Sorry this is Anatomy. Please help.
Veins returning to the heart can close to prevent the backflow of blood. Which component in the veins contributes to this process?
connective tissue in the tunica media
smooth muscle in the tunica media
endothelium in the tunica intima
movable valves in the tunica intima

Question

Sorry this is Anatomy. Please help.
Veins returning to the heart can close to prevent the backflow of blood. Which component in the veins contributes to this process?  
connective tissue in the tunica media
smooth muscle in the tunica media
endothelium in the tunica intima
movable valves in the tunica intima

kyanthedoodle · Answer

I think I know what it is.

anonymous · Answer

What tissue relaxes and contracts every time you move?

kyanthedoodle · Answer

Wait. I'm confused.

javk · Answer

there are valves in the veins that prevent backflow.