circulatiecircuits

Circulatiecircuits, or circulatory circuits, are the networks of blood vessels that transport blood through an animal’s body. In humans and other vertebrates, the circulation comprises two primary loops: the pulmonary circuit and the systemic circuit. The heart functions as a central pump that drives blood into arteries, capillaries, and veins, maintaining a closed and continuous flow.

The pulmonary circuit moves blood between the heart and the lungs. The right ventricle ejects deoxygenated blood into the pulmonary artery, which branches to the lungs. After gas exchange, oxygenated blood returns to the left atrium via the pulmonary veins. The systemic circuit delivers oxygen and nutrients to body tissues; the left ventricle discharges blood into the aorta, which branches into arteries, capillaries, and veins that return deoxygenated blood to the right atrium.

Capillary networks are the sites of exchange, connecting arterioles and venules. The circuits are arranged in parallel, allowing collective regulation of blood flow and ensuring that changes in one organ have limited effects on others. Hemodynamics—driving pressure, flow, and resistance—are governed by heart rate and contractility, vessel diameter, blood viscosity, and neural and hormonal control.

Disorders affecting circulatiecircuits include hypertension, coronary or peripheral artery disease, heart failure, venous insufficiency, and portosystemic shunts. Diagnosis relies on imaging and functional testing such as Doppler flow studies, while treatment aims to optimize flow and reduce resistance through pharmacologic therapy, lifestyle changes, or surgical interventions.

See also: coronary circulation, cerebral circulation, hepatic portal system.