lymphatic vessels [L, lympha, water, vascellum, little vase] , fine, thin-walled, transparent valved channels distributed through most tissues. They are often distinguished by their beaded appearance, which is caused by an irregular lumen. The collecting branches form two systems, one generally running with the superficial veins and the other below the deep fascia and including the intestinal lacteals. Lymphatics resemble veins but have more valves, have thinner walls, and contain lymph nodes. They drain through a thoracic duct and a right lymphatic duct into the venous system near the base of the neck. They include three layers: intima, media, and adventitia.
