Macrocirculatory

Macrocirculatory pathways refer to the part of the circulatory system formed by the large vessels that carry blood to and from the heart. These include the systemic circuit, via arteries and veins, and the pulmonary circuit, via the pulmonary arteries and veins. The macrocirculation contrasts with the microcirculation, which involves the capillaries where exchange with tissues occurs.

In the systemic circuit, the left ventricle pumps oxygenated blood into the aorta and its branches, distributing it to tissues through arteries and arterioles, then returning deoxygenated blood through venules and veins to the right atrium via the superior and inferior venae cavae. The pulmonary circuit moves blood to the lungs via the pulmonary arteries, where gas exchange occurs, and returns oxygenated blood to the left atrium via the pulmonary veins.

Key determinants of macrocirculation include cardiac output, systemic vascular resistance, arterial compliance, and mean arterial pressure. Blood flow is driven by pressure differences, and organ perfusion is influenced by both global controls—such as autonomic nervous system inputs and circulating hormones—and local factors that adjust vascular tone.

Clinical relevance: macrocirculatory diseases include hypertension, atherosclerosis, aneurysms, and occlusive disease of the peripheral arteries. Management focuses on reducing blood pressure, improving arterial health, and preventing cardiovascular events through lifestyle measures and pharmacotherapy, including antihypertensives, statins, and antiplatelet agents.

Relation to microcirculation: the macrocirculation provides bulk transport to the body's tissues, while the microcirculation handles exchange across capillary walls and the regulation of regional perfusion according to metabolic demand. The two domains interact; macrovascular dysfunction can impair microvascular flow and tissue perfusion, and microvascular pathology can influence systemic hemodynamics in certain conditions.