Thoracic duct, << thaw RAS ihk, thoh RAS ihk, or thuh RAS ihk, >> is the largest vessel of the lymphatic system, a network of tubes that returns fluid from body tissues to the bloodstream. The thoracic duct passes through the thoracic cavity, which lies in front of the spinal column. The duct empties a clear fluid called lymph and a milky-white fluid called chyle into the bloodstream through the left subclavian vein, a large vein lying under the collarbone. Eventually lymph from all but the upper right quarter of the body reaches the thoracic duct.
Lymph is a nearly colorless liquid in the tissues of the body, somewhat like blood without the red blood cells. Lymph is derived from parts of the blood that have filtered through capillary walls. Chyle is a milky liquid composed of lymph and digested fats, formed from the chyme (partially digested food) in the small intestine. The chyle travels from the small intestine into the veins, chiefly by means of the intestinal lymphatic vessels.
See also Lymphatic system .
