What Is Systemic Circulation?

The heart is the chief organ of circulation of the blood.  The course of the blood from the left ventricle through the arteries, arterioles and capillaries, returning it to the right atrium by the veins is called the greater of systemic circulation.

SYSTEMIC CIRCULATION
The blood leaves the left ventricle of the heart by the aorta, the largest artery in the body.  This breaks up into smaller arteries which carry the blood to the different parts of the body.  These divide and subdivide until the arterioles are reached.  These have very muscular walls which narrow their channels and resist the flow of blood.  This has two functions:  it maintains the arterial blood pressure and --- by varying the size of the channel --- it regulates the flow of the blood into the capillaries.  The capillaries have very thin walls so that exchange can take place between the plasma and the interstitial fluid.  These capillaries then unite and form larger vessels called venules which in turn become veins, and carry the blood back to the heart.  The veins unite and unite again until finally two large venous trunks are formed, the inferior vena cava which collects blood from the trunk and lower extremities and the superior vena cava which collects blood from the head and upper extremities.  Both these vessels empty their contents into the right atrium of the heart.

The left ventricle pumps the oxygenated blood into the systematic aorta.It gives off arteries to all the organs of the body except the lungs.These arteries breaks up into capillaries on reaching their respective organs.Here the blood becomes deoxygenated by distributing oxygen to the tissue cells.The deoxygenated blood from the visceral capillaries is brought to the right atrium by superior and inferior venacava.This course of blood from left ventricle to the right atrium of heart via body tissues is called systematic circulation.