Explain why in human beings oxygenated and deoygenated blood never mix.?

Answer 1

Saying that oxygenated anddeoxygenated blood never mix is a bit misleading. First lets start with the bodies pump, the heart. The heart is divided into four parts, the Left having two parts (L atria and L ventricle) and the Right having two parts (R atria and R ventricle). The Left side of the heart receives oxygenated blood from the lungs first in the L atrium and then into the L ventricle. The L ventricle pumps the blood to the rest of your body through arteries. It is at the level of the capillaries, tiny blood vessels, that oxygenated blood donates it's oxygen to tissue, and hence becomes de-oxygenated. This again is a little misleading because it is not devoid of oxygen, it just has much less oxygen than before the donation. After the donation of oxygen at the capillary the blood is now on the venous side and returns the de-oxygenated blood to the heart. This oxygen poor blood arrives on the R side of the heart in the R atrium and then the R ventricle where it is pumped to the lungs to become oxygenated and then returned to the L atrium and the cycle continues. There are however, disorders of the heart, (ie PDA), that allow de-oxygenated and oxygenated blood to mix in the heart. This leads to poorly oxygenated blood being delivered to tissues.