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Other Terms: Cor, Corazon, Coeur, Herz, Cuore, Puso
The heart is a muscular organ of pyramidal shape. Its apex directs downward, anteriorly and to the left. It beats against the fifth intercostal space about two and a half centimeters to the medial side of the midclavicular line. It rests upon the central tendon and part of the left leaflet of the diaphragm and is posterior to the lower two-thirds of the sternum. It is suspended from the neck by the aorta, the three great branches of its transverse portion, and by the downward prolongation upon the aorta and pulmonary artery of the deep cervical fascia. This fascia blends with the pericardium. It is also supported from the roots of the lungs by the pulmonary arteries and veins. The direction of its base is the opposite of that of the apex. It directs upward, posterior, and to the right. The base occupies the same level as the middle four thoracic vertebrae, largely filling the space between them and the sternum. The front of the heart is composed mainly of the right ventricle below, and the right atrium above, only a narrow strip of the anterior edge of the left ventricle is visible on the left side. The right and lower portions are formed by the right ventricle. The heart has four chambers: two atriums and two ventricles. The upper, smaller, and weaker ones are the atriums. The lower and stronger one are called the ventricles. The atriums receive blood for transmission to the ventricles, which then force it onward. The right side of the heart forces the blood through the lungs for oxidation and the left side sends it through the body for nutrient purposes and oxygen distribution. The septa between these cavities are indicated by furrows. The right atrium and the right ventricle constitute the venous side. The left atrium and the left ventricle compose the arterial side of the heart. The furrows are called the interventricular and coronary sulcus. The interventricular sulcus is either anterior or posterior. The coronary sulcus is either right or left. They both lodge the coronary arteries. The size of the heart is about the size of the closed fist of the individual. In the adult it averages from twelve to fifteen centimeters in length; from nine to eleven centimeters in its greatest breadth, and from five to eight centimeters in thickness.