The heart is inside the chest cavity and does not change with changes in postural position; therefore, the heart remains inside the chest cavity when the body is flexed. The heart is located in the thoracic cavity, specifically above the diaphragm and between the two lungs, about two-thirds of the way to the left of the midline. The heart is shaped like an inverted, slightly flattened cone in front and back, more like a peach. The apex of the heart is bluntly rounded, facing left anteriorly and inferiorly, and is adjacent to the anterior chest wall. The surface projection of the interstitium of the heart is about 0.5-1.0 cm medial to the midclavicular line at the fifth intercostal space on the left anterior chest wall, and the apical pulsation can therefore be seen or palpated here. The base of the heart is wider, with large blood vessels entering and exiting here, toward the right posterior-superior aspect of the heart, and adjacent to the esophagus and other organs of the posterior mediastinum.