heart

The heart is a cone-shaped muscular ORGAN located in the thoracic cavity between the LUNGS, slightly toward the left side of the body. It functions as the central pump of the CIRCULATORY SYSTEM by continuously moving BLOOD through the body. The wall of the heart is mainly composed of CARDIAC MUSCLE called MYOCARDIUM. The inner surface is lined by the ENDOCARDIUM, while the outside is surrounded by a protective membrane called the PERICARDIUM. A muscular wall called the SEPTUM divides the heart into right and left sides. Each side contains two chambers: an upper ATRIUM that receives blood and a lower VENTRICLE that pumps blood out of the heart. The right side of the heart receives oxygen-poor blood from the body through the VENA CAVA and sends it through the PULMONARY ARTERY to the LUNGS for oxygenation. The left side receives oxygen-rich blood from the PULMONARY VEINS and pumps it through the AORTA to the rest of the body. Four HEART VALVES maintain one-way blood flow: the TRICUSPID VALVE, PULMONARY VALVE, MITRAL VALVE, and AORTIC VALVE. These valves open and close during each heartbeat to prevent backward movement of blood.

• Muscular organ that pumps blood throughout the body • Located between the lungs inside the chest • Divided into right and left sides by the septum • Contains four chambers: two atria and two ventricles • Heart valves maintain one-way blood flow • Right side pumps blood to the lungs • Left side pumps oxygen-rich blood to the body