lacteals

Lacteals are the lymphatic capillaries located in the lamina propria of the small intestine’s villi. They form part of the lymphatic system and are specialized for the absorption and transport of dietary lipids absorbed from the gut lumen.

Structurally, each villus contains a blind-ended lacteal lined by endothelial cells with relatively loose intercellular junctions. These junctions permit uptake of lipid-rich chyle from the intestinal lumen. Anchoring filaments connect lacteals to the surrounding tissue, helping to maintain their patency amid gut movement, and the lacteals drain into larger mesenteric lymphatic vessels.

Functionally, lacteals collect long-chain fatty acids that are packaged into chylomicrons by enterocytes. The chylomicron-containing fluid enters the lacteal and is carried via the mesenteric lymphatic network to the cisterna chyli and then the thoracic duct, ultimately emptying into the venous circulation at the left subclavian vein. Short- and medium-chain fatty acids, in contrast, are absorbed directly into the portal blood and bypass the lacteals.

Lacteals also contribute to gut immunity as part of gut-associated lymphoid tissue, participating in immune surveillance by sampling luminal antigens and interacting with immune cells. Clinically, dysfunction or dilation of intestinal lymphatics, such as in intestinal lymphangiectasia, can lead to protein-losing enteropathy. Inflammatory or other diseases can alter lacteal permeability and fat absorption, contributing to malabsorption syndromes.