your skin of course!
a flap of tissue that prevants blood from flowing backward is
Heart valve.
valves in the veins
heart valves
the valves
valve
Venous valves .
valve
Venous valves .
Valves. Mitral and aortic.
Venous valves .
Blood is a constant whereabout in our bodies. As of such a frequent heartbeat exists within our system. Which causes the blood within our bodies to flow forward, in lamense terms it produces a very large push for the blood to distribute it's nutrients throughout the body and back within our heart and out again. This constant push is what prevents blood from flowing backwards in your veins.