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Digestive System http://www.hhmi.org/biointeractive/media/fate_of_fat-lg.mov
 
Histology of Digestive Tract <ul><li>Epithelial layer is stratified squamous in mouth, esophagus, and anal canal – protect...
Digestion   <ul><li>Digestion breaks food into small molecules to facilitate absorption </li></ul><ul><ul><li>Chemical and...
Enzymes <ul><li>Speed up chemical reactions in the body </li></ul><ul><li>Proteins, usually ends in -ase </li></ul><ul><li...
Digestion in the Mouth <ul><li>Mechanical digestion (mastication or chewing) </li></ul><ul><li>Chemical digestion </li></u...
 
Composition and Functions of Saliva <ul><li>99.5% water and 0.5% solutes </li></ul><ul><ul><li>Bicarbonate ions buffer aci...
Structure and Function of the Tongue <ul><li>Muscles move tongue to assist in chewing and swallowing </li></ul><ul><li>Pap...
Dentition <ul><li>Primary or baby teeth </li></ul><ul><ul><li>20 teeth that start erupting at 6 months </li></ul></ul><ul>...
Esophagus <ul><li>Collapsible muscular tube, passageway </li></ul><ul><li>10 inches long </li></ul><ul><li>Anterior to ver...
Disorders <ul><li>Achalasia – lower esophageal sphincter fails to relax, meal stuck in esophagus </li></ul><ul><li>Heartbu...
Stomach--M echanical Digestion <ul><li>peristaltic movements called mixing waves. </li></ul><ul><li>Pyloric sphincter rema...
Stomach--Chemical Digestion <ul><li>Salivary amylase continues to work </li></ul><ul><li>Secretion of HCl inactivates amyl...
Absorption in the Stomach <ul><li>Epithelial cells are impermeable to most materials </li></ul><ul><li>Water  </li></ul><u...
Anatomy of Stomach
Stomach Lining
 
Disorders <ul><li>Peptic ulcer Disease </li></ul><ul><ul><li>H. pylori bacterium </li></ul></ul><ul><ul><li>Pain relievers...
Composition and Functions of Pancreatic Juice <ul><li>1 & 1/2 Quarts/day at pH of 7.1 to 8.2 </li></ul><ul><li>Contains wa...
Histology of the Pancreas <ul><li>Acini </li></ul><ul><ul><li>Exocrine  </li></ul></ul><ul><ul><li>99% of gland </li></ul>...
Bile Production <ul><li>One quart of bile/day is produced by the liver </li></ul><ul><ul><li>yellow-green in color & pH 7....
Anatomy of the Small Intestine <ul><li>Major events of digestion and absorption occur in small intestine </li></ul><ul><li...
Histology of Small Intestine
Cells of Intestinal Glands
Chemical Digestion in Small Intestine <ul><li>Chyme entering small intestine contains partially digested carbohydrates, pr...
Review: Digestion of  Carbohydrates <ul><li>Mouth---salivary amylase </li></ul><ul><li>Duodenum----pancreatic amylase </li...
Review: Digestion of  Proteins <ul><li>Stomach </li></ul><ul><ul><li>HCl denatures or unfolds proteins </li></ul></ul><ul>...
Review: Digestion of  Lipids <ul><li>Mouth----lingual lipase </li></ul><ul><li>Most lipid digestion, in an adult, occurs i...
Where will the absorbed nutrients go?
Anatomy of Large Intestine 5 feet long by 2½ inches in diameter
Disorders <ul><li>Appendicitis – inflammation of appendix </li></ul><ul><ul><li>Due to blockage or bacterial infection </l...
Histology of Large Intestine <ul><li>Mucosa </li></ul><ul><ul><li>smooth tube -----no villi or plica </li></ul></ul><ul><u...
Digestion in Large Intestine <ul><li>Mechanical digestion includes peristalsis </li></ul><ul><li>Chemical digestion - bact...
Absorption & Feces Formation  <ul><li>Some electrolytes (Na+ and  Cl-) and vitamins  </li></ul><ul><li>After 3 to 10 hours...
Absorption of W ater   <ul><li>9 liters of fluid dumped into GI tract each day </li></ul><ul><li>Small intestine reabsorbs...
Timing <ul><li>After food is chewed and swallowed – 5-10 seconds to pass down esophagus to stomach </li></ul><ul><li>Parti...
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Transcript of "Digestive System http://www.hhmi.org/biointeractive/media ..."

  1. 1. Digestive System http://www.hhmi.org/biointeractive/media/fate_of_fat-lg.mov
  2. 3. Histology of Digestive Tract <ul><li>Epithelial layer is stratified squamous in mouth, esophagus, and anal canal – protection </li></ul><ul><li>Stomach and intestines are lined by simple columnar epithelium – secretion and absorption </li></ul>
  3. 4. Digestion <ul><li>Digestion breaks food into small molecules to facilitate absorption </li></ul><ul><ul><li>Chemical and Mechanical </li></ul></ul><ul><ul><li>Aided by enzymes </li></ul></ul>
  4. 5. Enzymes <ul><li>Speed up chemical reactions in the body </li></ul><ul><li>Proteins, usually ends in -ase </li></ul><ul><li>Convert substrate to product without being changed </li></ul><ul><li>http://programs.northlandcollege.edu/biology/Biology1111/animations/enzyme.swf </li></ul>
  5. 6. Digestion in the Mouth <ul><li>Mechanical digestion (mastication or chewing) </li></ul><ul><li>Chemical digestion </li></ul><ul><ul><li>Salivary amylase </li></ul></ul><ul><ul><ul><li>begins starch digestion at pH of 6.5 or 7.0 </li></ul></ul></ul><ul><ul><ul><li>swallowed too quickly for all starches to break down; Continues to digest for another hour; Stomach acid inactivates </li></ul></ul></ul><ul><ul><ul><li>Substrate – starch </li></ul></ul></ul><ul><ul><ul><li>Product - maltose </li></ul></ul></ul>
  6. 8. Composition and Functions of Saliva <ul><li>99.5% water and 0.5% solutes </li></ul><ul><ul><li>Bicarbonate ions buffer acidic foods (pH 6.35-6.85) </li></ul></ul><ul><ul><li>Chemical digestion of starch begins with enzyme (salivary amylase) </li></ul></ul><ul><ul><li>Mucus lubricates food </li></ul></ul><ul><ul><li>Enzyme (lysozyme) ---helps destroy bacteria </li></ul></ul>
  7. 9. Structure and Function of the Tongue <ul><li>Muscles move tongue to assist in chewing and swallowing </li></ul><ul><li>Papillae are the bumps---taste buds </li></ul><ul><li>Lingual glands secrete mucus and serous fluid with enzyme lipase </li></ul>
  8. 10. Dentition <ul><li>Primary or baby teeth </li></ul><ul><ul><li>20 teeth that start erupting at 6 months </li></ul></ul><ul><ul><li>1 new pair of teeth per month </li></ul></ul><ul><li>Permanent teeth </li></ul><ul><ul><li>32 teeth that erupt between 6 and 12 years of age </li></ul></ul><ul><ul><li>incisors for biting, canines for tearing, premolars & molars for crushing and grinding food </li></ul></ul><ul><ul><li>Often not enough room for third molars (wisdom teeth) </li></ul></ul>
  9. 11. Esophagus <ul><li>Collapsible muscular tube, passageway </li></ul><ul><li>10 inches long </li></ul><ul><li>Anterior to vertebrae </li></ul><ul><li>Posterior to trachea </li></ul><ul><li>Posterior to the heart </li></ul><ul><li>Pierces the diaphragm at hiatus </li></ul><ul><ul><li>hiatal hernia </li></ul></ul>
  10. 12. Disorders <ul><li>Achalasia – lower esophageal sphincter fails to relax, meal stuck in esophagus </li></ul><ul><li>Heartburn – lower esophageal sphincter fails to close after food enters stomach </li></ul>
  11. 13. Stomach--M echanical Digestion <ul><li>peristaltic movements called mixing waves. </li></ul><ul><li>Pyloric sphincter remains almost, but not completely, closed </li></ul><ul><li>Gastric emptying – about 3mL of chyme is forced out </li></ul><ul><li>Most chyme is forced back into body of stomach to continue mixing </li></ul>
  12. 14. Stomach--Chemical Digestion <ul><li>Salivary amylase continues to work </li></ul><ul><li>Secretion of HCl inactivates amylase, activates lingual lipase and pepsinogen, kills microbes, and stimulates secretion of hormones that promote bile and pancreatic juice </li></ul><ul><li>Protein digestion </li></ul><ul><li>Fat digestion </li></ul>
  13. 15. Absorption in the Stomach <ul><li>Epithelial cells are impermeable to most materials </li></ul><ul><li>Water </li></ul><ul><li>Electrolytes </li></ul><ul><li>Short-chain fatty acids </li></ul><ul><li>Some drugs (especially aspirin) & alcohol </li></ul><ul><li>Gastric mucosal cells contain alcohol dehydrogenase that converts some alcohol to acetaldehyde-----more of this enzyme found in males than females </li></ul>
  14. 16. Anatomy of Stomach
  15. 17. Stomach Lining
  16. 19. Disorders <ul><li>Peptic ulcer Disease </li></ul><ul><ul><li>H. pylori bacterium </li></ul></ul><ul><ul><li>Pain relievers </li></ul></ul><ul><ul><li>Hypersecretion of HCl </li></ul></ul>
  17. 20. Composition and Functions of Pancreatic Juice <ul><li>1 & 1/2 Quarts/day at pH of 7.1 to 8.2 </li></ul><ul><li>Contains water, enzymes & sodium bicarbonate </li></ul><ul><li>Digestive enzymes </li></ul><ul><ul><li>pancreatic amylase and pancreatic lipase </li></ul></ul><ul><ul><li>Pancreatic nucleases </li></ul></ul><ul><ul><li>Pancreatic trypsin (protease) </li></ul></ul>
  18. 21. Histology of the Pancreas <ul><li>Acini </li></ul><ul><ul><li>Exocrine </li></ul></ul><ul><ul><li>99% of gland </li></ul></ul><ul><li>Islets of Langerhans </li></ul><ul><ul><li>Endocrine </li></ul></ul><ul><ul><li>1% of gland </li></ul></ul>
  19. 22. Bile Production <ul><li>One quart of bile/day is produced by the liver </li></ul><ul><ul><li>yellow-green in color & pH 7.6 to 8.6 </li></ul></ul><ul><li>Components </li></ul><ul><ul><li>Water, cholesterol, bile salts, bile pigments (bilirubin) from hemoglobin molecule </li></ul></ul><ul><li>Functions </li></ul><ul><ul><li>Emulsification </li></ul></ul><ul><li>Produced by hepatocytes in liver, stored in gallbladder </li></ul>
  20. 23. Anatomy of the Small Intestine <ul><li>Major events of digestion and absorption occur in small intestine </li></ul><ul><li>Large surface area </li></ul><ul><li>3 parts </li></ul><ul><ul><li>duodenum---10 inches </li></ul></ul><ul><ul><li>jejunum---8 feet </li></ul></ul><ul><ul><li>ileum---12 feet </li></ul></ul><ul><li>Small diameter </li></ul>
  21. 24. Histology of Small Intestine
  22. 25. Cells of Intestinal Glands
  23. 26. Chemical Digestion in Small Intestine <ul><li>Chyme entering small intestine contains partially digested carbohydrates, proteins, and lipids </li></ul><ul><li>The completion of the digestion is a collective effort of pancreatic juice, bile, and intestinal juice in the small intestine </li></ul><ul><li>Occurs in duodenum </li></ul>
  24. 27. Review: Digestion of Carbohydrates <ul><li>Mouth---salivary amylase </li></ul><ul><li>Duodenum----pancreatic amylase </li></ul><ul><li>Brush border enzymes (maltase, sucrase & lactase) act on disaccharides </li></ul><ul><ul><li>produces monosaccharides--fructose, glucose & galactose </li></ul></ul><ul><ul><li>lactose intolerance (no enzyme; bacteria ferment sugar)--gas & diarrhea </li></ul></ul>
  25. 28. Review: Digestion of Proteins <ul><li>Stomach </li></ul><ul><ul><li>HCl denatures or unfolds proteins </li></ul></ul><ul><ul><li>pepsin turns proteins into small polypeptides </li></ul></ul><ul><li>Pancreas </li></ul><ul><ul><li>Pancreatic trypsin--split peptide bonds between amino acids </li></ul></ul><ul><li>brush border enzymes-----aminopeptidase or dipeptidase </li></ul>
  26. 29. Review: Digestion of Lipids <ul><li>Mouth----lingual lipase </li></ul><ul><li>Most lipid digestion, in an adult, occurs in the small intestine. </li></ul><ul><ul><li>emulsification by bile </li></ul></ul><ul><ul><li>pancreatic lipase---splits triglycerides into fatty acids & monoglycerides </li></ul></ul>
  27. 30. Where will the absorbed nutrients go?
  28. 31. Anatomy of Large Intestine 5 feet long by 2½ inches in diameter
  29. 32. Disorders <ul><li>Appendicitis – inflammation of appendix </li></ul><ul><ul><li>Due to blockage or bacterial infection </li></ul></ul><ul><ul><li>Can rupture and spread to abdomen </li></ul></ul>
  30. 33. Histology of Large Intestine <ul><li>Mucosa </li></ul><ul><ul><li>smooth tube -----no villi or plica </li></ul></ul><ul><ul><li>Micro-villi of absorptive cells are present </li></ul></ul><ul><ul><li>simple columnar cells absorb water & goblet cells secrete mucus </li></ul></ul>
  31. 34. Digestion in Large Intestine <ul><li>Mechanical digestion includes peristalsis </li></ul><ul><li>Chemical digestion - bacteria </li></ul><ul><ul><li>undigested carbohydrates into carbon dioxide & methane gas </li></ul></ul><ul><ul><li>undigested proteins into simpler substances (odor) </li></ul></ul><ul><ul><li>turn bilirubin into simpler substances that produce color </li></ul></ul><ul><ul><li>Bacteria produce vitamin K and B in colon </li></ul></ul>
  32. 35. Absorption & Feces Formation <ul><li>Some electrolytes (Na+ and Cl-) and vitamins </li></ul><ul><li>After 3 to 10 hours, Feces are semisolid </li></ul><ul><li>Feces = dead epithelial cells, undigested food such as cellulose, bacteria (live & dead) </li></ul><ul><li>90% of H2O has been removed from chyme in small intestine, but large intestine absorbs enough water to make it important in maintaining water balance </li></ul>
  33. 36. Absorption of W ater <ul><li>9 liters of fluid dumped into GI tract each day </li></ul><ul><li>Small intestine reabsorbs 8 liters </li></ul><ul><li>Large intestine reabsorbs 90% of that last liter </li></ul>
  34. 37. Timing <ul><li>After food is chewed and swallowed – 5-10 seconds to pass down esophagus to stomach </li></ul><ul><li>Partial digestion in stomach – 2-6 hours </li></ul><ul><li>Final digestion and absorption in small intestine – 5-6 hours </li></ul><ul><li>In 12-24 hours undigested material passes through large intestine </li></ul>
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