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Digestive System 1  (upper digestive system) Presented by:   Leo Cheung Chi Man
Objectives: <ul><li>Identify the organs of the digestive tract and the accessory organs of digestion </li></ul><ul><li>Lis...
Digestive System: Overview
Digestive Process <ul><li>There are six essential activities:   </li></ul><ul><li>Ingestion </li></ul><ul><li>Propulsion <...
Part1: The Mouth (Oral or Buccal Cavity)
Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Its functions include: </li></ul><ul><ul><li>Analysis of material before ...
Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Source and composition of   saliva: </li></ul><ul><li>Secreted from cells...
Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Functions of saliva: </li></ul><ul><ul><li>Cleanses the mouth </li></ul><...
Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Carbohydrate Digestion  </li></ul><ul><ul><li>Begins in the mouth   </li>...
Part2: The Pharynx and esophagus <ul><li>Functions: </li></ul><ul><ul><li>They contribute nothing to digestion but  provid...
Part3: The Stomach <ul><li>Muscularis – has an additional oblique layer that </li></ul><ul><ul><li>Allows the stomach to c...
Part3: The Stomach <ul><li>Functions: </li></ul><ul><ul><li>They Bulk storage of undigested food </li></ul></ul><ul><ul><l...
Part3: The Stomach <ul><li>Epithelial lining is composed of : </li></ul><ul><ul><li>Goblet cells that produce a coat of al...
<ul><li>Mucous cells   – secrete mucus </li></ul><ul><li>Parietal (oxyntic) cells   –  secrete HCl and intrinsic factor  <...
Part3: The Stomach <ul><li>Protein Digestion  </li></ul><ul><ul><li>pepsin in the stomach  </li></ul></ul><ul><ul><li>Vide...
<ul><li>Neural and hormonal mechanisms regulate the release of gastric juice </li></ul><ul><li>Stimulatory and inhibitory ...
 
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  1. 1. Digestive System 1 (upper digestive system) Presented by: Leo Cheung Chi Man
  2. 2. Objectives: <ul><li>Identify the organs of the digestive tract and the accessory organs of digestion </li></ul><ul><li>List the six main functions of the digestive system </li></ul><ul><li>Explain how ingested materials are propelled through the digestive tract </li></ul><ul><li>Describe the mechanism of fluid secretions within the stomach, small and large intestines, including an understanding of how these secretions can be modified by intrinsic and extrinsic regulation </li></ul>
  3. 3. Digestive System: Overview
  4. 4. Digestive Process <ul><li>There are six essential activities: </li></ul><ul><li>Ingestion </li></ul><ul><li>Propulsion </li></ul><ul><li>Mechanical digestion </li></ul><ul><li>Chemical digestion </li></ul><ul><li>Absorption </li></ul><ul><li>Defecation </li></ul>
  5. 5. Part1: The Mouth (Oral or Buccal Cavity)
  6. 6. Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Its functions include: </li></ul><ul><ul><li>Analysis of material before swallowing </li></ul></ul><ul><ul><li>Mechanical processing by the teeth, tongue, and palatal surfaces </li></ul></ul><ul><ul><li>Lubrication </li></ul></ul><ul><ul><li>Limited digestion </li></ul></ul>
  7. 7. Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Source and composition of saliva: </li></ul><ul><li>Secreted from cells of salivary glands </li></ul><ul><li>A 97 - 99.5% water, hypotonic, slightly acidic solution containing </li></ul><ul><ul><li>Electrolytes: Na + , K + , Cl – , PO 4 2– , HCO 3 – </li></ul></ul><ul><ul><li>Digestive enzyme: salivary amylase </li></ul></ul><ul><ul><li>Proteins: RNAase, DNAase, lysozyme, peroxidase, and IgA etc… </li></ul></ul><ul><ul><li>Metabolic wastes: urea and uric acid </li></ul></ul>
  8. 8. Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Functions of saliva: </li></ul><ul><ul><li>Cleanses the mouth </li></ul></ul><ul><ul><li>Moistens and dissolves food chemicals </li></ul></ul><ul><ul><li>Aids in bolus formation </li></ul></ul><ul><ul><li>Contains a-amylase that breakdown starch </li></ul></ul>
  9. 9. Part1: The Mouth (Oral or Buccal Cavity) <ul><li>Carbohydrate Digestion </li></ul><ul><ul><li>Begins in the mouth </li></ul></ul><ul><ul><li>Salivary amylase </li></ul></ul><ul><ul><li>V ideo 1 ( http:// www.youtube.com/watch?v =vBtJ1D3S_p8&p=1282F776C2E3DA12&playnext=1&index=12 ) </li></ul></ul>
  10. 10. Part2: The Pharynx and esophagus <ul><li>Functions: </li></ul><ul><ul><li>They contribute nothing to digestion but provide the pathway by which ingested materials reach stomach </li></ul></ul><ul><ul><li>The muscles (smooth and skeletal) in the walls of these segments control swallowing </li></ul></ul><ul><ul><li>Video 2 ( http:// www.youtube.com/watch?v =h0E9ITyRlh0&feature=related ) </li></ul></ul>
  11. 11. Part3: The Stomach <ul><li>Muscularis – has an additional oblique layer that </li></ul><ul><ul><li>Allows the stomach to churn, mix and pummel food physically </li></ul></ul><ul><ul><li>Breaks down food into smaller fragments </li></ul></ul>
  12. 12. Part3: The Stomach <ul><li>Functions: </li></ul><ul><ul><li>They Bulk storage of undigested food </li></ul></ul><ul><ul><li>Mechanical breakdown of food </li></ul></ul><ul><ul><li>Disruption of chemical bonds via acids and enzymes </li></ul></ul><ul><ul><li>Preliminary digestion of proteins with Pepsin </li></ul></ul><ul><ul><li>Production of intrinsic factor required for absorption of vitamin B 12 </li></ul></ul>
  13. 13. Part3: The Stomach <ul><li>Epithelial lining is composed of : </li></ul><ul><ul><li>Goblet cells that produce a coat of alkaline mucus </li></ul></ul><ul><li>Gastric pits containing gastric glands that secrete: </li></ul><ul><ul><li>Gastric juice </li></ul></ul><ul><ul><li>Mucus </li></ul></ul><ul><ul><li>Gastrin </li></ul></ul>The Stomach Lining
  14. 14. <ul><li>Mucous cells – secrete mucus </li></ul><ul><li>Parietal (oxyntic) cells – secrete HCl and intrinsic factor </li></ul><ul><li>Chief (zymogenic/peptic) cells – produce pepsinogen </li></ul><ul><li>Pepsinogen is activated to pepsin by: </li></ul><ul><ul><ul><ul><li>HCl in the stomach </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Pepsin itself by a positive feedback mechanism </li></ul></ul></ul></ul><ul><li>G cells – secrete gastrin </li></ul>Part3: The Stomach Gastric Secretory Cells
  15. 15. Part3: The Stomach <ul><li>Protein Digestion </li></ul><ul><ul><li>pepsin in the stomach </li></ul></ul><ul><ul><li>Video 3 ( http:// www.youtube.com/watch?v =Q-n_Q0qKXzg&feature=related ) </li></ul></ul>
  16. 16. <ul><li>Neural and hormonal mechanisms regulate the release of gastric juice </li></ul><ul><li>Stimulatory and inhibitory events occur in three phases </li></ul><ul><ul><li>Cephalic (reflex) phase: prior to food entry </li></ul></ul><ul><ul><li>Gastric phase: once food enters the stomach </li></ul></ul><ul><ul><li>Intestinal phase: as partially digested food enters the duodenum </li></ul></ul>Part3: The Stomach Regulation of Gastric Secretion
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