Thousands of villi project into the lumen of the small intestine per square inch of mucosal surface. Within each villus are capillaries and a lymphatic vessel. Much of the absorption occurs by active transport, mainly sodium-dependent co-transport. Nutrients transported into the capillaries pass to the hepatic portal vein on the way to the liver. Triglycerides are broken down in the intestine and pass through the intestinal wall, coated with phosphoproteins, to form chylomicrons, then passed into the lymphatic vessels, which are called lacteals.