The large lymphatic vessels empty into veins. The vessels start with capillaries. The lymphatic system is composed of supervical and deep lymphatic vessels with many lymphatic nodes scattered throughout the body. The lymphatic vessels are thinner-walled than the veins. They do not have anastomoses except through lymphatic nodes.
All lymphatic vessels have valves.
The lymphatic nodes interposed in the lymphatic system have the function of counteracting and destroying poison. Most of the lymph traverses some nodes before entering the veins. The largest lymphatic nodes are only about three centimeters in diameter. Quite large lymphatic stems are found on each side of the head and neck and in the abdominal viscera, into which the lymph is gathered and emptied into the veins of the lower neck or upper thorax. There are seven large lymphatic stems, three of which unite to form the thoracic duct which also receives two other stems.