Final answer:
The Inguinal lymph nodes drain the legs, external genitalia, lower abdomen, and buttocks, and are part of the larger lymphatic system, including the thoracic duct.
Step-by-step explanation:
The lymph nodes that drain the legs, external genitalia, lower abdomen, and buttocks are the Inguinal lymph nodes. These nodes are located inferior to the umbilical region and are responsible for draining the lymph from the mentioned regions, which includes structures that are inferior to the gluteal region and generally areas that are superior to the popliteal region.
The thoracic duct is a large duct that receives lymph from the lower limbs, the left thorax, the left upper limb, and the left side of the head, and along with the right lymphatic duct, plays a critical role in directing lymph back into the bloodstream.