Deoxygenated blood (or venous blood) returns to the heart through the venous system of our circulation. The heart not only pumps blood under high pressure through the arteries in the body, but also sucks blood back from the body to the right atrium.
Venous blood is rich in carbon dioxide (CO₂) and poor in oxygen (O₂). It circulates through the pulmonary arterial tree and systemic veins. Deoxygenated blood receives oxygen as it passes through the lungs, becoming arterial (oxygenated) blood and returning to the natural cycle.
