The Cardiovascular System: Heart and Circulation

The cardiovascular system consists of the heart and blood vessels that circulate blood throughout the body. The heart is a four-chambered pump with two atria (receiving chambers) and two ventricles (pumping chambers).

The pulmonary circuit carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium. The systemic circuit carries oxygenated blood from the left ventricle to the body and returns deoxygenated blood to the right atrium.

The cardiac conduction system (SA node, AV node, bundle of His, Purkinje fibers) generates and coordinates heartbeats. The heart beats approximately 100,000 times per day.

Blood vessels include arteries (carrying blood away from the heart), veins (returning blood to the heart), and capillaries (sites of gas and nutrient exchange). The arterial system branches progressively from the aorta to arterioles to capillary beds.