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Gastrointestinal System, image, Putu Dyan Stephanie I1401201063 P2…

- - - - breakdown complex carbohydrates
      - three salivary glands
    - - proteins
    - - carbohydrates
      - protein
      - fats
      - nucleic acid
- - - - mucous cells
        
        secretes mucus
        
        protects epithelium from the acid
      - chief cells
        
        secretes pepsinogen
        
        then convert to pepsin
      - parietal cells
        
        secrete intrinsic factor
        
        carrier for absoption of vitamin B12
        
        secrete hydrochloric acid
        
        to convert pepsinogen to pepsin
        
        to provide optimal pH for pepsin
        
        making chyme
        
        kills any bacteria that enters
        
        process
        
        acid secretion increases and reaches a peak by 90 minutes
        
        subsquently falls as food enter small intestine
        
        takes 4 hours to empty stomach after meal
    - - Cephalic Phase
        
        feed forward control
        
        affects fundic parietal cells to increase proton pump activity and increase acid secretion
        
        affects antrum to increase gastrin hormone secretion
        
        stimulates parietal cells
        
        affect eneterochromaffin cells to increase histamine secretion
        
        histamine increase activity of proton pump in parietal cells
        
        smell, thought, and chewing increase secretion
        
        40% of total acid production
      - Gastric Phase
        
        initiated by mechanical distension by food and the arrival of amino acids, alcohol, and caffein within antrum
        
        stimulate secretion of gastrin from G cells of antrum
        
        60% of gastirc acid secretion
      - Inhibition
        
        excess acid can be caustic and acid is only needed in feeding
        
        mediated by stomach luminal pH
        
        feeding
        
        proteins in the chyme act to buffer the pH to usually above 3.0
        
        empty stomach
        
        pH fall below 3
        
        D cells of the antrum secrets somatostatin
        
        inhibit gastrin secretion from G cells
    - - causes
        
        excess use of non-steroidal anti-inflammatory drugs (NSAIDs) which inhibit the production of mucus by the epithelial cells
        
        infection by helicobacter pylori
        
        most commone cause that can be treated with antibiotics
      - Therapy targets
        
        simple buffering of lumenal pH
        
        the fastest effect with bicarbonate or food
        
        inhibition of the pareital cell histamine receptor
        
        the most effective
      - Disruption of this barrier leads to erosion of the epithelium lining the stomach lumen
- - - - epithelium contains mucous glands and goblet cells which secrete mucus to neutralize the pH of the chyme
      - secretes cholecystokinin (CCK) and secretin, which signal the arrival of food to the pancreas, gall bladder, and stomach, respectively
    - - ciliated epithelial cells (microvilli)
        
        increase the absorption area
      - transport mechanism
        
        Simple sugars and amino acids are absorbed by secondary active transport
        
        Di/tri-peptides enter by a symporter (called the PepT)
        
        Fats (lipids) are digested to free fatty acids and cholesterol within the intestinal lumen by lipase
      - ileum
        
        dominant site of water absorption
        
        absorb intrinsic factor vitamin B12 complex and for bile
  - - - Delayed emptying
        
        vomiting
        
        bloating
        
        heartburn
        
        nausea
      - Rapid emptying
        
        anxiety
        
        weakness
        
        dizziness
        
        sweating
        
        diarrhea
    - - caused by an infection (such as cholera vibrio)
      - increased secretion of chloride into the lumen of the ileum
      - Sodium follows chloride and water follows sodium to maintain isotonicity
      - The amount of fluid delivered to the colon exceeds the absorptive capacity of the colon and diarrhea results.
    - - undigested material (lactose) or poorly absorbed solute (such as Epsom salts) is delivered to the colon
      - Water from the body enters the lumen to maintain isotonicity