Britannica
Sources used in this answer
How do valves in lymphatic vessels keep lymph moving in one direction?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
lymphatic system
The human lymphatic system, showing the lymphatic vessels and lymphoid organs.
Valves in the lymphatic vessels function as a mechanical barrier that prevents the backflow of lymph. Because the pressure within these vessels is relatively low and the fluid moves sluggishly, these valves ensure that the fluid continues to travel in a single direction toward the bloodstream.12
The movement of lymph through this system is primarily driven by extrinsic forces, such as the massaging effect of surrounding muscle contractions and other external pressures. As these muscles contract, they push the lymph forward; when the muscles relax, the valves close to stop the fluid from flowing backward, thereby maintaining the necessary one-way circulation.123