Lacteals

Lacteals are specialized lymphatic capillaries located within the villi of the small intestine. Intestinal villi contain blood capillaries and typically a central lacteal. Like other initial lymphatic vessels, lacteals collect fluid and material from surrounding tissue, but they are particularly important for transporting absorbed dietary lipids .¹

After dietary fats are digested, their products are taken up by enterocytes, the absorptive cells lining the intestinal villi. Inside enterocytes, many absorbed long-chain fatty acids and monoacylglycerols are reassembled into triglycerides and packaged into lipoprotein particles called chylomicrons. These particles are released from the enterocytes and enter the lacteals within the villi .^1,2

Once inside a lacteal, chylomicrons are carried with lymph into progressively larger intestinal and mesenteric lymphatic vessels. The lymph eventually reaches the thoracic duct, which empties into the venous circulation. This route allows much of the dietary fat carried in chylomicrons to reach the systemic bloodstream without first passing through the hepatic portal circulation .^1,2

Lacteals are distinct from the blood capillaries that also occupy intestinal villi. Many water-soluble nutrients enter these blood vessels and travel toward the liver through the portal circulation, whereas chylomicron-associated lipids primarily enter the lymphatic system through lacteals. The specialized endothelial structure of lacteals facilitates chylomicron uptake, although the exact mechanisms by which these large particles enter remain an area of study .^1,2