As for the direction and distribution of the nutrient blood vessels in the human thoracic duct wall, the arterioles and venula that have branched out from the main branches of the tunica adventitia enter into the tunica media in the same ascending angle as smooth muscle cells of the exterior layer of the tunica adventitia. The artery that has entered into the tunica media, runs obliquely in an arch line while sending out a few branches on its way before reaching the tunica intima. On the exterior surface of the internal elastic membrane, these branches quickly connect with each other to form a marked capillary networks all over the outer surface of the internal elastic membrane. In a rare instance, some branches from such capillary network are distributed in the subendothelial layer through the network of the internal elastic membrane. The running way of capillary venule group originating from the above-mentioned capillary network is the same as the arterioles originating from the artery.