<unk>  is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. The term is contrasted with systemic<unk> .
Pulmonary circulation
Systemic circulation
Coronary circulation
Arteries of the head and neck
Arterial tree
Hepatic circulation
Coronary arteries
Cardiac veins