Thoracic duct

This lymphatic vessel commences at the upper end of the cisterna chyli, on a level with the body of T12 vertebra between the aorta and the azygous vein. From behind the right crus it passes upwards to the right of the aorta and comes to lie against the right side of the esophagus. Inclining up to the left, alongside the aorta, it passes behind the esophagus to reach its left side at the superior mediastinum. It lies anterior to the inter­costal branches of the aorta. Passing now vertically upwards it finally arches forwards across the dome of the left pleura to enter the point of confluence of the left internal jugular and subclavian veins. It normally divides into two or three separate branches, all of which open at the angle between these two veins. There are no valves at the termination, and blood flows to and fro in the duct as pressures alter with respiratory movements. At autopsy it is common to find the terminal inch or two of the thoracic duct full of blood, because the last of the valves, of which there are many, is a little proximal to the venous junction. Commencing with the accumulated lymph from the lower half of the body, the duct receives in its course through the thorax lymph from the left posterior intercostal nodes (posterior half of the left thoracic wall). In the neck it receives the left jugular and subclavian lymph trunks and thus finally comes to drain all the lymph of the body except that from the right arm and the right halves of thorax and the head and neck.

Lymph from the posterior right thoracic wall enters the right lymphatic duct. The right upper limb drains into the right subclavian trunk and the right side of the head and neck drains into the right jugular lymph trunk. These three trunks may join together and open into the commencement of the right brachiocephalic vein or they may remain separated and open independ­ently into the great veins (jugular and subclavian).