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Human Digestion

Human Digestion. Human digestion (General plan). Organs of the GI tract. Accessory digestive organs. Chemical digestion is aided by enzymes. Protein digestion. Fat digestion. Nucleic acid digestion. Carbohydrate digestion. Oral cavity, pharynx, esophagus. Polysaccharides

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Human Digestion

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  1. Human Digestion

  2. Human digestion (General plan) Organs of the GI tract Accessory digestive organs

  3. Chemical digestion is aided by enzymes

  4. Protein digestion Fat digestion Nucleic acid digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Fat globules (Insoluble in water, fats aggregate as globules.) Polypeptides Polysaccharides DNA, RNA Pancreatic amylases Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Small peptides Epithelium of small intestine (brush border) Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Disaccharidases Nucleosidases and phosphatases Monosaccharides Nitrogenous bases, sugars, phosphates Amino acids Chemical digestion Chewing, peristalsis Churning, mixing Peristalsis, mixing Large intestine Resident bacteria in the colon digest material in chyme. Vitamin-K and some B-complex vitamins are released by these bacteria.

  5. Composition of the adult human body

  6. Protein digestion Fat digestion Nucleic acid digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Fat globules (Insoluble in water, fats aggregate as globules.) Polypeptides Polysaccharides DNA, RNA Pancreatic amylases Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Small peptides Epithelium of small intestine (brush border) Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Disaccharidases Nucleosidases and phosphatases Monosaccharides Nitrogenous bases, sugars, phosphates Amino acids Chemical digestion Chewing, peristalsis Churning, mixing Peristalsis, mixing Large intestine Resident bacteria in the colon digest material in chyme. Vitamin-K and some B-complex vitamins are released by these bacteria.

  7. Digestion in the Mouth Salivary glands • Produce saliva • Mostly water • Some enzymes • Salivary amylase • Lysozyme • Mucus or mucin

  8. Digestion in the Mouth • Teeth • Mechanical digestion • Different teeth • Different functions • Fit omnivore diet • Tongue

  9. Swallowing: from mouth to stomach

  10. Protein digestion Fat digestion Nucleic acid digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Fat globules (Insoluble in water, fats aggregate as globules.) Polypeptides Polysaccharides DNA, RNA Pancreatic amylases Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Small peptides Epithelium of small intestine (brush border) Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Disaccharidases Nucleosidases and phosphatases Monosaccharides Nitrogenous bases, sugars, phosphates Amino acids Chemical digestion Chewing, peristalsis Churning, mixing Peristalsis, mixing Large intestine Resident bacteria in the colon digest material in chyme. Vitamin-K and some B-complex vitamins are released by these bacteria.

  11. Stomach • Muscular sac • Churns & mixes food • Gastric glands • Parietal cells  HCl, intrinsic factor • Goblet cells  mucus • Chief cells  pepsinogen, weak gastric lipase • Gastrin • Hormone • Controls gastric juices • Comes out as chyme (2-6 hours)

  12. Structure of Stomach

  13. Stomach Esophagus Cardiac orifice Folds of epithelial tissue Pyloric sphincter Small intestine 5 µm Interior surface of stomach. - Highly folded - Dotted with pits 2 3 1 1 2 3 Pepsinogen and HCI secreted into lumen Epithelium HCl converts pepsinogen to pepsin Pepsinogen Pepsin (active enzyme) • Gastric gland. • Secrete gastric juice • Three types of cells HCl Pepsin activates more pepsinogen Mucus cells Chief cells - Pepsinogen Parietal cell Chief cell Parietal cells - Secrete HCl Stomach: Storage and continuation of chemical digestion

  14. Liver • Secretes bile (stored in gall bladder) • Components: Bile salts & bile pigments • Emulsifies fats Gallbladder • Stores, concentrates, and releases bile into duodenum • Cystic duct + hepatic duct = common bile duct • Stimulated by the hormone cholecystokinin (CCK)

  15. Pancreas • Exocrine function • Acinar cells secrete pancreatic juice • Amylase • Lipase • Trypsin • Chymotrypsin • Carboxypeptidase • Nuclease • NaHCO3- • Secretin and cholecystokinin (CCK)fr intestinal wall stimulates PJ production

  16. Pancreas: enzyme production

  17. Protein digestion Fat digestion Nucleic acid digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Fat globules (Insoluble in water, fats aggregate as globules.) Polypeptides Polysaccharides DNA, RNA Pancreatic amylases Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Small peptides Epithelium of small intestine (brush border) Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Disaccharidases Nucleosidases and phosphatases Monosaccharides Nitrogenous bases, sugars, phosphates Amino acids Chemical digestion Chewing, peristalsis Churning, mixing Peristalsis, mixing Enteropeptidase Large intestine Resident bacteria in the colon digest material in chyme. Vitamin-K and some B-complex vitamins are released by these bacteria.

  18. Small Intestine – 6m • Completes digestion of nutrients in chyme • Absorbs products of digestion • Receives enzymes from pancreas and gall bladder • Lumen, villi, lacteal, microvilli, intestinal glands • Watery fluid, digestive enzymes on microvilli: disaccharidase, dipeptidase, nucleotidases 25 cm 1-2 m 2 m

  19. Liver Stomach Bile Gall-bladder Acid chyme Intestinaljuice Pancreas Pancreatic juice Duodenum of small intestine Small intestine: Main organ of digestion and absorption

  20. Digestion of polypeptides lipids and nucleic acids in the duodenum

  21. Protein digestion Fat digestion Nucleic acid digestion Carbohydrate digestion Oral cavity, pharynx, esophagus Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intes- tine Fat globules (Insoluble in water, fats aggregate as globules.) Polypeptides Polysaccharides DNA, RNA Pancreatic amylases Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Pancreatic nucleases Bile salts Maltose and other disaccharides Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Nucleotides Smaller polypeptides Pancreatic carboxypeptidase Pancreatic lipase Amino acids Glycerol, fatty acids, glycerides Small peptides Epithelium of small intestine (brush border) Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Disaccharidases Nucleosidases and phosphatases Monosaccharides Nitrogenous bases, sugars, phosphates Amino acids Chemical digestion Chewing, peristalsis Churning, mixing Peristalsis, mixing Large intestine Resident bacteria in the colon digest material in chyme. Vitamin-K and some B-complex vitamins are released by these bacteria.

  22. Large Intestine: absorption and elimination • Absorption of water and electrolytes • Concentration & elimination of solids • Home for bacteria that produce biotin, folic acid, vitamin K, several B-vitamins, gases • Areas of Colon • Cecum • Rectum • Terminates at anus

  23. Hormones coordinate secretion of digestive juices in the alimentary canal

  24. Liver Entero- gastrone Gall- bladder Gastrin CCK Stomach Pancreas Secretin Duodenum CCK Key Stimulation Inhibition Hormones coordinate secretion of digestive juices in the alimentary canal

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