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55 Cards in this Set
- Front
- Back
- 3rd side (hint)
What causes diarrhea on the molecular level?
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An increase in osmotic particles in the feces which results in an increase in fecal water content
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What are the 3 types of diarrhea (i.e. what are the 3 mechanisms)?
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1) Secretory
-Secretion outpaces absorption 2) Malabsorption/ maldigestion -Failure of food particles to be assimilated or ions to be absorbed 3) Exudative -Leakage of blood or protein into gut lumen |
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How much water do horses ingest daily? Cows? Neonates?
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Horses: 4-6% BW
Cows: 7-10% BW Neonates: need 10% BW - Will drink 20-25% BW if unlimited water available |
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*The total daily amount of all fluid entering the gut roughly equals ____________________.
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The animal's ECF volume
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How much water that goes into the gut is absorbed before excretion?
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99%
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Where does the majority of intestinal secretion occur? What cells are responsible?
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Upper GI, by cells in crypts of Lieberkuhn's
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Where does the majority of intestinal absorption occur?
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Along the villi of the jejunum and ileum (some occurs in colon)
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Along
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What part of the intestine has a 'reserve capacity'?
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The colon has a reserved capacity to handle extra water, diarrhea occurs when this reserve capacity is overwhelmed or colon is diseased
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Compare the reserve capacities of horses, small ruminants and cattle and hence the hydration of the feces?
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Small ruminants (pelletted feces) > horses > cattle (80-85% water)
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What are the two "cycles" of the intestines?
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1) Front (secretion) to back (absorption) in whole GI tract
2) Bottom (crypt) to top (villus) of each microscopic intestinal segment |
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True or false. Sheep and goats commonly get diarrhea.
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False, have a high reserve capacity so the small intestine and stomach has to be messed up OR colon damaged to get diarrhea
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What electrolyte is used as crypt cells divide to form the mature absorptive cells on the villus?
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Takes in large amounts of NaCl from the interstitium
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Why is chloride excreted into the intestinal lumen?
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After crypt cells take in NaCl during division, the Na is recycled back into the ECF by the Na/K pump and much of the K+ leaks back into the ECF leaving a negative net charge in cell--> Cl- diffuse out of cell into intestinal lumen
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What promotes the facilitated diffusion of luminal Na into the villus cells?
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Villus cells pump Na out of their ICF into the interstitium by basolateral Na/K pump, creating low [Na] in the cell so Na diffuses into cell from lumen
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How is Na+ transported from the intestinal lumen into the villus cells?
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-Na/Glucose co-transport
-In exchange for H+ or K+ while Cl enters in exchange for HCO3- |
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What happens to the bicarbonate that is released from the intestinal villus cells in exchange for Cl?
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Recycled by the body by absorption of CO2 from the combination of luminal H+ and HCO3
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What are the 3 processes that break large food particles down into small particles?
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1) Mechanical
-teeth, stomach 2) Hydrolytic -stomach acid 3) Enzymatic -Starts in mouth w/ amylases -pepsin, trypsin, lipases- pancreas or intestinal brush border, stomach |
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Adequate digestions requires the presence of necessary enzymes, time for them to act and _____________.
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Thorough mixing of ingesta
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What are the 4 major sites of endogenous enzymatic digestion?
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1) Mouth
2) Stomach 3) Cranial duodenum 4) Small intestinal brush border |
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What is the major site of microbial digestion for ruminants? Horses?
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Ruminants: Rumen
Horses: colon |
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The most widely known example of secretory diarrhea is caused by what?
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Cholera and cholera-like toxins, including the heat-labile toxin (LT) of E. coli
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The cholera and cholera-like toxins (+ heat labile toxin of E. coli) enters the cell and appears to do what 2 things?
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1) 40% stimulates adenylate cyclase --> increase intracellular cAMP--> phosphorylation of membrane ion channels --> Cl secretion enhanced and Na loss begins to occur across apical membrane
*2) 60% stimulates the enteric nervous system, which in turn stimulates crypt cell division (increasing rate of Cl loss and pushing off the absorptive apical epithelium-the dividing cells take up lots of NaCl) so cells are changed from 20% secretory and 80% absorptive to 50/50 |
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True or false. Cholera is a major cause of secretory diarrhea in small animals.
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False, Cholera doesn't effect the species we deal, but cholera-like toxins do
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Inflammation can cause ______ intestinal secretion.
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increased
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Maldigestion can be the result of poor _______ or _______, or poor ________ or ________.
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Poor chewing or mixing, or poor digestive enzyme or acid production
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What are the 3 areas of production that can result in maldigestion when damaged?
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1) Gastric ulcers
2) Parasitic or microbial damage to gastric pits or villus cells 3) Liver or pancreatic disease |
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What is a major cause of mild maldigestive diarrhea in large animals?
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Inadequate microbial digestion due to die-offs in the normal population and feed changes
----> large undigested particles draw water into the bowel |
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What are the 2 causes of malabsorption?
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1) Loss of surface area of the gut
2) Thickening of the gut wall |
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What causes a loss of surface area of the gut resulting in malabsorption?
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Occurs acutely w/ microbial or toxic damage; with time, blunted villi may form, leading to physiologic, chronic malabsorptive diarrhea
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What are 4 causes of thickening of the gut, resulting in malabsorptive diarrhea?
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1) Neoplasia
2) Fibrous reactions 3) Inflammatory cell infiltrates 4) Edema |
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What are the 3 causes of edema (which can result in malabsorptive diarrhea)?
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1) Vasculitis
2) Hypoproteinemia 3) Passive congestion of blood vessels or lymphatics |
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How do alterations in intestinal motility lead to osmotic diarrhea?
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By affecting digestion and absorption
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What are the sequelae to slowed transit or an atonic gut?
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Slow transit is often accompanied by poor mixing cycles, meaning that food particles are not brough into contact w/ the brush border for digestion or absorption. Also microbial fermentation in an atonic gut leads to production of osmotic particles
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What are the sequelae to increased gut motility?
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May decrease the amount of time available for absorption
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What are the digestive repercussions of ostergia in cattle or haemonchus in sheep?
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Can damage the acid secreting part of the intestine resulting in maldigestion
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What is the primary cause of exudative diarrhea?
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Usually result of inflammatory processes affecting the bowel.
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What is an example of acute exudative diarrhea? Chronic?
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Acute: Hemorrhagic gastroenteritis
Chronic: Johne's disease |
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What is the mechanism of action of exudative diarrhea?
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Loss of mucosal integrity, leading to leakage of protein, plasma or blood into the gut lumen, or an abnormal build-up of pressure and protein in the tissue (as occurs w/ lymphatic obstruction)
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Blood and protein are poorly digested beyond the _______ and hence act as osmotic particles.
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Cranial duodenum
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______ diarrhea are usually more severe than other types, because they reflect a more severe degree of tissue damage.
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Exudative diarrhea
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What are 5 disease processes that could cause thickening of the bowel and result in obstruction of lymph passage?
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1) Neoplasms
2) Tumor 3) Inflammatory bowel disease 4) Non-neoplastic infiltrates 5) Edema |
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True or false. An increase in peristalsis with a decreased intestinal transport time has the potential to decrease time for absorption to take place in the gut, so it causes diarrhea.
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False, it is unlikely that this alone can lead to diarrhea, but if another mechanism is operative, this can exacerbate fluid and electrolyte loss
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How does a decrease in peristalsis or mixing motility cause diarrhea?
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Promotes bacterial overgrowth and fermentation. This can lead to diarrhea through inflammation or the generation of secretagogues or osmotic compounds
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What is the primary purpose of mixing ingesta in the intestines?
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Mix stuff w/ enzymes secreted at brush border or mucosa w a larger amount of stuff in lumen and increase contact b/w luminal contents and gut so absorption can happen
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How is the fecal volume affected by small intestinal disease in small animals? Large intestinal disease?
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SI: increased
LI: Normal |
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Is mucus present when diarrhea is caused by small intestinal disease in small animals? LI?
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SI: rare
LI: common -Mucus is a large intestine lubricant, if irritated it over lubricates |
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How does blood in the stool appear with small intestinal disease in small and large animals? Large intestinal?
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SI: melena
LI: fresh (hematochezia) |
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How often does tenesmus (straining) occur with small intestinal disease in small and large animals? LI disease?
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SI: rare
LI: common |
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How often does vomiting/colic occur with small intestinal disease in small and large animals? LI disease?
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SI: occassional
LI: rare |
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What "type" of diarrhea does salmonellosis cause (secretory, maldigestive/malaborption, exudative)?
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Causes ulcers in GI tract, knocks out the brush border, affects digestion, but also affects absorption and if bad enough animals bleed or leak protein into GI tract so exudative, and malabsorptive/ maldigestive
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How often is there fat present in stool in small animals with small intestinal disease? LI disease?
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SI: Occasional
-normally digested in SI LI: No |
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How common is undigested food present in the stool with small intestinal disease in small animals? LI disease?
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SI: Occasional
LI: Rare |
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How common is urgent defacation with SI disease in small animals? LI disease?
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SI: uncommon
LI: common |
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How common is gas with small intestinal disease in small animals? LI disease?
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SI: occasional
LI: Rare |
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How common is weight loss in small animals with small intestinal disease? LI disease?
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SI: common
LI: rare |
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