The general shape and orientation of the heart are that of a pyramid that has fallen over and is resting on one of its sides. Placed in the thoracic cavity, the apex of this pyramid projects forward, downward, and to the left, whereas the base is opposite the apex and faces in a posterior direction (Fig. 3.63). The sides of the pyramid consist of: a diaphragmatic (inferior) surface on which the pyramid rests, an anterior (sternocostal) surface oriented anteriorly, a right pulmonary surface, and a left pulmonary surface.