Final answer:
Oxygen-poor blood passes through the pulmonary circulation, moving from the right atrium to the right ventricle, and from there to the lungs for oxygenation. Once oxygenated, it returns to the heart's left atrium via the pulmonary veins. This is followed by systemic circulation which distributes oxygen-rich blood throughout the body and returns the deoxygenated blood to the heart.
Step-by-step explanation:
Oxygen-poor blood passes through the pulmonary circulation.
The right atrium receives oxygen-poor blood from the body. This blood then flows to the right ventricle, which pumps it toward the lungs via the pulmonary arteries. Here, the blood gets oxygenated, releasing carbon dioxide and picking up oxygen in the process. After oxygenation, the blood, now rich in oxygen, leaves the lungs through the pulmonary veins and returns to the left atrium of the heart, completing the pulmonary cycle.
Following this, systemic circulation begins as the left ventricle pumps the oxygen-rich blood out of the heart via the aorta, distributing it to various parts of the body through arteries and capillaries. The now deoxygenated blood, having delivered oxygen to the body's tissues, returns to the heart through the veins, primarily through the superior vena cava and the inferior vena cava, and enters the right atrium, beginning the cycle anew. The systemic circulation is vital as it supplies oxygenated blood to the body's organs and tissues and brings back oxygen-poor blood to the heart for reoxygenation.