The pulmonary circulation takes place from the heart to the lungs and then back to the heart. The systemic circulation takes place from the heart to the body parts and then back to the heart.

The circulatory system is the continuous system of tubes through which the blood is pumped around the body. It supplies the tissues with their nutritional requirements and removes waste products. The pulmonary circulatory system circulates deoxygenated blood from the heart to the lungs via the pulmonary artery and returns it to the heart via the pulmonary vein. The systemic circulatory system circulates oxygenated blood from the heart around the body into the tissues before returning deoxygenated blood to the heart.

In pulmonary circulation, the right atrium receives deoxygenated blood from the superior vena cava, which drains blood from the veins of the upper organs and arms. This deoxygenated blood then passes to the right ventricle, which pumps the blood through the pulmonary arteries to the lungs for re-oxygenation.

Systemic circulation starts in the left atrium when the oxygen-rich blood from the lungs arrives via the pulmonary veins. The blood passes to the left ventricle where it is pumped out through the aorta, the major artery of the body, taking oxygenated blood to the organs and muscles of the body.

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Key Points

• The pulmonary circulatory system circulates deoxygenated blood from the heart to the lungs via the pulmonary artery and returns it to the heart via the pulmonary vein.

• The systemic circulatory system circulates oxygenated blood from the heart around the body into the tissues before returning deoxygenated blood to the heart.

Key Terms

Aorta: the largest artery in the human body which carries the blood from the heart to all parts of the body except the lungs

Vena cava: a large vein that carries deoxygenated blood from the body to the right atrium of the heart

Oxygenated: contains abundant oxygen

Deoxygenated: Contains a lesser amount of oxygen than the amount of carbon dioxide

Pulmonary circulation: the system of arteries and veins that delivers deoxygenated blood to the lungs

Systemic circulation: the system of arteries and veins that carry oxygenated blood to the rest of the body