Why the human heart is described as a "double pump" and what is the physiological significance of this?

The human heart is described as a double pump because blood passes through it and gets pumped out of it twice in a single circuit of the circulatory system. A normal heart is separated into two halves, right and left, between which blood cannot directly pass. Thus, deoxygenated blood from the body enters the right-hand side of the heart and is pumped towards the lungs for oxygenation, before returning to the left-hand side of the heart for pumping to the rest of the body.This is significant because it allows calibration of blood pressure at the lungs and the rest of the body. In a single pump system, blood would be pumped to the lungs and the rest of the body without returning to the heart in-between. The blood pressure required to manage this would be very high, forcing fluid into the alveolar spaces within the lungs and effectively causing drowning. By contrast, in our double pump system, the right-hand side of the heart can pump blood at lower pressure to the nearby lungs, preventing damage, whilst the more muscular left-hand side can force blood around the rest of the body.