Question

why is important for our heart to keep oxygen-rich blood separate from oxygen poor blood

Answer 1

It is necessary for our heart to separate oxygenated and de-oxygenated blood because this makes their circulatory system is more efficient and helps in maintaining constant body temperature.If this would not be done then there would be less oxygen supply to the cells, under oxygen deficient condition cells will not function normally and may not perform the activities normally.If the two were mixed together without any separation, then our body mechanism of quickly removing acidic substances and maintaining a steady supply of oxygen throughout the body would be very very slow, if not at all efficient.

Answer 2

if the oxygenated and deoxygenated blood are mixed together, it lead to large increase in blood volume that goes back to the lungs.