heart and blood vessel disorders
Biology of the Heart
Introduction
The heart and Biology of the Blood Vessels constitute the cardiovascular (circulatory) system. The heart pumps the The heart, a hollow muscular organ, is located in the center of the chest. The heart has two sides, right and left. The right and left sides of the heart each have an Atrium:Upper chamber that collects blood and pumps it to the lower chamber Ventricle:Lower chamber, which pumps blood out of the heart To ensure that blood flows in only one direction, each ventricle has an "in" (inlet) valve and an "out" (outlet) valve. In the left ventricle, the inlet valve is the mitral valve, and the outlet valve is the aortic valve. In the right ventricle, the inlet valve is the tricuspid valve, and the outlet valve is the pulmonic (pulmonary) valve. Each valve consists of flaps (cusps or leaflets), which open and close like one-way swinging doors. The mitral valve has two cusps. The other valves (tricuspid, aortic, and pulmonic) have three. The large inlet valves (mitral and tricuspid) have tethers—consisting of the papillary muscles and cords of tissue—which prevent the valves from swinging backward into the atria. If a papillary muscle is damaged (for example, by a Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) ), the valve may then swing backward and start The heartbeats are evidence that the heart is pumping. Doctors often describe the sound of the heartbeat as lub-dub. When doctors listen to the heartbeat with a stethoscope, the first sound they hear (the lub of lub-dub) is the sound of the mitral and tricuspid valves closing. The second sound (the dub) is the sound of the aortic and pulmonic valves closing. Each heartbeat has two parts: Systole:During systole, the ventricles contract and pump blood out of the heart, and the atria relax and begin filling with blood again. Diastole:During diastole, the ventricles relax and fill with blood. Then the atria contract, forcing more blood into the ventricles. 