Term
| What anatomical mechanisms increase the small-intestine surface area? |
|
Definition
|
|
Term
| The large intestine has villi but no _______. |
|
Definition
|
|
Term
| The small intestine (jejunum and ileum) is capable of surface digestion via _______. |
|
Definition
|
|
Term
| Almost all nutrient absorption occurs in the |
|
Definition
|
|
Term
|
Definition
| in the small and large intestine |
|
|
Term
| The large intestine has the ability to _______ sodium. |
|
Definition
|
|
Term
| Four phenotypes on the small intestine epithelium |
|
Definition
| columnar absorptive cells (most numerous), enterochromaffin (endocrine) cells, mucous (goblet cells), and undifferentiated cells |
|
|
Term
| Why does the tip of the villus receive blood with the lowest arterial PO2? |
|
Definition
| as blood flows up the central arteriole, oxygen diffuses down the concentration gradient into the veins draining the villous |
|
|
Term
| During what period is there a depletion in the high energy phosphate bonds required for the production of protective substances such as mucus? |
|
Definition
|
|
Term
| Depressed cell pH regulation lead to ________ ________ in the small intestine. |
|
Definition
|
|
Term
| During tissue acidosis there is |
|
Definition
| release of lysosomal enzymes and tissue digestion |
|
|
Term
| Name the 3 end products of carb digestion that are absorbed into portal blood? |
|
Definition
| glucose, galactose, and fructose |
|
|
Term
| What is the function of bile in the jejunum? |
|
Definition
| emulsify fats by forming a negatively charged aggregate called a micelle to dissolve water insoluble material |
|
|
Term
| After emulsified fats are dissolved inside the micelle how are they absorbed across the brush border? |
|
Definition
| micelles diffuse from the emulsion particle to the brush border where the fat is released to diffuse across the lipid membrane into the cell |
|
|
Term
|
Definition
| uptake of large amounts of intact molecules (usually proteins) by engulfing them via invaginations by phagosomes |
|
|
Term
| What happens after a phagosome has performed pinocytosis? |
|
Definition
| merging with lysosomes to form phagolysosomes where cellular digestion can occur |
|
|
Term
| Why is absorption of intact protein important for the neonate? |
|
Definition
| for obtaining antibodies (passive immunity) from the mother |
|
|
Term
| Pancreatic enzymes adapt quickly to changes in diet, especially when |
|
Definition
|
|
Term
| During the introduction of solid food there is an increase in |
|
Definition
| pancreatic and brush border enzymes |
|
|
Term
| Adaption to dietary protein and fat is mediated by the intestinal hormones |
|
Definition
|
|
Term
| CCK and secretin induce gene expression of |
|
Definition
| pancreatic proteases and lipases |
|
|
Term
| Initiation of brush border enzymes is due to an intrinsic program in the enterocyte regulated by levels of |
|
Definition
| glucocorticoids or thryoxine |
|
|
Term
| What are the carbohydrate sources and absorbable end products of microbial digestion of carbs? |
|
Definition
| sources are soluble starches and insoluble fiber and end products are SCFA's and gases |
|
|
Term
| Horses cannot utilize microbial protein because |
|
Definition
| there is no amino acid transport system in the small intestine |
|
|
Term
| Ruminants can recover the microbial protein in the |
|
Definition
|
|
Term
| The purpose of protein in the large intestine of the horse is to provide |
|
Definition
| nitrogen for microbial protein synthesis |
|
|
Term
| Most of the salt and water that the gut has to reabsorb is derived from what sources? |
|
Definition
|
|
Term
| Herbivores secrete larger amounts of fluid such as saliva that are necessary for |
|
Definition
| forestomach fermentative process |
|
|
Term
| In carnivores and omnivores, the proximal small intestine recovers at least _____% of total absorbed substances |
|
Definition
|
|
Term
| The remainder of what has not been absorbed by the small intestine of the carnivore/omnivore is absorbed by |
|
Definition
| ileum and large intestine |
|
|
Term
| In herbivores, the proximal small intestine absorbs |
|
Definition
|
|
Term
| The major sites of fluid absorption in herbivores are |
|
Definition
| distal small intestine and large intestine |
|
|
Term
| Bulk water flow is strictly a consequence of osmotic and hydrostatic gradients set up by |
|
Definition
| basolateral membrane Na-K pumps |
|
|
Term
| Where is the site and what is the basic driving force for intestinal secretion of salt and water? |
|
Definition
| Na-ATPase on the basolateral membrane provides a low intracellular Na concentration and negative intracellular electrical potential establishing a large electrochemical gradient for Na diffusion across the apical membrane |
|
|
Term
| How do the mechanisms for Ca absorption differ from those for other electrolytes? |
|
Definition
| does not use Na electrochemical gradient |
|
|
Term
| Since Ca absorption does not use Na in the electrochemical gradient, it facilitates diffusion regulated by Ca binding protein is used to |
|
Definition
| translocate the Ca across the membrane |
|
|
Term
| Ca can be endocytosed or diffused by Ca binding protein, both of which are affected by |
|
Definition
|
|
Term
| How do the SCFAs become undissociated (lipid soluable) in the large intestine lumen? |
|
Definition
| they become undissociated by protonating |
|
|
Term
| SCFAs can become undissociated by protonation by two different sources |
|
Definition
| H+ - hydration of CO2 and apical Na-H exchanger present in the forestomach and proximal colonic epithelium |
|
|
Term
| Name some paracrine mediators that promote intestinal secretion. |
|
Definition
| Prostaglandins, leukotrienes, histamine, serotonin, active oxidants, platelet activating factor, bradykinin, cytokines |
|
|
Term
| What class of systemic hormones mediates intestinal absorption? |
|
Definition
| Epinephrine, coricosteroids, angiotensin, aldosterone, norepinephrine |
|
|
Term
| How does the central nervous system regulate intestinal electrolyte transport? |
|
Definition
| cholenergic agonists decrease absorption of elicit secretion and adrenergic agonists modify cholinergic transmission |
|
|
Term
| Intestinal epithelium is innervated by cholinergic nerves that decreat the action of the _____ absorptive process on the villi and elicit ___ secretion in the crypts. |
|
Definition
|
|
Term
| What is the mechanism of producing diarrhea in association with a rotovirus infection |
|
Definition
| cause diarrhea by causing villous atrophy that leads to maldigestion and malabsorption |
|
|
Term
| What is the mechanism of producing diarrhea in association of enterotoxigenic E. coli? |
|
Definition
| secretes enterotoxins that occupy apical membrane receptors on enterocytes which in turn raise cAMP or cGMP and massive hypersecretion by the intestine |
|
|
Term
| Phagocytes release soluable mediators such as TNF alpha and reactive oxygen metabolites taht are capable of causing epithelial injury causing |
|
Definition
|
|
Term
| Reactive ocygen metabolites can stimulate epithelial secretion directly and also signal ________ cells to secrete ________ that sets off second messengers to cause secretion |
|
Definition
| mesenchymal; prostaglandin |
|
|
Term
| What second messenger in the epithelial cells mediate intestinal secretion? |
|
Definition
|
|
Term
| How is cAMP and Ca ions activated in inflammation? |
|
Definition
| by release of prostaglandins |
|
|
Term
| How are cAMP and Ca ions activated by enterotoxins? |
|
Definition
| binding of receptors to enterotoxins |
|
|
Term
| What is epithelial restitution? |
|
Definition
| immediate response of mucosa to injury and loss of epithelium |
|
|
Term
| How does the process of restitution repair damaged epithelial barrier? |
|
Definition
| viable cells beneath the denuded area are capable of ameboid locomotion and rapidly migrate over the defect, over time increased renewal or proliferation of enterocytes at the base at the base of the crypts to replenish the lost cells |
|
|
Term
| How does proliferation differ from restitution? |
|
Definition
| actual growth and replication of cells vs. initial movement of cell's cytoplasm to cover damaged areas |
|
|
Term
| Why does villous contraction assist the repair process in a damaged epithelium |
|
Definition
| decreases villous height and facilitates restitution by lessening the total surface area for the migrating cells to cover |
|
|
