The heart is a muscular organ in human anatomy that pumps blood throughout the circulatory system. It's located in the middle of the chest, slightly to the left of the breastbone. The heart is about the size of your closed fist and weighs between 200 to 425 grams.
The heart has four chambers: two upper chambers called atria and two lower chambers called ventricles. The right atrium receives oxygen-depleted blood from the body through two large veins, the superior and inferior vena cava. It then pumps the blood to the right ventricle. The right ventricle pumps the blood to the lungs through the pulmonary artery for oxygenation. Oxygen-rich blood from the lungs returns to the left atrium through the pulmonary veins. The left atrium then pumps the blood to the left ventricle, the heart's strongest chamber. The left ventricle pumps the oxygen-rich blood throughout the body through the aorta, the largest artery in the human body.
The heart wall is made up of three layers:
- The epicardium, the outermost layer is a thin, transparent layer that protects the heart and secretes a lubricating fluid.
- The myocardium, the middle layer is the thickest layer and is composed of cardiac muscle tissue. This layer is responsible for pumping blood throughout the body.
- The endocardium, the innermost layer is a thin layer of endothelial cells that lines the inner chambers of the heart and valves.
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