Figure 18.13: The right side of the heart pumps deoxygenated blood into the pulmonary
circulation; the left side pumps oxygenated blood into the systemic circulation. ( 7 )
thepulmonary cycle.
The oxygenated blood is then pumped to the body through the systemic circulation before
returning again to the pulmonary circulation.
Systemic Circulation
Thesystemic circulationis the part of the cardiovascular system which carries oxygen-
rich blood away from the heart, to the body, and returns oxygen-poor blood back to the
heart. Oxygen-rich blood leaves the left ventricle through the aorta, from where it goes to
the body’s organs and tissues. The blood vessels that supply oxygen and nutrients to organs
and tissues are much smaller than the vessels that leave the heart. Recall that capillaries are
the smallest blood vessels. The tissues and organs absorb the oxygen, through the capillaries.
Oxygen-poor blood is collected from the tissues and organs by tiny veins, which then flow
into bigger veins. The inferior and superior venae cavae, are the large veins that return
oxygen-poor blood to the right side of the heart. This completes the systemic cycle. The
blood released carbon dioxide and gets more oxygen in the pulmonary circulation before
returning to the systemic circulation.