ph. Ø -3 -mucous: protect the inside wall tissue of GIT, lubricate &facilitate food mass passage. Ø Ø -4 -water & electrolyte
Ø Mouth& esophagus: preparation &delivery: Ø -1*mastication: Ø -chewing break-down food into smaller particles by teeth & jaw muscle with tongue. Ø -2*swallowing: Ø -occur at mouth & pharynx. Ø -rapid less than one second. Ø -coordination &swallowing comes from(swallowing centre area) in the brain stem. Ø -gravity &muscle at the base of the tongue , help in the movement of the food down to esophagus , in the upright position. Ø -in the stomach food enter by opening of the sphincter to prevent reflux , &occurrence of heart burn.
Ø ** chemical or secretary digestion : 3 pairs of salivary glands , parotid , sub-maxillary , sub-lingual , secrete salivary amylase this enzyme is specific for starch digestion. Ø *factors affect salivary secretion : Ø 1 -sight. 2 -smell. 3 -taste. 4 -touch. 5 -thought of like & dis-like of food. Ø -normal range of daily saliva secretion between 8001500 ML, p. H neutral 6. 0 7. 4
stomach : storage & initial digestive process. Ø --as the food enter the stomach , the muscle of the stomach mix the food , storage , &control emptying. Ø -when the food mixed with chyme , the pyloric sphincter constrict & relax for control of emptying at duodenum. Ø **types of stomach secretion : Ø a-acid : HCL hydro chloric acid. Ø b-mucous : protect the wall of lining stomach & lubricant. Ø c- enzymes: pepsin , break down of protein (pepsinogen converted to pepsin under HCL secretion ), gastric lipase for fat , rennin in child-hood aid in co-agulation of milk , but absent in adult.
Ø -control process of gastric secretion under effect of : Ø 1 -nervous stimulus in response to sense , ingested food & emotions , e. g. anger & hostility increase secretion , while fear & depression , decrease secretion. Ø 2 -hormonal stimulus in response to entrance of food into stomach , e. g. gastric enterogastrone.
Ø -control process of gastric secretion under effect of : Ø 1 -nervous stimulus in response to sense , ingested food & emotions , e. g. anger & hostility increase secretion , while fear & depression , decrease secretion. Ø 2 -hormonal stimulus in response to entrance of food into stomach , e. g. gastric enterogastrone.
Problems related to food digestion Incomplete digestion Lack of digestive enzymes Gallstones
Absorption Ø Ø Ø -end product of digestion. -CHO (glucose, fructose, galactose ). -fat (fatty acid , glycerides). -protein (amino-acid ). -villi: finger like projection seen under microscope help in absorption.
Ø *Routes Ø Ø Ø of absorption : -proteins &CHO become water soluble , enter to blood stream , go to liver , &other tissue , while fat is not water soluble , bile secreted in intestine , help in digestion of fat. Large intestine : final absorption & waste elimination. Water absorption take side at colon. As much as 25% of meal may remain in rectum up to 7 hrs. Mineral absorption : Essential minerals as Na & K go to blood stream.
Ø Ø Ø Bacteria in the colon syntheses vit K. -intestinal bacteria affect color & odor of the stool. Brown stool comes from bile pigment. Intestinal gas or flatus produced by bacteria. Fiber does not digested so it contribute to form bulk of the stool. Ø Normal feces contain 75% water, 25% solids. Ø Solids ( fiber , bacteria , minerals , small amount of fat , mucous).
Villus epithelium epithelial cells Capillary network lacteal Villi – plural of villus
Ø Metabolism Ø 1 -CHO metabolism : Ø Source of blood glucose *CHO &non CHO substances * Ø *CHO sources: Ø -dietary starch & sugars. Ø -glycogen from liver & muscle tissue , by hydrolysis glycogen to glucose. Ø *non CHO sources: Ø -from protein & fat.
Ø -indirect source of glucose. Ø *in case of protein glycogenic amino-acid could be used in energy , if insufficient CHO. Ø *in case of fat broken to fatty acid &glycerol , glycerol converted to glycogen in the liver. Ø -the process of production of glucose from protein or fat is called gluconeogenesis.
Ø -normal Ø Ø Ø blood glucose level 70 -120 mg dl. 1 - energy production. 2 -energy storage : Glucose converted to glycogen , stored in liver 7 muscle tissue. Excess glucose converted to fat & stored in adipose tissue (fat tissue ). 3 - glucose product : Glucose enter in DNA &RNA building.
Ø **hormonal controls : Ø -blood sugar lowering hormones Ø a- insulin decrease blood sugar , produced by beta cells in the pancreas. Ø -convert glucose in the liver to glycogen by process called glycogen sis. Ø -convert glucose to fat & storage in adipose tissue
Ø b-blood sugar raising hormones : Ø *1 -glycogen -produced from alpha cells of pancreas, opposite action of insulin. Ø *2 -somatostatin: Ø -delta cells of pancreas. Ø -anti insulin effect Ø. Ø *3 -steroid hormones : Ø -secreted from adrenal gland. Ø -anti insulin effect.
Ø Ø Ø Ø *4 -Epinephrine : -secreted from adrenal medulla. -break down glycogen in the liver to glucose. *5 -grouth hormone : -secreted from anterior pituitary gland. -anti insulin effect. *6 -thyroxine : -increase glucose absorption from intestine
Ø -2 -lipid metabolism : Ø *liver &muscle responsible for fat production& fat breakdown. Ø *lipo-protein comes from absorption of protein &fat from intestine. Ø *GH, ACTH, TSH increase release of fatty acid / Ø *cortisone & hydro-cortisone increase fatty acid production. Ø *Epinephrine , non epinephrine , thyroxin , insulin * decrease cholesterol secretion. Ø-
Ø 3 -protein metabolism Ø : -responsible about tissue building , &tissue break down. Ø -GH, gonadotrophine hormone , thyroxin participate in tissue anabolism tissue catabolism. Ø -break down of protein give amino acid. Ø -amino acid divided to : Ø *1 nitrogen , end product is ammonia passed in urine & stool. Ø *2 non nitrogen residue (ketoacid). Ø *3 control agent (co-enzymes), enter in metabolic process.
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