GIT

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GIT

  1. 1. SECRETIONS OF GASTRO INTESTINAL TRACT PRESENTATION ( GIT )
  2. 3. TYPES <ul><li>Secretions are of two main types: </li></ul><ul><li>Mucus </li></ul><ul><li>Enzymes </li></ul><ul><li>Secretions are produced in response to presence of food in alimentary tract. </li></ul>
  3. 4. MECHANISM OF STIMULATION OF GLANDS <ul><li>Stimulation of Enteric Nervous Stimuli By; </li></ul><ul><ul><ul><li>Tactile Stimulation </li></ul></ul></ul><ul><ul><ul><li>Chemical Irritation </li></ul></ul></ul><ul><ul><ul><li>Distention of the Gut. </li></ul></ul></ul><ul><li>Autonomic Parasympathetic Stimulation: </li></ul><ul><ul><ul><li>Increases the rate of glandular secretion . </li></ul></ul></ul><ul><li>Sympathetic Stimulation: </li></ul><ul><ul><ul><li>Usually reduces the secretions . </li></ul></ul></ul><ul><li>Hormonal Stimulation: </li></ul><ul><ul><ul><li>May increase or decrease the secretions. </li></ul></ul></ul><ul><ul><ul><li>Chemically Gastrointestinal hormones one polypeptides or </li></ul></ul></ul><ul><ul><ul><li>polypeptide devirativer. </li></ul></ul></ul>
  4. 5. MECHANISM OF SECRETION OF GLANDS <ul><li>Secretion Of Organic Substance; </li></ul><ul><li>Nutrient material is provided by the blood. </li></ul><ul><li>Mitochondria forms ATP. </li></ul><ul><li>Rough Endoplasmic reticulum & Golgi complex forms organic substance by nutrients using ATP. </li></ul><ul><li>Secretory vesicles formed are stored until nervous or hormonal signals are arrived to extrude them through cells. </li></ul>
  5. 6. <ul><li>Postulated Mechanism of Secretion; </li></ul><ul><li>Cel ions are actively secreted to the cells interior. </li></ul><ul><li>Followed by passive movement of Na+ ions to cells interior. </li></ul><ul><li>Resulting osmosis of water causes increased volume & hydrostatic pressure. </li></ul><ul><li>Pressure causes excretion of water, electrolytes and organic substance through the cell. </li></ul>WATER AND ELECTROLYTE SECRETION
  6. 7. <ul><li>Salivary Glands; </li></ul><ul><li>Parotia. </li></ul><ul><li>Submandibular. </li></ul><ul><li>Sublingual. </li></ul><ul><li>Buccal. </li></ul>SECRETIONS OF SALIVA
  7. 8. <ul><li>Daily Secretion of Saliva is 1000ml,which consist of; </li></ul><ul><li>Serous Secretion. </li></ul><ul><li>Containing Ptyalin (x-amylase) </li></ul><ul><li>i-e; Enzymatic Secretion for digestion of starches. </li></ul><ul><li>Mucus Secretion. </li></ul><ul><li>Containing mucin for lubrication & protective purposes. </li></ul><ul><li>PH of Saliva is : 6.0 – 7.0 </li></ul><ul><li>Ion Secretion. </li></ul><ul><li>Contains large quantites of potassium & bicarbonate ions and chloride ions. </li></ul><ul><li>Potassium and bicarbonate ions and chloride ions so that during resting conditions sodium and chloride ions are 15,/Eq/L each, </li></ul><ul><li>Potassium about 30mEq/L and Bicarbonate 50-70 mEq /L. </li></ul>TYPES OF SECRETION
  8. 9. <ul><li>Saliva helps to prevent detriorative processes; </li></ul><ul><li>Washes the buccal cavity. </li></ul><ul><li>Thiocyanate ions and proteolytic enzymes. </li></ul><ul><li>Destroy bacteria. </li></ul><ul><li>Digest food particles. </li></ul><ul><li>Antibodies present in saliva prevent dental carries. </li></ul>FUNCTION OF SALIVA
  9. 10. <ul><li>Entirely mucus in character, </li></ul><ul><li>Two types of glands: </li></ul><ul><li>Simple mucus glands, </li></ul><ul><li>In main body of Esophagus. </li></ul><ul><li>Compound mucus glands, </li></ul><ul><li>at the initial & gastric ends of Esophagus. </li></ul>ESOPHAGEAL SECRETION
  10. 11. <ul><li>Two types of glands, </li></ul><ul><li>Oxyntic glands. </li></ul><ul><li>Pyloric glands. </li></ul><ul><li>The Oxyntic Glands Secrete : </li></ul><ul><li>Hydrochloric Acid. </li></ul><ul><li>Pepsinogen. </li></ul><ul><li>Intrinsic Factor. </li></ul><ul><li>Mucus. </li></ul><ul><li>Form the prosimal 80 % of stomach. </li></ul><ul><li>Pyloric Glands Secrete : </li></ul><ul><li>Mucus </li></ul><ul><li>Gastrin. </li></ul><ul><li>These forms distal 20 % of the stomach . </li></ul>GASTRIC SECRETION
  11. 12. <ul><li>Oxyntic glands are composed of three types of cells, </li></ul><ul><li>Mucous neck cells </li></ul><ul><li>Secrete mainly mucus. </li></ul><ul><li>Peptic (Chief) cells </li></ul><ul><li>Secrete pepsinogen. </li></ul><ul><li>Parietal (Oxyntic) Cells </li></ul><ul><li>Secrete HCL and intrinsic factor . </li></ul>SECRETIONS FROM OXYNTIC GLANDS
  12. 13. <ul><li>There are 160 mill moles of HCL in parietal cell secretion, </li></ul><ul><li>PH is about: 0.8 </li></ul><ul><li>1500 calories of energy is required for achieving this acidity concentration which is about 3 million times that of artericel blood. </li></ul>MECHANISM OF HCL SECRETION
  13. 14. <ul><li>Parietal cell contains large branching canalicuki having villus like projections which the HCL is formed. </li></ul><ul><li>STEP 1: </li></ul><ul><li>Cl- ions are actively secreted from cell cytoplasm to the canaliculus. </li></ul><ul><li>Na+ ions are transported out of canaliculus, </li></ul><ul><li>Create a –ive potential of -40 to -70 mv in canaliculus. </li></ul><ul><li>Result in transport of K+ ions to the canaliculus . </li></ul>MECHANISM: continued...
  14. 15. <ul><li>STEP 2: </li></ul><ul><li>Dissociation of Water. </li></ul><ul><li>Provided H+ ions to be transported to canaliculus for the formation of HCL. </li></ul><ul><li>Na+ are actively reabsorbed. </li></ul><ul><li>STEP 3: </li></ul><ul><li>Water passes by osmosis inside the canaliculus. </li></ul><ul><li>Thus FINAL COMPOSITION is: </li></ul><ul><li>Water. </li></ul><ul><li>HCL 150-160 mEq /L. </li></ul><ul><li>Potassium chloride: 15 mEq /L. </li></ul><ul><li>Small amount of Nacl. </li></ul>X CONTINUED... CONTINUED...
  15. 16. <ul><li>STEP 4: </li></ul><ul><li>Co2 combines with Hydroxyl ions to form bicarbonate ions: </li></ul><ul><li>Co2 + Oh ------  Hco 3 </li></ul><ul><li>Which is transported out of cell in exchange of Cl- ions. </li></ul>X CONTINUED...
  16. 17. <ul><li>Secreted by the peptic cells in slightly different forms but all performs the same function. </li></ul><ul><li>Activation of Pepsinogen: </li></ul><ul><li>Pepsinogen is zymogen form of enzyme pepsin. </li></ul><ul><li>Activated by HCL. </li></ul><ul><li>Pepsinogen having molecular weight 42,5000 is split to form pepsin of molecular weight 35000. </li></ul><ul><li>Pepsin is an active proteolytic enzyme requiring acidic medium for its function. </li></ul>SECRETION OF PEPSINOGEN
  17. 18. <ul><li>Intrinsic factor is essential for absorption of Vit.B12. </li></ul><ul><li>Secreted with HCL by parietal cells. </li></ul><ul><li>Thus destruction of parietal cells causes. </li></ul><ul><li>Achlorydria as well as </li></ul><ul><li>Pernicious anemia. </li></ul>SECRETION OF INTRINSIC FACTOR
  18. 19. <ul><li>Secretion of Mucus & Gastrin </li></ul><ul><li>Pyloric glands contain </li></ul><ul><li>Mostly Mucous cells. </li></ul><ul><li>Few peptic cells. </li></ul><ul><li>No parietal cells. </li></ul><ul><li>So the Secretions are; </li></ul><ul><li>A small amount of pepsinogen. </li></ul><ul><li>Large amount of mucus. </li></ul><ul><li>Hormone: Gastrin------Plays a role in controlling gastric secretio. </li></ul><ul><li>The stomach wall is also lined by surface mucous cells. </li></ul>PYLORIC GLANDS
  19. 20. <ul><li>Ecl cells- EnteroChromafin like cells are the cells that are lying deep to oxyntic glands & secrete Histamine in direct contact with the parietal cells. </li></ul><ul><li>So ECL cells can control HCL secretion by producing histamine and histamine secretion can be controlled by; </li></ul><ul><li>Gastrin Secretion. </li></ul><ul><li>Acetylcholine-released from vagal nerve endings. </li></ul><ul><li>Hormonal substances-secreted by enteric nervous system. </li></ul>ROLES OF ECL CELLS IN THE SECRETION OF HCL
  20. 21. <ul><li>Gastrin secreted by G cells of the pyloric glands is a polypepticle having 2 forms; </li></ul><ul><li>G34-containing 34 amino acids. </li></ul><ul><li>G-17-containing 17 amino acids. </li></ul><ul><li>The meats or protein containing foods causes release of gastrin which then reaches the ECL cells & releases Histamine that causes Hcl secretion . </li></ul>CONTROL OF HCL SECRETION BY GASTRIN
  21. 22. REGULATION OF PEPSINOGEN SECRETION Secretion of pepsinogen occurs in response to; Peptic cell stimulation by: Acetycholine Acid in the stomach. 1 2
  22. 23. GASTRIC SECRETION DURING THE INTERDIGESTIVE PERIOD <ul><li>Interdigestive Period; </li></ul><ul><li>The duration in which little or no </li></ul><ul><li>digestion is occurring. </li></ul><ul><li>The secretions during this period; </li></ul><ul><li>non- oxyntic type-containing almost no acid. </li></ul><ul><li>Little pepsin. </li></ul><ul><li>Large amount of mucus. </li></ul>
  23. 24. THANK YOU

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