Final answer:
Lymphedema can occur after a radical mastectomy due to the disruption of the lymphatic system's ability to manage lymph fluid levels after lymph nodes are removed, leading to localized edema.
Step-by-step explanation:
Lymphedema after a radical mastectomy, where lymph nodes have been removed, might occur due to the disruption in the normal function of the lymphatic system. When lymph nodes are removed, the capacity to regulate lymph fluid levels in the area is compromised, leading to an accumulation of fluid, otherwise known as edema. This is because part of the lymphatic system's role is to collect excess fluid from body tissues and return it to the bloodstream, and the lymph nodes play a crucial role in filtering and directing this fluid. Thus, the answer to the student's question is A: Anything that prevents the normal return of lymph to the blood results in severe localized edema.
Normally, blood pressure causes leakage of fluid from the capillaries, which is then collected by the lymphatic system to prevent swelling. However, when lymphatic vessels or nodes are damaged or removed, the system cannot effectively collect and transport lymph back into the bloodstream. Consequently, fluid builds up in the tissues, leading to lymphedema. Unlike the circulatory system where the heart pumps blood, the lymphatic system relies on the contraction of muscles and lymph vessels themselves to move lymph. Therefore, when nodes are removed, as in the case of a mastectomy, other mechanisms cannot compensate for the loss, and localized edema is likely to occur.