The Heart

The circulatory system consists of two circuits, the pulmonary circuit that circulates blood to and from the lungs, and the systemic circuit that circulates blood through the body.

Circulatory System Video

The heart is surrounded by a fluid-filled membrane called the pericardium. The pericardial fluid bathes the heart, preventing friction between its outer wall and the membrane.

The heart is composed of cardiac muscle called the myocardium

Heart Parts Superior Vena Cava Inferior Vena Cava Pulmonary Veins Pulmonary Arteries Aorta Right Atrium Right Ventricle Left Atrium Left Ventricle Tricuspid Valve Mitral Valve Aortic Valve Pulmonary Valve

The heart is supplied by its own set of blood vessels The heart is supplied by its own set of blood vessels. These are the coronary arteries. There are two main coronary arteries, the right and left coronary arteries

Control of the Heart Beat Sinoatrial node (SA node) produces the impulse that starts each heartbeat. The electric impulse spreads quickly over both atria causing them to contract. The impulse then reaches the atrioventricular node (AV node), causes nerve impulses to be sent down the bundle of nerve fibers, known as the Bundle of His. The impulse reaches the muscles of the ventricles and causes them to contract. The heart has special muscle fibers called Purkinje fibers

Video (circulatory system 1)