7 Why is there no passage between the left and right Ventricle?

Because we have what is called a double-circulation system. The right and left side of the heart send blood to different areas of the body, and the blood must be kept separate. The right side sends deoxygenated blood from the body to the lungs to be oxygenated. The left side sends oxygenated blood from the lungs to the body. If there were a passage between the left and right ventricles, then a couple of things could happen. Some deoxygenated blood from the body would be recirculated to the body, decreasing the oxygen supply for the body's cells. Also, some oxygenated blood from the lungs would be re-circulated back through the lungs. It would make for a much less efficient system for oxygenating the body and ridding the body of carbon dioxide. ANy such opening would likely be surgically closed if at all possible.