Veins returning to the heart can close to prevent the backflow of blood. which component in the veins contributes to this process? a. connective tissue in the tunica media b. smooth muscle in the tunica media c. endothelium in the tunica intima d. movable valves in the tunica intima

The correct answer is option d.

Explanation:

Veins are the blood vessels which carry blood back to the heart. These are less muscular as compared to the arteries. The prevent back flow of the blood with the help of valves.

Valve is a membranous structure which allow the flow of blood in one direction only. They can fold or close in one direction only.

For example, with each pump or contraction when blood flows towards the heart the valves open. However, they close immediately which prevent the back flow.

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explanation: