The heart has two ventricles, which includes a right and a left one.

The right ventricle receives blood from the right atrium during ventricular diastole and propels blood into the pulmonary circulation during ventricular systole (figures 104a, 105a, 105b). The right ventricle is normally the most anterior cardiac chamber, lying directly beneath the sternum. The right ventricle is partially below, in front of, and medial to the right atrium but anterior and to the right of the left ventricle. The striking difference in configuration between the two ventricles illustrated by a transverse section (figures 104a, 105a).

The left ventricular chamber is an ellipsoidal sphere surrounded by thick musculature, well suited to ejecting blood against the high resistance of systemic vessels.

The right ventricle (RV), which normally contracts against very low resistance, has a crescent- shaped chamber and a thin outer wall. The anterior and inferior walls of RV cavity are lined by muscle bundles (trabeculae carneae). There is also a rather constant muscle, the moderator band, which crosses from the lower ventricular septum to the anterior wall, joining the anterior papillary muscle. The right bundle courses through the moderater band to reach the endocardium.

The left ventricle (LV) (figures 104b, 105a, 105b) receives blood from the left atrium during ventricular diastole and ejects blood into the systemic circulation during ventricular systole. The LV is bullet shaped with a blunt tip directed anteriorly, inferiorly, and to the left, where it contributes to,with the lower ventricular septum,to the apex of the heart. The major portion of its external surface is posteriolateral.The LV is posterior and to the left of the RV and inferior, anterior, and to the left of the left atrium. The LV chamber is an ellipsoidal sphere,surrounded by thick muscular walls,about three times the thickness of the RV wall. The ventricular septum is the medial wall of the LV. The lower 2/3 of the LV is ridged with by interlacing muscles, the trabeculae carneae.