MICROANATOMY

Detailed explanation-1: -There is no pump in the lymphatic system like the heart in the cardiovascular system. The pressure gradients to move lymph through the vessels come from the skeletal muscle action, respiratory movement, and contraction of smooth muscle in vessel walls.

Detailed explanation-2: -Answer and Explanation: Lymph is returned to the heart through the following mechanisms: Smaller lymphatic vessels contain primary valves, and the larger collecting vessels feature secondary valves. The closely-spaced, one-way valves maintain the lymphatic flow towards the heart and prevent stasis and backflow.

Detailed explanation-3: -Valves are found in larger lymph vessels and collecting vessels and are absent in the lymphatic capillaries. The valves is to prevent backflow of fluid, so that lymph eventually flows forward instead of falling backwards.