This illustration demonstrates a posterior view of the thoracic cavity, highlighting the position of the heart in relationship to the ribs and diaphragm. The left atrium, left ventricle, and coronary sinus in the coronary sulcus between these chambers can be easily seen from the posterior aspect. Note that in most cases, 2/3 of the heart is positioned to the left of midline and the inferior aspect is resting on the diaphragm, with the other 1/3 positioned to the right. The apex of the heart is pointing inferiorly and to the left, causing the long axis of the heart to be at an acute angle to the long axis of the body.