DIGESTION

ABSORPTION The taking in of substances thru cell membrane or layers of cells The taking in of substances thru cell membrane or layers of cells Movement is from lumen of gut into blood or lymph capillaries Movement is from lumen of gut into blood or lymph capillaries

ASSIMILATION Conversion of nutrients into fluids or solids for use by the organism Conversion of nutrients into fluids or solids for use by the organism Occurs only after absorption Occurs only after absorption

STOMACH  Stores food while waiting to move to small intestine – peristalsis moves food along and determines when more leaves the stomach  Chemical digestion of protein by pepsin into shorter polypeptudes  Pepsinogen is precursor & produced by chief cells in wall

 Pepsinogen activated by HCl produced in parietal cells of wall  HCl produced in wall, causes pH to be 2, & kills ingested pathogens

SMALL INTESTINE DIGESTION DIGESTION A. 2 enzymes sources A. 2 enzymes sources 1. wall of sm. Intestine 1. wall of sm. Intestine 2. exocrine cells of pancreas 2. exocrine cells of pancreas B. Bile from liver secreted into sm. Intes. B. Bile from liver secreted into sm. Intes. 1. Contains salts that emulsify fats 1. Contains salts that emulsify fats so lipase has larger surface area so lipase has larger surface area 2. Bile is NOT an enzyme 2. Bile is NOT an enzyme

ABSORPTION occurs thru villi & microvilli ABSORPTION occurs thru villi & microvilli Glucose is primary absorbed material Glucose is primary absorbed material More products of digestion can be absorbed at same time due to structure of villi & microvilli More products of digestion can be absorbed at same time due to structure of villi & microvilli 1. Small carbs like glucose & amino acids go to blood & to liver 1. Small carbs like glucose & amino acids go to blood & to liver 2. Lipids absorbed by lacteals go to lymph system 2. Lipids absorbed by lacteals go to lymph system

3. Absorbed fat is transported to lymph to drain into circulatory system at subclavian vein 3. Absorbed fat is transported to lymph to drain into circulatory system at subclavian vein 4. Absorbed products must be moved rapidly in order to maintain concentration gradient which helps the absorption process 4. Absorbed products must be moved rapidly in order to maintain concentration gradient which helps the absorption process

LARGE INTESTINE 1. Absorption of water 1. Absorption of water 2. Absorption of minerals 2. Absorption of minerals BOTH OCCUR BY OSMOSIS BOTH OCCUR BY OSMOSIS

LIVER FUNCTIONS I. Regulates nutrient levels in blood 1. stores glucose for later use 1. stores glucose for later use 2. stored as glycogen under influence of insulin ( hormone produced by β cells of Islets of Langerhans in pancreas 2. stored as glycogen under influence of insulin ( hormone produced by β cells of Islets of Langerhans in pancreas 3. glucagon (hormone from α cells) converts glycogen to glucose 3. glucagon (hormone from α cells) converts glycogen to glucose 4. proteins broken down by proteases 4. proteins broken down by proteases

& de-amination & trans-amination for building proteins releases energy & de-amination & trans-amination for building proteins releases energy II. STORES NUTRIENTS 2. Carbohydrates 2. Carbohydrates 3. Iron 3. Iron 4. Vitamins A & D 4. Vitamins A & D III. SYNTHESIZES PLASMA PROTEINS & CHOLESTEROL

1. Fibrinogen, globulins like gamma- globulin (antibody) 1. Fibrinogen, globulins like gamma- globulin (antibody) 2. Maintains correct concentrations of plasma proteins & water in blood & interstitial fluid – important to hydrostatic pressure & osmosis 2. Maintains correct concentrations of plasma proteins & water in blood & interstitial fluid – important to hydrostatic pressure & osmosis IV. DETOXIFICATION 1. Pesticides, medicine, & alcohol 1. Pesticides, medicine, & alcohol

V. PHAGOCYTIC V. PHAGOCYTIC 1. breaks down hemoglobin 1. breaks down hemoglobin 2. breaks down RBC’s along with spleen & red bone marrow 2. breaks down RBC’s along with spleen & red bone marrow