The lymphatic system, lymph vessels and lymph nodes.
NIH
2013-11-05 04:14:28
NIH (a US government agency) image, <a rel="nofollow" class="external autonumber" href="https://www.cancer.gov/images/Documents/6b08d7cc-2a8f-4d32-9a38-a5433aaf0794/lymph.gif">[1]</a> (recreated as a vector image; see <a href="//commons.wikimedia.org/wiki/Commons:Media_for_cleanup" title="Commons:Media for cleanup">Commons:Media for cleanup</a>)