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Fig. 41-7 Digestion, Absorption, Excretion Small molecules Today’s topics: • Digestive System Pieces of food Mechanical digestion Hydrolysis • Stomach, Liver, Pancreas Chemical digestion Nutrient (enzymatic hydrolysis) molecules enter body cells Undigested material Food Absorption • Intestine 1 Ingestion • Excretion • Kidney (if time) 2 Digestion 3 Absorption 4 Elimination 6 April 2009 Fig. 41-UN1 Fig. 41-8 Bloodstream Tentacles Veins to heart Lymphatic system Gastrovascular cavity Food Hepatic portal vein Mouth Liver Mouth Lipids Stomach Absorbed food Absorbed (except lipids) water Esophagus Small intestine Secretions from the gastric glands of the stomach Anus Large Rectum intestine Epidermis Secretions from the pancreas and the liver Gastrodermis Fig. 41-12b Digestive System Interior surface of stomach Epithelium 3 Pepsinogen Mucus cells Gallbladder 1 Pepsinogen and HCl are secreted. 2 HCl converts 1 Stomach Ascending portion of large intestine Pepsin HCl Gastric gland Liver 2 Cl– pepsinogen to pepsin. H+ 3 Pepsin activates more pepsinogen. Pancreas Chief cells Small intestine Small intestine Large intestine Chief cell Parietal cells Parietal cell Appendix Cecum 1 Fig. 41-13 Carbohydrate digestion Oral cavity, pharynx, esophagus Protein digestion Nucleic acid digestion Fat digestion Polysaccharides Disaccharides (starch, glycogen) (sucrose, lactose) Salivary amylase Liver Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of Polysaccharides small intestine Stomach DNA, RNA Polypeptides Pancreatic amylases Pancreatic trypsin and chymotrypsin Fat globules Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets Nucleotides Smaller polypeptides Small peptides Disaccharidases Nucleotidases Dipeptidases, carboxypeptidase, and aminopeptidase Monosaccharides Gallbladder Glycerol, fatty acids, monoglycerides Amino acids Epithelium of small intestine (brush border) Spleen Pancreatic lipase Pancreatic carboxypeptidase Kidney Nucleosides Nucleosidases and phosphatases Pancreas Nitrogenous bases, sugars, phosphates Amino acids Duodenum Fig. 41-10a Intestinal villi and brush border increase surface area for absorption Ascending portion of large intestine Intestine Small intestine Appendix Cecum http://www.vanderbilt.edu/exploration/text/index.php?action=view_section&id=1268&story_id=304&images= Absorption Absorption Vein carrying blood to hepatic portal vein Villi Brush Border Brush border Blood capillaries Epithelial cells Epithelial cells Villi Lacteal Key Nutrient absorption Lacteal Epithelial cells Intestinal wall Capillaries Lymph vessel Villi Lymph vessel Key Nutrient absorption Fig. 41-15 Fig. 41-15b 2 Back to the Liver Maintaining Glucose Balance • Hepatic vein takes absorbed nutrients to liver Stimulus: Blood glucose level rises after eating. – Adjust nutrient balance – De-tox poisons Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level drops below set point. Liver is a major protein synthesis site Fig. 41-21 Fig. 41-20 1 Colon Rumen 2 Reticulum Intestine Esophagus Small intestine Small intestine Stomach Cecum Colon (large intestine) Carnivore Fig. 41-19 4 Herbivore Stomach 3 Omasum Filtration Capillary Filtrate Kidney is a blood filter Liver Abomasum Excretory tubule Reabsorption Spleen Gallbladder Secretion Kidney Urine Pancreas Excretion Duodenum Fig. 44-10 3 Fig. 44-14d Kidney uses osmosis to concentrate urine Glomerulus Bowman’s capsule Proximal tubule NaCl Nutrients HCO3– H2 O K+ H+ NH3 Distal tubule H2 O NaCl K+ HCO3– H+ Filtrate CORTEX Loop of Henle NaCl OUTER MEDULLA Collecting duct H2 O NaCl Collecting duct Key Loop of Henle Active transport Passive transport Urea NaCl H2 O INNER MEDULLA Fig. 44-15 Kidney uses osmosis to concentrate urine Osmolarity of interstitial fluid (mOsm/L) 300 300 100 300 100 CORTEX H2 O H2 O 400 NaCl 300 300 400 400 H2 O NaCl 200 H2 O NaCl H2 O NaCl H2 O NaCl H2 O NaCl OUTER MEDULLA 600 H2 O H2 O Key Active transport Passive transport INNER MEDULLA H2 O 400 NaCl 900 NaCl NaCl H2 O 600 600 H2 O Urea 700 H2 O Urea 900 H2 O Urea 1,200 1,200 1,200 4
