The circulatory system consist of two circular systems of tubes, circulation through the lungs (pulmonary circulation) and circulation through the rest of the body.
Every blood system of circulation requires three characteristics:
*A pump – contractile
*A system of channels or tubes – blood vessels
*A fluid medium – blood
The blood flow in the closed vascular system is maintain by the pumping action of the heart. Blood is moved though these systems by two pumps, the right and left sides of the heart. It is enclosed in a tough membranous sac called the pericardium.
Although these right and left pumps beat together, the blood in each side is entirely separate, and the two pumps can and do to some extent, function independently. In one day the heart moves more than 700 liters of blood through the body. This is done by means of the rhythmic pumping action of the heart.
Because pushing blood through the lungs is much easier than pushing it though every part of the body, the left side of the heart is bigger, more muscular and carries a much heavier workload that the right.
Oxygen enriched blood from the lungs returns through the pulmonary veins to the left atrium. From the left atrium it enters the left ventricles, which pumps the blood through the aorta into the system circulation.
Vascular blood system
