Anatomy of the Circulatory System

The human circulatory system, a complex network of cylindrical vessels and a central pump, transports nutrients, gases, and wastes throughout the body via three divisions. Coronary, providing blood to the heart. Pulmonary, including the heart and lungs. And Systemic, to the rest of the body.

When blood leaves the veins of the systemic circuit, it enters the right atrium, an upper chamber of the heart, and then the right ventricle, a lower chamber.

From here, blood travels a short distance into the pulmonary circuit through the pulmonary artery to the lungs where it is oxygenated, and then transported back by the pulmonary vein to the opposite side of the heart, the left atrium. It then flows into the left ventricle, which due to a thicker wall can pump blood much farther through the major artery, the aorta, to the entire body.

The aorta branches off, first to the coronary arteries providing the coronary circuit with blood. And then into other smaller arteries that bring the blood to the systemic circuit. The carotid arteries to the brain. The brachial arteries to the arms. The thoracic arteries to the trunk and gut. And the iliac arteries to the legs.

These arteries divide into even smaller vessels called arterioles and then capillaries going deep into muscles and providing all cells in the body with oxygen and nutrients while removing waste products.

The smallest capillaries converge into venules and veins to return blood. The jugular vein from the brain and head. The superior vena cava from the upper body parts. And the inferior vena cava from the lower body parts. All converge back to the heart and lungs where gas is exchanged and waste is finally removed.