Circulatory System Learning Path

Heart chambers and pumping roles

The heart contains four chambers—right atrium, right ventricle, left atrium, and left ventricle—that work together to pump blood through two main circuits: pulmonary and systemic circulation. The pulmonary circuit moves oxygen-poor blood from the right heart to the lungs for gas exchange, then returns oxygen-rich blood to the left atrium. The systemic circuit sends oxygen-rich blood from the left heart to the rest of the body and returns oxygen-poor blood to the right heart via the large veins (superior and inferior vena cava). In the pulmonary pathway, blood enters the right atrium from the venae cavae, passes through the tricuspid valve into the right ventricle, and is pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs. After oxygen is absorbed and carbon dioxide is released in the lungs, oxygen-rich blood returns through the pulmonary veins to the left atrium. In the systemic pathway, oxygenated blood leaves the left ventricle through the aortic semilunar valve into the aorta, supplying tissues throughout the body before returning to the right atrium through the venae cavae, completing the loop.

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Pulmonary circulation pathway

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