PATHOLOGY

Detailed explanation-1: -Veins have valves to prevent the backflow of blood because the blood in veins flow .

Detailed explanation-2: -Medium and large veins have venous valves, similar to the semilunar valves associated with the heart, that help keep the blood flowing toward the heart. Venous valves are especially important in the arms and legs, where they prevent the backflow of blood in response to the pull of gravity.

Detailed explanation-3: -The one-way valves in deep veins prevent blood from flowing backward. The muscles surrounding the deep veins squeeze the veins, helping force the blood toward the heart, just as squeezing a toothpaste tube ejects toothpaste.