How are triglycerides rebuilt inside cells lining the small intestine?

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A composite diagram shows the structural formulas, space-filling models, and simplified depictions of lipid molecules including stearic acid and phosphatidylcholine, and how these assemble into a micelle and lipid bilayer, with labels identifying hydrophilic heads and hydrophobic tails. — Lipid Structure and properties of two representative lipids. Both stearic acid (a fatty acid) and phosphatidylcholine (a phospholipid) are composed of chemical groups that form polar “heads” and nonpolar “tails.” The polar heads are hydrophilic, or soluble in water, whereas the nonpolar tails are hydrophobic, or insoluble in water. Lipid molecules of this composition spontaneously form aggregate structures such as micelles and lipid bilayers, with their hydrophilic ends oriented toward the watery medium and their hydrophobic ends shielded from the water.

Once micelles transport fatty acids and monoglycerides into the cells lining the small intestine, the bile salts diffuse back into the intestinal lumen. A carrier protein then transports the fatty acids and monoglycerides to the endoplasmic reticulum within the cell interior.1

At this site, the triglyceride is synthesized again through the action of an enzyme catalyst known as acyltransferase. Following this, the newly formed triglycerides are moved to the Golgi apparatus, where they are packaged into chylomicrons—vesicles coated with phospholipids and apoprotein—for transport into the lymphatic system.1