Final answer:
The lymphatic system's function that ensures tissues are not damaged due to excess fluid is lymphatic drainage, which collects and returns the excess tissue fluid to the bloodstream, thus preventing lymphedema.
Step-by-step explanation:
The lymphatic system has several essential functions, including the critical role of maintaining fluid balance in the body's tissues. One of its key functions is to perform lymphatic drainage, which is the answer to the question of which function ensures that tissues are not damaged due to the accumulation of excess fluid. This system achieves this by collecting excess tissue fluid—fluid that isn't reabsorbed by the vascular capillaries—and returning it back to the bloodstream, thereby preventing the potential harm that could come from fluid accumulation, such as lymphedema.
Apart from lymphatic drainage, the lymphatic system is an integral part of the immune system, responsible for the production and transport of lymphocytes and antibodies throughout the body. It also has roles in nutrient absorption, specifically the transport of dietary lipids from the digestive system into the bloodstream.