thoracic duct, the common trunk of all the lymphatic vessels in the body, except those on the right and left sides of the head, the neck, and the thorax; the upper abdominal wall; the right and left upper limbs; the right and left lungs; the right side of the heart; and the diaphragmatic surface of the liver. In the adult it is 38 to 45 cm long and 3 to 5 mm in diameter. Also called alimentary duct. Compare right lymphatic duct. See also lymphatic system.
