What component do lymph vessels have that veins also possess?

Lymph vessels share a critical feature with veins, which is the presence of valves. These valves play a vital role in preventing the backflow of lymph fluid, similar to how they function in veins to prevent blood from flowing backward due to gravity or changes in body position. The presence of valves is essential in maintaining unidirectional flow in both systems, ensuring that lymph and blood return to the heart effectively.

Unlike veins, lymph vessels do not typically have thick walls or a significant amount of smooth muscle. Instead, lymph vessels are generally thinner-walled and more flexible, which allows them to accommodate varying volumes of lymphatic fluid. Thus, while they may contain some smooth muscle, it is not a defining feature that they have in common with veins, unlike the important function that valves serve in both types of vessels.