18 Feb 2016 | 258,249 Views. You may not even associate this with your health, yet it can make a life or death difference. Ignore or defy it, and your risk of death before your 65th birthday jumps 25 percent. Here's the big takeaway message to tell your body for health and longevity.
1 Veins have valves which maintain the unidirectional flow of blood, even against gravity. 2  Since the venous pressure is low (7 mm Hg) the valves are of utmost value in the venous return. However, the valves are absent in: 3  The veins of less than 2 mm diameter.  The venae cavae.
How the Heart Valves Work. At the start of each heartbeat, blood returning from the body and lungs fills the atria (the heart's two upper chambers). The mitral and tricuspid valves are located at the bottom of these chambers. As the blood builds up in the atria, these valves open to allow blood to flow into the ventricles (the heart's two lower chambers). After a brief delay, as the ventricles begin to contract, the mitral and tricuspid valves shut tightly.