The human cardiovascular system has a four-chambered heart that pumps blood through a network of blood vessels using two major circuits called pulmonary and systemic circuits. Oxygen-poor blood pumped out of the heart’s right ventricle travels through the pulmonary circuit. As it passes through the lung, the blood gives off carbon dioxide and binds up oxygen. It then returns to the heart at the left atrium. Oxygen-rich blood pumped out of the left ventricle flows through the systemic circuit. The blood gives up oxygen in capillary beds of the body and re-enters the heart at the right atrium.
Pulmonary circuit mainly composed of pulmonary arteries, which carry blood from the right ventricle to lungs, pulmonary capillaries where the exchange of gas takes place, and pulmonary veins, which carry blood to the left atrium. This circuit starts at the right ventricle and ends at the left atrium. In pulmonary circuit, relatively oxygen-poor and carbon dioxide-rich blood returning from the body enters the right atrium and passes into the right ventricle, which pumps it to the lungs via the pulmonary trunk. The main two functions of pulmonary circuit are to deliver the blood to the lungs so that it can enrich with oxygen and to help the body get rid of carbon dioxide.
The systemic circuit supplies blood to the capillary beds in all parts of the body that are not served by the pulmonary circuit. In this circuit, oxygenated blood pumped by the left half of the heart circulates through the body and returns to the right atrium. The circuit starts when left atrium receives blood from the pulmonary veins. At any moment, systemic circuit contains about 84% of the total blood volume and begins at the left ventricle and ends at the right atrium.
What is the difference between Pulmonary Circuit and Systemic Circuit?
• The circuit through which blood flows from the heart to lungs and back is called pulmonary circuit, whereas the circuit through which blood flows from the heart to body tissues and back is called systemic circuit.
• When compared with the systemic circuit, pulmonary circuit is short; the lungs and pulmonary trunk are about 6 inches apart.
• The arteries of pulmonary circuit carry deoxygenated blood, whereas that of systemic circuit carry oxygenated blood.
• The right side of the heart is pulmonary circuit pump, and the left side of the heart is systemic circuit pump.
• Pulmonary circuit receives blood from body tissues and circulates it through lungs, whereas systemic circuit receives blood from pulmonary veins and pumps to the aorta, which spreads the oxygenated blood thought out the body.
• Pulmonary circuit’s components are found mainly in the abdominal cavity, associated with lungs, whereas systemic circuit’s components are found in all over the body.