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Questions and Answers
What is the primary consequence of abnormalities in the preparatory and transport phases of lipid absorption?
Which condition is NOT listed as a cause of bile flow obstruction?
Which of these phases are involved in lipid digestion and absorption?
What is tropical sprue associated with?
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What is the normal percentage of ingested fat excreted in feces?
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What stimulates the secretion of electrolytes and fluid components of pancreatic juice?
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What causes the contraction of the gallbladder?
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Which of the following does NOT directly stimulate the secretion of pancreatic juice?
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What stimulates the secretion of the pancreatic enzymes?
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What is the role of acid chyme in the small intestine?
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Which enzyme breaks down triglycerides into monoglycerides and fatty acids?
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What does Phospholipase A2 break down phospholipids into?
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How are short-chain fatty acids absorbed?
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What is the fate of long-chain fatty acids during absorption?
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Where does free glycerol taken after being released in the intestinal lumen?
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Study Notes
Digestion of Lipids
Digestion in Small Intestine
- Pancreatic juice contains lipolytic enzymes that break down lipids:
- Lipase breaks down triglycerides into monoglycerides and fatty acids
- Phospholipase A2 breaks down phospholipids into lysolecithin and fatty acids
- Cholesterol esterase breaks down cholesterol esters into cholesterol and fatty acids
Stimulation of Pancreatic Juice Secretion
- Acidic gastric contents (acid chyme) entering the duodenum stimulate pancreatic juice secretion
- GI hormones also stimulate secretion:
- Secretin increases secretion of electrolytes and fluid components
- Pancreozymin (CCK-PZ) stimulates secretion of pancreatic enzymes
- Cholecystokinin (CCK-PZ) causes gallbladder contraction and bile discharge into the duodenum
Absorption of Lipids
- Glycerol is absorbed directly into the portal vein and taken to the liver
- Fatty acid absorption varies based on carbon content:
- Short-chain, medium-chain, and unsaturated FAs are absorbed into portal blood and taken to the liver
- Long-chain FAs are absorbed, re-esterified into TG, and enter the lymphatic system
Clinical Significance
- Steatorrhoea occurs due to abnormalities in lipid digestion and absorption:
- Biliary obstruction
- Pancreatic diseases
- Tropical sprue (abnormal villi and inflammation of the lining epithelium)
- Normally, less than 0.5% of ingested fat is excreted in feces
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Description
This quiz covers the digestion of lipids in the small intestine, including the role of pancreatic juice lipolytic enzymes, and the absorption of lipids.
