The heart pumps blood around in the body and is thus the most important muscle in the body.
The heart consists of two halves that each consists of an atrium and a ventricle. The left ventricle pumps blood out into the entire body through arteries. When the blood has provided oxygen to the cells in the body, the blood will then run back to the right half of the heart through the veins. From there the blood will be pumped into the lungs for oxygenation.
The heart valves control the bloodstream through the heart and direct the bloodstream the right way around the body.
The coronary artieries, which are on the outside of the heart, provide blood for the heart.
The pumping efficiency of the heart is controlled by the electrical system of the heart and start in the right atrium. The heart contracts when the electric impulses strike the heart muscle cells, and a pulse beat has begun. The electric impulses are then sent down through the heart into the ventricles, and from there the blood is pressed out into circulation. The contraction of the heart thus happens in two stages.