GI2- Equine GI Phys

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  1. Why is chemical digestion in the mouth of the horse minimal?
    unlike other species, there is no amylase
  2. Describe the esophagus of the horse.
    • proximal- striated muscle
    • distal- smooth muscle
  3. Why don't horses regurgitate or vomit?
    horses have a complete cardiac sphincter that is very strong
  4. What is the innervation of the esophagus?
    CN X vagus nerve
  5. What are the 2 big portions of the equine stomach?
    • non-glandular/squamous portion (1/3)
    • glandular portion (2/3) separated by the margo plicatus
  6. What are the functions of the glandular portion of the stomach?
    acid, enzyme, and buffer production
  7. What are the functions of the squamous portion of the stomach?
    mixing and folding feed
  8. The gastric epithelium of the equine stomach is highly ___________ to _________; therefore, the contents have __________.
    impermeable; water; high osmolality
  9. Describe the acid secretion of acid in the equine stomach. What is the clinical significance of this?
    continuous secretion of acid and enzymes (made to graze constantly); therefore, if horses are not eating, they will be predisposed to gastric ulcers
  10. What are the transit times of liquids and particulates through the equine stomach?
    • Liquids: 75% gone by 30 min
    • Particulates: 75% gone by 90 min
  11. Compare the gastric mucosa of foals to adult horses.
    foals have thinner squamous mucosa and higher resting pH than adults
  12. Function of parietal cells of stomach.
    acid secretion via H+K+ATPase pump
  13. Function of chief cells of stomach.
    pepsinogen--> pepsin (protease)
  14. Function of enterochromaffin cells of stomach.
    histamine--> stimulate acid release
  15. Function of D cells of stomach.
    somatostatin--> inhibits acid release
  16. Function of G cells of stomach.
    gastrin--> stimulates acid release
  17. Function of goblet cells of stomach.
    bicarb and mucous release
  18. What drugs are used in horses to increase stomach pH? (2)
    Ranitidine- Zantac (H2 receptor blocker), Omeprazole (PPI)
  19. What pancreatic enzyme in horses has the highest activity?
    lipase (followed by amylase)
  20. What is secreted by the pancreas? (7)
    lipase, amylase, elastase, trypsin, chymotrypsin, bicarb, Cl- (Cl- reclaimed in ileum)
  21. Describe secretion of enzymes and buffers from the pancreas.
    continuous secretion ALL THE TIME
  22. Describe the secretion of biliary secretions from the liver.
    continuous secretion
  23. Function of bile. (2)
    fat digestion and absorption, cholesterol--> cholic + chenodeoxycholic
  24. Bile salts form __________ with __________ for __________ of fat to TG and FFA.
    micelles; lipid; emulsification
  25. Lipases assist with digestion and absorption into ____________ as _____________.
    villus lacteals; chylomicrons
  26. 90% of bile salts are reabsorbed in the _________ and go back to ____________.
    ileum; enterohepatic circulation
  27. In proximal small intestine, most ___________ takes place; in the distal small intestine, most _____________ occurs.
    digestion; absorption
  28. What is the innervation of the small intestine?
    CN X- Vagus nerve
  29. Describe the epithelium of the small intestine.
    columnar mucosal epithelium with villi and microvilli brush border
  30. Function of S cells in the SI.
    secretin stimulates pancreatic and biliary secretion into the SI
  31. What stimulates S cells in the SI?
    acid in the duodenum
  32. What is the function of I cells in the SI?
    CCK stimulates pancreatic and biliary secretions into the SI, decrease gastric emptying and acid production
  33. What stimulates I cells of the SI to secrete CCK?
    stimulated by Ach, FFA, CCK-release factor, AA, fat in SI
  34. What is the precursor molecule for most pancreatic enzymes?
  35. Transcellular absorption is _________ and occurs by...
    active; transporters across a cell membrane.
  36. Paracellular absorption is _________ and occurs by...
    passive; concentration-dependent diffusion between cells.
  37. If there is a dysfunction of ___________ enzyme, polysaccharides and sodium will stay in the lumen, leading to __________.
    lactase; diarrhea
  38. The crypts of Lieberkuhm (intestinal crypts) _________ volume to keep __________.
    volume; chyme fluidity
  39. What are the parts of the intestinal crypts? (4)
    stem, goblet, Paneth, endocrine cells
  40. Intestinal crypts secrete __________ so _________ will follow; this secretion is mediated by __(2)__.
    Cl- and Na+; water; enteric nervous system and prostaglandins
  41. What is the major role of intestinal crypts in diarrhea development?
    prostaglandin-mediated hypersecretory function
  42. What are Paneth cells of the intestinal crypts?
    functionally like neutrophils, secrete anti-microbial substances
  43. What are Brunner's glands of the intestinal crypts?
    produce mucus-rich alkaline secretions to protect mucosa from acid chyme and to facilitate digestion
  44. What is the function of B cells in the intestinal crypts?
    produce secretory IgA
  45. Water permeability of the SI __________ from proximal to distal.
  46. Intraluminal pH of the SI ________ from proximal to distal due to...
    increases; a gradual increase in bicarb and extensive ileal Cl- absorption
  47. What is the migrating motor complex (MMC)?
    interdigestive phase under motilin influence
  48. What is the clinical significance of the large extra-intestinal secretory volumes (fluid absorbed from the GI)?
    if obstruction occurs and these volumes are lost, hypovolemic shock occurs fairly quickly
  49. What is the purpose of the high bacterial counts in the large intestine? (3)
    hind-gut fermentation: bacteria produce VFAs, which supply 30% of horses kcal per day; bacteria also produce essential AAs, FAs, and vitamins (vit K); immune function
  50. What are the types of bacteria within the large intestine? (5)
    anaerobes, cellulytic bacteria, enterobacteria (facultative anaerobes), protozoans, archae
  51. What characteristic lets you know you are in the ventral large colon? What is the purpose of these structures?
    ventral colon haustra (sacculations): mixing movements
  52. What are the neurohormonal controls of mucosal secretion/absorption in the large intestine? (3)
    • RAAS: electrolyte homeostasis, K+ excretion
    • ADH and ANP: balance Na+/ water content (osmolality), aquaporin expression (movement of water)
    • Enteric nervous system: sympathetic (proabsorption), parasympathetic (prosecretion)
  53. How does SNS tone influence the ENS?
  54. How does PNS tone influence the ENS?
  55. What is the highest VFA absorption to the lowest (based on size)?
    acetate>>> propionate>> butyrate
  56. What anatomic sphincters exist to assist with aboral flow through the equine GI tract?
    • lower esophageal sphincter (true)
    • pyloric sphincter (true)
    • ileocecal valve (functional)
    • cecocolic orifice (functional)
  57. The ileal lumen is slightly smaller than the jejunal lumen to allow for...
    macronutrient absorption across jejunal brush border.
  58. What is the purpose of the pelvic flexure narrowing from the left ventral colon?
    allows haustral mixing of ingesta for effective bacterial fermentation
  59. What is an example of a drug that should be avoided in colicky horses and why?
    xylazine because it decreases intestinal motility
  60. Describe the process of protein digestion in the small intestine.
    • 1. proteins digested to AA by pancreatic proteases and brush border enzymes
    • 2. AAs are absorbed by active transport into the absorptive cells and move to the opposite side (transcytosis)
    • 3. AAs leave the villus epithelial cell by facilitated diffusion and enter the capillary via intercellular clefts
  61. Describe the process of absorption of monosaccharides and amino acids in the small intestine.
    • 1. initial luminal digestion (polysaccharides to disaccharides; proteins to polypeptides and peptides)
    • 2. extensive brush border digestion and absorption
    • 3. cotransport with Na+ and H+ ito enterocytes and then to portal vein by transcellular movement
  62. Describe the absorption of monoglycerides and FFAs from the intestinal lumen.
    • 1. luminal digestion of Tags via lipases
    • 2. re-esterification in enterocytes into chylomicrons
    • 3. transport via lacteal to cisterna chyli, thoracic duct, then cranial vena cava
  63. Electrolytes are absorptions from the SI lumen by __(2)__.
    transcellular and paracellular pathways
  64. What are the sources of bicarb in the horse's body? (5)
    saliva, stomach (goblet cells), pancreas, bile, +/- Brunner's glands
Card Set:
GI2- Equine GI Phys
2016-03-08 19:05:14
vetmed GI2

vetmed GI2
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