POWERPOINT ® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin Additional Text by J Padilla exclusively for Physiolgy at ECC Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings HUMAN PHYSIOLOGY AN INTEGRATED APPROACH FOURTH EDITION DEE UNGLAUB SILVERTHORN UNIT 4 PART A 21 The Digestive System

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Basic Processes of the Digestive System Figure 21-1 Ingestion Mechanical Digestion Chemical Digestion Absorption Defication Peristalsis (motility) Secretion Ingestion Mechanical Digestion Chemical Digestion Absorption Defication Peristalsis (motility) Secretion

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Digestion and Absorption A villus and a crypt in the small intestine- stem cells in crypt helps to replace the stomach lining. Crypts are used for peptide absorption in newborns.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Carbohydrate Digestion American diets are rich in starch and sucrose. Can only absorb monsacchirdes. Cellulose is not digestable (fiber).

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Carbohydrate Absorption in the Small Intestine Glucose & galactose move via transporter and depend on ion movemnt. Intestinal cells use glutamate as an energy source to not consume glucose.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Enzymes for Protein Digestion Endopeptidases (proteases) break down polypeptides to smaller peptide fragments that are then broken down by exopeptidases in amino acids. Endopeptidases are usually released in an inactive form (proenzymes) that once activated have a different name: pepsin, trypsin, and chymotrypsin. *egg protein is the easiest to digest and absorb Endopeptidases (proteases) break down polypeptides to smaller peptide fragments that are then broken down by exopeptidases in amino acids. Endopeptidases are usually released in an inactive form (proenzymes) that once activated have a different name: pepsin, trypsin, and chymotrypsin. *egg protein is the easiest to digest and absorb

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Peptide Absorption Amino acids and small peptides cross the cell through transporter proteins. Larger peptides are endocytosed. Permeability of peptides increases in pregnant and nursing women and in newborns.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Digestion and Absorption Triglycerides digest into monoglycerides and free fatty acids – lipases free the fatty acid chains, phospholipase digest glycerol, and free cholesterol is not digested.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Digestion and Absorption of Fats Capillary Cells of small intestine Interstitial fluid Triglycerides + cholesterol + protein Lymph to vena cava Lacteal Golgi apparatus Smooth ER Chylomicron Lumen of small intestine Large fat droplets from stomach Lipase and colipase Emulsion Bile salts recycled Micelles Bile salts from liver Monoglycerides and fatty acids move out of micelles and enter cells by diffusion. Pancreatic lipase and colipase break down fats into monoglycerides and fatty acids stored in micelles. Chylomicrons are released into the lymphatic system. Absorbed fats combine with cholesterol and proteins in the intestinal cells to form chylomicrons. Bile salts from liver coat fat droplets. Cholesterol is transported into cells by a membrane transporter a 3b a 3b 4 5 Bile salts break down large fat droplets are to increase surface area for digestion. This forms an emulsion in which colipase is needed for lipase to digest the fat and form micelles. Fat diffuses in and cholesterol is moved by a transporter. Chylomicrons form inside cells and move into lacteals. Some smaller fatty acids move into capillaries

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-19, steps 1–2 Digestion and Absorption of Fats Capillary Cells of small intestine Interstitial fluid Lumen of small intestine Large fat droplets from stomach Lipase and colipase Emulsion Micelles Bile salts from liver Pancreatic lipase and colipase break down fats into monoglycerides and fatty acids stored in micelles. Bile salts from liver coat fat droplets Lacteal

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-19, steps 1–3a Digestion and Absorption of Fats Capillary Cells of small intestine Interstitial fluid Lumen of small intestine Large fat droplets from stomach Lipase and colipase Emulsion Bile salts recycled Micelles Bile salts from liver Monoglycerides and fatty acids move out of micelles and enter cells by diffusion. Pancreatic lipase and colipase break down fats into monoglycerides and fatty acids stored in micelles. Bile salts from liver coat fat droplets a 1 2 Lacteal

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-19, steps 1–4 Digestion and Absorption of Fats Capillary Cells of small intestine Interstitial fluid Triglycerides + cholesterol + protein Smooth ER Chylomicron Lumen of small intestine Large fat droplets from stomach Lipase and colipase Emulsion Bile salts recycled Micelles Bile salts from liver Monoglycerides and fatty acids move out of micelles and enter cells by diffusion. Pancreatic lipase and colipase break down fats into monoglycerides and fatty acids stored in micelles. Absorbed fats combine with cholesterol and proteins in the intestinal cells to form chylomicrons. Bile salts from liver coat fat droplets. Cholesterol is transported into cells by a membrane transporter a 3b a 3b 4 Lacteal

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-19, steps 1–5 Digestion and Absorption of Fats Capillary Cells of small intestine Interstitial fluid Triglycerides + cholesterol + protein Lymph to vena cava Lacteal Golgi apparatus Smooth ER Chylomicron Lumen of small intestine Large fat droplets from stomach Lipase and colipase Emulsion Bile salts recycled Micelles Bile salts from liver Monoglycerides and fatty acids move out of micelles and enter cells by diffusion. Pancreatic lipase and colipase break down fats into monoglycerides and fatty acids stored in micelles. Chylomicrons are released into the lymphatic system. Absorbed fats combine with cholesterol and proteins in the intestinal cells to form chylomicrons. Bile salts from liver coat fat droplets. Cholesterol is transported into cells by a membrane transporter a 3b a 3b 4 5

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Digestion and Absorption The role of bile salts in emulsions and micelles

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Digestion and Absorption  Nucleic acids are digested into nitrogenous bases and monosaccharides – all components are absorbed by transport mechanisms, they are not considered a calorie source and make up a small % of the diet.  Intestine absorbs vitamins and minerals – some vitamins must be coupled with fats or proteins to be better absorbed.  Fat-soluble absorbed with fats – excessive quantities and cause toxicity. Incorrect fat ingestion can cause vitamin deficiency.  Water-soluble by mediated transport – (C and most B vitamins), can be excreted if there is excess  Vitamin B 12 when complexed to intrinsic factor and absorbed in ileum – found in meats, sea food, and milk products.  Mineral by active transport – Fe and Ca absorption is based on need. Fe is absorbed as heme and Ca absorption is hormone mediated or by passive movement.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Digestion and Absorption NaCl reabsorption in the small intestine and colon Three transporters are used to absorb sodium so water can move in too. Ion movement includes Cl-, H+, K+, andHCO3-