2.63 describe the structure of the heart and how it functions

 The heart consists of 4 main areas, the left and right side are separated by a wall of muscle called the septum. There is a left and right atrium which is where the blood first goes when it enters the heart. After passing through the atrium the blood will enter the ventricle where it will then be pushed out of the heart.

Deoxygenated blood comes in from the vena cava and enters the right atrium, passes through the tricuspid valve and into the right ventricle. The blood then passes through the semilunar valve and out of the heart into the lungs via the pulmonary artery. Once the blood is oxygenated is re enters the heart through the pulmonary vein, into the left atrium, then left ventricle before being brought to the rest of the body from the aorta (brain, liver, kidneys digestive system etc.)

Double circulation: the majority of mammals have double circulation (one circuit connects the heart and lungs; the other circuit links the heart with the body) this is important because it ensures that the blood flowing to the cells is full of oxygen: it makes it more efficient.