Physiology lecture 5

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9spr
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70176
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Physiology lecture 5
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2011-03-02 14:19:56
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Gastrointesinal Physiology
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  1. objectives
    • overview of small intestine functional anatomy
    • digestion of carbohydrates, protein, fat
    • absorption of sugar
    • absorption of aminoacids and small proteins
    • absorption of fat
  2. overview of the small intestine
    • site of the most absorption and digestion
    • sections: duodenum, jejunum, ileum
    • motility includes: segmentationmigrating and motility complex
  3. lecture notes
    • carbs proteins a lipids are absorbed mainly in the duodenum
    • calcium folat and iron are only absorbed in tthe duodenum
    • bile and acids are mainly absorbed in the ileum
    • cobalamin is only absorbed in the ileum
  4. secretion
    • juice secreted by the small intestine does not contain any digestive enzymes
    • synthesized enzymes ac within the brush border membrane of epithelial cells
    • enzymes: enterokinase, disacharridases, amino peptidases
  5. lecture notes
    • termed succus entericus
    • these peptidases are found on the brush border membrane and will lskdfjlkdfj
  6. Digestion
    • pancreactice enzymes continue carbohydrate and protein digestion
    • brush border enzymes complete digestion of carbohydrates and protein
    • fat is digested entirely withinthe small intestine lumen by pancreatic lipase
  7. lecture notes
  8. Absorption
    • absorbs almost everything presented to it
    • most occurs in duodenum and jejunum
    • surface area is increased by: circular folds with finger like projections on them called villi,. that have brusbhh borader on them know as micro villi that arrise from the luminal surface of epithelial cells
    • lining replaced every 3-5 days
    • products of fat digestion undergo transformationsthat enable them to be passively absorbed (eventually enter the lymph)
  9. lecture notes
    lining replaced 3-5 days
  10. Brush border CHO hydrolases
    • sucrase- breaks downsucrose into 1 glucose and 1 fructose
    • isomoltase- breaks down maltose into 2 glucose
    • lactase breaks down lactose into 1 glucose and 1 galactose
    • these are all monosacharrides
  11. lecture notes
    glucose and galactose
  12. Na Glucose coTransport
    • lumina NA enters through SGLT1 and exists through baso lateral Na, K, ATPase
    • Na solute cotransporters uses the energy of the electro chemical gradient for Na to driveco transported solute above its equilibrium value
    • 2 Na ions are coupled to 1 glucose; intracellular levels of glucose increase 100 fold
  13. lecture notes:
    • cotransport also termed symport
    • Na concentration is high outside the cell and low inside the cell thus driving sodium together with glucose into the cell
    • galactose can also be a substrate other than glucose
    • (cotransported with the SBLT1)
    • glucose enters via the Glut2 and the fructose exits via Glut5
  14. Carbohydrate Digestion and Absorption
  15. lecture notes
    look closely into the picture

    • glut 2 knock out animal still live
    • glucose can also leave via exo cytosis thus allowing the glut 2 knock outs to live
  16. Endopeptidase/ Exo Peptidase
    • endo: digests internal peptide bonds
    • exo: digests terminal bonds to releaseamino acids
  17. lecture notes
    • endo peptidase makes 2 maller peptides
    • exo peptidase
  18. Random stuff
  19. lecture notes
    • SGLCT
    • humming bird eates every 12 minutes
    • python only eats 2 times a year
    • they use same glucose co transporter that humans use (lasts the test of evolution)
  20. Protein Digestion and Absorption
    look closely at the picture
  21. lecture notes
  22. Pep T1
  23. lecture notes
  24. Volume regulation by co transport
  25. digestion of lipids
  26. Bile salts
    • 1: bile salts from liver coat fat droplets
    • 2: pancreatic lipase and colipase break down fats into mono glycerides and fatty acids stored in micelles
    • 3a: monoglycerides and fatty acids move out of micelles and enter cells by diffusion
    • 3b: cholesteral is transportedinto cells by membrane transporter
    • 4: absorbed fats combine with cholesteral and proteinsin the intestinal cells to form chylomicrons
    • 5: chylomicrons are released into the lymphatic system
  27. lecture notes

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