The human heart is a cone-shaped, four-chambered muscular pump located in the mediastinal cavity of the thorax between the lungs and beneath the sternum, designed to ensure the circulation through the tissues of the body.  

The cone-shaped heart lies on its side on the diaphragm, with its base (the widest part) upward and leaning toward the right shoulder, and its apex pointing down and to the left.

Structurally and functionally it consists of two halves-right and left. The right heart circulates blood only through the lungs for the purpose of pulmonary circulation. The left heart sends blood to tissues of entire body/systemic circulation.

The heart is contained in a sac called the pericardium. The four chambers are right and left atria and right and left ventricles. The heart lies obliquely across the thorax and the right side is turned to face the front. Viewed from the front, the sternocostal surface of the heart (Fig. 1.1)  mainly consists of the anterior walls of the right atrium, right ventricles and the left ventricle. A small part of the left atrium and left ventricle forms the left border and the apex is formed by the left ventricle. The right atrium and ventricle are separated by the anterior part of the atrioventricular groove, also called the coronary sulcus. The two ventricles are separated by the interventricular groove. The sharp inferior border separates the sternocostal surface from  the diaphragmatic surface. The inferior border meets the left border at the apex.