How does lymph fluid flow through the lymphatic system?

Lymph fluid flows through the lymphatic system primarily due to the contractions of surrounding muscles, particularly skeletal muscles. As these muscles contract during physical activity, they squeeze the lymphatic vessels, which helps propel the lymph fluid forward. This movement is crucial because lymph fluid does not have a central pump like the circulatory system's heart to assist in its flow. Additionally, the lymphatic vessels have one-way valves that prevent backflow, ensuring that lymph fluid moves in a unidirectional manner towards the lymph nodes and ultimately back into the bloodstream. This mechanism is essential for maintaining fluid balance in the body and for the immune response, as lymph fluid transports immune cells to areas of infection or inflammation.

In contrast, lymph fluid is not moved passively solely by gravity, nor is it pumped by the heart. It also does not flow directly due to the pressure in blood vessels; rather, the lymphatic system is an independent system that relies on the actions of muscles and the structure of lymphatic vessels.