digestive system review.txt

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  1. Digestive System
  2. Pharynx & Esophagus
    Involved in TRANSPORT
  3. Stomach
    • Mechanical Disruption
    • Absorption of H20 & alcohol
    • Chyme empties through the pyloric valve
  4. Small Intestine
    Chem. & Mech. digestion & Absorption
  5. Large Intestine
    Absorbs: Electrolytes & Vitamins (B&K)
  6. Rectum & Anus
  7. GI Tract Layers
    • 1. Mucosal
    • 2. submucosal
    • 3. muscularis
    • 4. serosa
  8. Peritoneum
    Visceral layer that covers organs
  9. Peritonitis
    • Accute INFLAMMATION of the peritoneum
    • CAUSE: contamination by infectious microbes during SURGERY or from rupture of abdominal organs
  10. Saliva functions
    • 1. wet food to swallow easier
    • 2. dissolves food for tasting
    • 3. chem. digestion of STARCH starts here (salivary amylase)
    • 4. lysozyme helps destroy bac.
    • 5. prevents INFECTION as it has rinsing action
  11. During INCREASE in salivation
    • sight, smell, sounds, memory of food, tongue stimulation - rock in mouth
    • parasympathetic nn (CN 7&9)
  12. When Salivation is STOPPED
    • dry mouth when you are afraid
    • SYMPATHETIC nerves acting
  13. Mumps (action and symptoms)
    • Attacks the PAROTID gland
    • Vaccine available (since 1967)
    • Symptoms:
    • 1. INFLAMMATION & enlargement of parotid gland
    • 2. Fever, sour throat (esp. swallowing sour foods)
    • 3. Swelling on one or both sides
  14. Mechanical Digestion in mouth
    • called Mastication
    • involves: breakdown of food into pieces and MIXES food w/saliva to form a BOLUS
  15. Chemical digestion in mouth
    • amylase: Starch digestion @ pH 6.5-7 in mouth
    • When bolus & enzyme hit pH 2.5, gastric juices hydrolysis END
    • lingual lipase: (secreted by glands in TONGUE) begin BREAKDOWN of triglyerices into Fatty A & glycerol
  16. Esophagus
    • Voluntary phase: tongue pushes food to back of oral cavity
    • Involuntary phase: soft palate & uvula lifted to close off nasopharynx, & vocal cords CLOSE
  17. Steps involved in swallowing (ESOPHAGUS)
    • Upper sphincter relaxes when larynx is lifted
    • Lower sphincter relaxes as food comes towards stomach
  18. Gastroesophageal Reflex disease
    • When LOWER sphincter FAILS to open (feels like chest pain)
    • If lower sphincter fails to CLOSE...stomach acid enters esophagus (causes HEARTBURN-GERD)
  19. If you have a weak sphincter
    • do NOT eat large meals
    • to prevent GERD, avoid: coffee, chocolate, tomatoes, onions, fatty foods & mint
  20. Pyloric sphincter abnormalities
    • PyloroSPASM: muscle fibers of sphincter FAIL to relax, trapping food in stomach, inducing VOMITING
    • Pyloric Stenosis: NARROWING of sphincter, indicated by PROJECTILE vomiting. Needs surgery correction
  21. Mucosa & gastric glands role
    • HCL converts Pepsinogen from CHIEF cell to PEPSIN
    • Intrinsic factor: absorption of vit. B12 for RBC production
    • Gastric hormone
  22. Gastric hormone fxns
    • 1. releases gastric juice
    • 2. increases gastric motility
    • 3. relaxes pyloric sphincter
    • 4. constricts esophageal sphincter, PREVENTING entry (keep it moving)
  23. Types of Mechanical Digestion Processes
    • 1. Gentle mixing waves: every 15-25s, mix BOLUS w/gastric juice = chyme
    • 2. More vigorous waves: go from stomach to pyloric region
    • 3. Intense waves: near pylorus, open & squirt 1-2tsp w/each wave
  24. Chemical Digestion
    • This is where PROTEIN digestion occurs
    • HCL transforms pepsinogen to pepsin and that breaks peptide bonds b/w aa's
    • FAT digestion also continues: triglycerides in milk fat
    • HCL kills microbes (low pH)
    • Mucous cells protect stomach walls from being digested
  25. Vagus nerve
    Increases STOMACH muscle and GLANDULAR activity
  26. Nervous control
    keeps stomach alive
  27. If caffeine or protein present?
    • G-cells secret gastrin into the bloodstream
    • Gastrin hormone INCREASES stomach glandular secretions
    • sphincter relaxation occurs
  28. Intestine role in digestion
    • Stretch receptors in duodenum SLOW stomach activity & increase intestinal activity
    • SYMPATHETIC nerves SLOW stomach activity
    • Hormonal influences: secretin (decreases stomach secretions), CCK (decreases stomach emptying), Gastric inhibitory peptide (decreases stomach secretions, motility & emptying)
  29. When there is distention & stomach contents
    increase in Gastrin hormone SECRETION and Vagal nerve impulses
  30. Pancreatic juice
    • pH of 7.1-8.2
    • contains H20, enzymes & sodium bicarb.
    • has Digestive enzymes
  31. Pancreatitis
    Inflammation of pancreas (occurs with the MUMPS)
  32. What is involved in REGuLATING pancreatic secretions?
    • SECRETIN: high acid in intestine causes increase in sodium bicarb release
    • GIP(gastric inhibitory peptide): f-acid & sugars cause INCREASE insulin release
    • CCK: fats & proteins cause INCREASE digestive enzyme release
  33. Bile
    • 1Qt is secreted by liver per DAY
    • yellow-green
    • composed of H20 & cholesterol & bile salts (Na&K)
    • contains bilirubin - bile pigments
  34. Pathway of bile
    • Flows through bile capillaries into hepatic ducts
    • these ducts form a COMMON hepatic duct
    • the Common hepatic duct joins with Cystic duct to form: COMMON BILE Duct
    • This empties into the DUODENUM
  35. Liver fxns:
    • 1. turns proteins into GLUCOSE
    • 2. turns triglyerides into GLUCOSE, also stores some fat
    • 3. synthesizes cholesterol & lipoproteins
    • 4. stores excess glucose as GLYCOGEN (and can turn back to glucose when needed)
    • 5. detoxifies the blood by removing drugs & hormones
    • 6. Stores vitamins (fat soluble such as ABDEK)
    • 7. Stores Iron & Copper
  36. Location of digestive hormones
    • Gastrin: stomach, gastric & ileocecal sphincters
    • GIP: stomach & pancreas
    • Secretin: Stomach, liver & pancreas
    • CCK: stomach, pancreas, gallbladder, sphincter of Oddi
  37. Microvilli
    • Increases surface area
    • Involved in Absorption & Digestion
  38. Brush border enzymes (types and role)
    • Types: Maltase, Sucrase & Lactase
    • Role: carb digestion- Act on Disaccharides to produce Monosacchardies (fruc, gluc & galac)
  39. lactose intolerant
    • mucosal cells in small intestines fail to produce lactase
    • Essential for digestion of lactose sugar in milk
    • results: diarrhea, gas, abdominal cramps
  40. Protein digestion in stomach
    • HCL denatures proteins
    • Pepsin turns proteins into peptides
  41. Protein digestion in pancreas
    • digestive enzymes: split peptide bonds
    • brush border enzymes: aminjopeptidase or dipeptidase
  42. Lipid Digestion in Mouth
    lingual lipase
  43. Lipid Digestion in Small intestines
    • Fats emulsified by BILE
    • Pancreatic lipase: splits into f acids & monoglycerides
  44. Nucleic Acid digestion
    In pancreatic juice: ribonuclease (digests RNA) & deoxyribonuclease (digests DNA)
  45. Electrolyte Absorption
    Ca+ absorp. requires vit D & PTH (osteoclast activity)
  46. H20 Absorption
    • 9L fluid dumped into GI tract/day
    • Small intestine reabsorbs 8L
    • Large intestine reabsorbs 90% of last L
  47. Large Intestine Mechanical Digestion
    • Haustral churning
    • Gastroilial reflex
    • Gastrocolic reflex: moves FECES into rectum
  48. Large Intestine Chem. Digestion
    • NO enzymes secreted-only mucus
    • bacteria ferment:
    • 1. undigested carbs into CO2 & meth. gas
    • 2. undigested proteins into simpler substances (ie indoles--odor)
    • 3. turn bilirubin into simpler substances that produce color
  49. Large intestine Absorption & feces formation
    • electrolytes absorbed: Na+ & Cl-
    • 3-10hrs, 90% of H20 removed from chyme
    • feces formed: dead epithelial cells, undigested food (ie cellulose), bacteria
  50. Problems w/defecation
    • Diarrhea: chyme passes too quickly thru intestine (not all H20 reabsorbed)
    • Constipation: decreased intestinal MOTILITY (too much H20 reabsorbed). Drink H20, exercise & fiber to remedy
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digestive system review.txt
2011-04-12 22:03:49
digestive system

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