Final answer:
The thoracic duct is the lymphatic trunk that drains the legs and pelvic cavity, receiving lymph from lumbar trunks and the intestinal trunk, and draining into the left subclavian vein. The femoral vein drains the legs and becomes the external iliac vein, which leads into the common iliac vein. The ascending lumbar veins drain the lumbar regions into the azygos or hemiazygos veins.
Step-by-step explanation:
The lymphatic trunk that drains the legs and pelvic cavity is known as the thoracic duct. This large lymphatic vessel receives lymph from the lower abdomen, pelvis, and lower limbs through the left and right lumbar trunks and the intestinal trunk.
The thoracic duct begins just beneath the diaphragm in the cisterna chyli and ultimately drains into the left subclavian vein. The internal iliac vein also plays a role in this drainage process, gathering blood from the pelvic organs and integument before leading to the common iliac vein. Additionally, the femoral vein is responsible for draining blood from the legs.
As the femoral vein ascends into the body cavity, it becomes the external iliac vein, which then meets the internal iliac vein to form the common iliac vein. Venous drainage from the upper leg is also facilitated by the femoral vein, as it receives blood from the great saphenous vein, the deep femoral vein, and the femoral circumflex vein.
Further, the ascending lumbar veins drain the lumbar portion of the abdominal wall and spinal cord into the azygos vein on the right or the hemiazygos vein on the left, with the remaining lumbar veins draining directly into the inferior vena cava.