posterior thoracic cavity around the respective intercostal space parietal pleura deep to the intercostal space Individual nodes on each side are sited just lateral to the head of the respective rib, deep to the innermost intercostal muscles. They receive efferent lymphatic vessels running around the intercostal space and emerging from between the muscles or from their deep surface.
There may be one or two nodes in every intercostal space, and they link up to each other by a lymphatic channel that runs inferiorly to superiorly. The posterior intercostal chain may drain:
for superior intercostal spaces to: on the left, the thoracic duct: directly, above the arch of the aorta indirectly, via posterior mediastinal lymph nodes on the right, the right lymphatic duct in the lower intercostal spaces, to a descending intercostal trunk that eventually joins to the cisterna chyli below the diaphragm
One or two small nodes located posteriorly in each intercostal space; they receive lymph from the parietal pleura, intercostal space, and posterior body wall; the nodes in the upper spaces empty into the thoracic duct; the nodes in the lower spaces form a descending intercostal trunk that opens into the cisterna chyli.