Which structures in the lymph vessels ensure that lymph flows in one direction? valves lymph nodes ducts lymphocytes

Option A,  Valves

Explanation:

Lymphatic vessels are valved structures as they carry thin walled valves in it. Valves allow one way movement of lymph fluid. As the pressure inside a lymphangion increases, the semilunar valve opens and allows the movement of lymph fluid  into another lymphangion. This semilunar valve prevents the backward flow of the lymph fluid and thus a lymphatic system requires no central pump to operate efficiently.

the denominator has a very specific role.

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