<P> Veins are less muscular than arteries and are often closer to the skin . There are valves in most veins to prevent backflow . </P>
<P> Veins are less muscular than arteries and are often closer to the skin . There are valves in most veins to prevent backflow . </P>
why is it important for veins to have valves
why is it important for veins to have valves
to prevent backflow
to prevent backflow