What is the main purpose of the lymphatic ducts?

The primary function of the lymphatic ducts is to drain lymph, a clear fluid that contains white blood cells, excess tissue fluid, and waste products, back into the bloodstream. This process is essential for maintaining fluid balance in the body and for the proper functioning of the immune system. By collecting and transporting lymph from peripheral tissues, the lymphatic ducts ensure that this fluid does not accumulate and cause edema. Additionally, by returning lymph to the circulation, the ducts facilitate the distribution of immune cells and other substances throughout the body, enhancing the immune response.

The other options mention functions unrelated to the lymphatic system. Producing red blood cells is a function of the bone marrow, delivering oxygen to tissues is the role of the circulatory system via red blood cells, and filtering blood is performed by the spleen rather than the lymphatic ducts. The focus of the lymphatic ducts is specifically on lymph drainage and immune support, making the correct option essential to understanding their role in maintaining homeostasis in the body.