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18 Cards in this Set
- Front
- Back
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Which two enzymes are secreted by the salivary glands? |
-Amylase -Lysozyme |
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Which two enzymes act in the stomach? |
-Pepsin A -Gastric Lipase |
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Which enymes act in the liver? |
-Trypsin -Chymotripsin -Elastase -Carboxypeptidase A -Carboxypeptidase B -Pancreatic Lipase |
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Enzymes of the Brush Border |
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SI Epithelial Cells |
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What does Na+/K+ ATPase do? |
-Creates an electrochemical gradient with low Na+ inside the cell -Array of channel and transporters on lumenal and capillary sides of epithelium, allows Na+/K+ ATPase to drive a range of different transport processes |
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What happens in the large intestine after a current is created by Na+/K+ATPase? |
-Cl- follows the current created by Na+/K+ATPase -Epithelial Na+ channel allows lumenal Na+ ions to flow into cell, creating an electrical potential across the lumenal membrane -Cl- flow into the cell to neutralise potential difference (passive, uncoupled chloride channel) |
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What happens in the small intestine? |
Na+/K+ATPase coupled ti netural Na+ and Cl- transport -Na+ entry coupled to H+ efflux via coupoed Na+/H+ antiport, H+ provided via carbonic anhydrase -Carbonic anhydrase also creates HCO3- ions, creating a gradient which drives Cl- uptake via another antiport |
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What can Na+/K+ATPase also drive? |
NaCl secretion as well as uptake. There are no Na+ channels on the lumenal membrane |
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What is Cystic Fibrosis? |
An autosomal recessive hereditary disease affecting the lungs, sweat glands and the digestive system |
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What is impaired in Cystic Fibrosis sufferers? |
Cl- transport |
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How many Caucasians carry the cystic fibrosis gene? |
1 in every 25 Caucasians carries one CF gene and one normal gene |
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What do cystic fibrosis carries have protection against? |
Cholera (Natural response is for GI eptihelial cells to open their Cl- channels, causing loss of water. CF carries are at reduced risk of dehydration as less fluid is released to clear the bacteria, avoiding diarrhoea. |
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How does Na+/K+ATPase drive NaCl secretion and uptake? |
-There are no Na+ channels on the lumenal membrane -Na+/K+ATPase drives high cellular Cl levels via the Na+/K+/2l- cotransporter (found on capillary membrane) -Cl- flows into lumen via CFTR: -high lumenal Cl- creates electrical potential -draws Na+ into lumen via paracellular route |
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What are bile salts? |
Cholesterol derivatives secreted from the liver |
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Where are bile salts recirculated? |
Between the liver and the intestine -secreted from the liver in the bile; form micelles in small intestine, reabsrobed in distal ileum |
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How much bile is secreted a day? |
20-30g a day, though the total amount in the body at once is only 3-5g. (Bile salts are toxic at high concentrations) |
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What does enterohepatic circulation do, regarding xenobiotics? |
Enterohepatic recirculation delays the elimination of xenobiotics and can increase toxicity |
