The Blood Circuits

Pulmonary circulation is the part of the cardiovascular system that carries deoxygenated blood away from the heart and to the lungs, returning oxygenated blood to the heart.

Systemic circulation is when the heart pumps oxygenated blood to the rest of the body, and to all your internal organs that need it. Deoxygenated blood is then returned back to the heart for it to be oxygenated again back at the lungs.