Why is the human circulation called a double circulation?

Answer 1

With a double circulatory system, the heart can increase the pressure of the blood after the blood has picked up oxygen from the lungs. This means it can transport oxygen to the body tissues much quicker.

Answer 2

double circulation means blood flows through the heart twice. first circulation is completed when deoxygenated blood is brought to heart and is further pumped to lung for oxygenation. the second circulation pathway is from lungs to heart and then back to the body. so double circulation is important as it helps in oxygenation of blood.

Answer 3

Double circulation allows for a pressure increase after gas exchange occurs.

In single circulation, the blood goes from the heart to the gill capillaries. Since these are so thin the starting pressure must be low so the capillary membranes don't leak. This causes less perfusion of gases into the tissues after the blood leaves the gills.

Evolution solved this problem through double circulation, which began with lungfish. They have a partially divided heart which seperates the pulmonary and systemic circuit, so after the blood is replenished with oxygen it comes back to the heart which gives it a second pump so it has a higher pressure when it reaches the body.

Humans have a fully divided circulation. Unlike partially divided systems, in humans the blood doesnt mix in the heart and it doesnt require "shunting" from one side of the heart to the other like lungfish do. It goes from Right ventricle->pulmonary artery->to the lungs-> pulmonary vein-> left atrium-> left ventricle->systemic circulation-> right atrium etc.

This means there is a higher pressure difference between the systemic and pulmonary circuits, therefore, better perfusion and blood flow in the body.

Answer 4

The blood passes through the heart twice