Lacteais

Lacteais is the term used for the lacteal lymphatic vessels found in the small intestine, part of the mucosal lymphatic system. These vessels are located within the lamina propria of the intestinal villi and consist of thin-walled, blind-ended lymphatic capillaries. Their endothelial lining forms primary valves by overlapping cells, which helps regulate lymph flow as chyle moves toward larger lymphatic channels.

Lacteais drain into the intestinal lymphatic trunks, which converge into the cisterna chyli and eventually the thoracic duct. They are most prominent in regions of the small intestine where fat absorption is active, with a distribution that reflects the need to transport absorbed lipids from the gut.

Functionally, lacteals absorb dietary fats in the form of chyle. Long-chain fatty acids are reassembled into triglycerides within enterocytes and packaged into chylomicrons, which enter the lacteals and travel through the lymphatic system. Short- and medium-chain fatty acids, and other nutrients, are typically absorbed directly into the portal venous blood. The lymphatic route allows fats to bypass the liver initially and enter systemic circulation as chyle.

Clinical relevance includes conditions that affect intestinal lymphatics, such as intestinal lymphangiectasia, which can cause protein-losing enteropathy and edema. Obstruction or rupture of the lacteals or surrounding lymphatics can lead to chylothorax or other forms of lymphatic disruption. Inflammatory or infectious processes may indirectly impair lacteal function by damaging villous architecture.

Etymology derives from Latin lacteus, milky, reflecting the milky appearance of chyle carried by these vessels.