How is the lymphatic system dependent on the circulatory system?

The lymphatic system is dependent on the circulatory system primarily because it drains into it. The lymphatic system collects excess interstitial fluid, which is fluid that bathes the cells in tissues and is not absorbed into the capillaries of the circulatory system. This collected fluid, known as lymph, ultimately returns to the bloodstream through the lymphatic vessels that merge with the circulatory system at specific points, particularly at the subclavian veins. This drainage is crucial for maintaining fluid balance in the body, supporting the immune response, and enabling the transportation of dietary lipids.

While the other choices reference functions that are important in their own right, they do not highlight the direct relationship of the lymphatic system to the circulatory system as well as the correct option does. For instance, the lymphatic system does not produce red blood cells or circulate hormones directly. While it does help in nutrient absorption by transporting fats and fat-soluble vitamins from the digestive system, this function is secondary to its role of draining lymph back into the circulatory system. Thus, the interdependence is best demonstrated by the drainage of lymph into the circulatory system.