How does blood circulate between the heart and the lungs?

Blood circulates between the heart and the lungs through a process called pulmonary circulation. Here's how it works:

• Deoxygenated blood: Deoxygenated blood from the body returns to the right atrium of the heart through two large veins called the superior vena cava and the inferior vena cava. The right atrium then contracts, forcing the blood through the tricuspid valve into the right ventricle.

• Pulmonary artery: From the right ventricle, the deoxygenated blood is pumped out of the heart through the pulmonary artery, which carries it to the lungs.

• Oxygenation in the lungs: In the lungs, the blood vessels branch into smaller vessels called capillaries, which surround the air sacs (alveoli). Here, carbon dioxide is released from the blood into the alveoli, and oxygen from the inhaled air diffuses into the blood, oxygenating it.

• Pulmonary veins: Oxygenated blood returns from the lungs to the heart via the pulmonary veins, which carry it to the left atrium of the heart.

• Systemic circulation: From the left atrium, the oxygenated blood is pumped into the left ventricle and then out of the heart through the aorta, which distributes it to the rest of the body, providing oxygen and nutrients to the cells.

This continuous cycle of circulation ensures that oxygen-rich blood is supplied to the body's tissues while carbon dioxide and other waste products are removed through the lungs.