Fats
- Fat digestion and absorption require special handling because many lipid products do not dissolve well in water.
- Pancreatic lipase hydrolyzes fats in the small-intestinal lumen.
- Monoglycerides are lipid digestion products containing one fatty acid attached to glycerol.
- Free fatty acids are fatty acid chains released from triglycerides.
- Glycerol is a small alcohol backbone released during fat digestion.
- Duodenum and upper jejunum absorb most lipid products.
- Bile salts combine with free fatty acids and monoglycerides.
- Micelles are water-soluble clusters that carry lipid products to absorptive-cell surfaces.
- Bile salts have water-friendly and lipid-friendly regions, so they can surround fatty digestion products and help them travel through watery intestinal fluid.
- Micelle formation keeps monoglycerides and free fatty acids close enough to the absorptive-cell surface for uptake.
- Absorptive cells take in micelles and glycerol from the lumen.
- Smooth endoplasmic reticulum resynthesizes monoglycerides and free fatty acids into triglycerides.
- Triglycerides are fats made of glycerol attached to three fatty acids.
- Golgi complex packages triglycerides with proteins to form chylomicrons.
- Chylomicrons are lipoprotein particles that transport absorbed long-chain lipids.
- Exocytosis releases chylomicrons through the lateral cell membrane.
- Basal lamina is crossed by chylomicrons before they enter lacteals.
- Chyle is lymph containing absorbed lipid particles.
- Villus smooth muscle contraction moves chyle into submucosal lymphatic plexuses.
- Thoracic duct is the major lymphatic duct that returns chyle to the bloodstream.
- Left subclavian vein and left internal jugular vein meet where the thoracic duct empties.
- Short-chain fatty acids have fewer than ten to twelve carbon atoms in this context.
- Re-esterified means rebuilt into triglycerides; short-chain fatty acids are not re-esterified.
- Lamina-propria blood vessels receive short-chain fatty acids directly.
- Portal system carries short-chain fatty acids to the liver.
- Route difference is high-yield: many long-chain lipids enter lymph, while short-chain fatty acids enter portal blood.
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