8.4. Left Ventricle
This septum, which divides the right and left ventricles, has two parts: a membranous part (lies superiorly) and a muscular part (lies inferiorly), and these two parts are continuous with each other. The muscular component of the left ventricle is larger than that of the right ventricle. This is because the left ventricle needs to eject its blood at a higher pressure, as it will be travelling throughout the systemic circulation (i.e. the whole body). As such, the trabeculae carneae is well-developed in the left ventricle. The right ventricle is only pushing blood to the lungs and its muscular wall is not just as well developed.
Note the presence of the bicuspid valve (also called the left atrioventricular valve). It has two cusps (one anterior and one posterior) that are associated with chordae tendineae and their respective anterior and posterior papillary muscles.
The aortic vestibule
This is a fibrous area just below the aortic orifice/opening. Its smooth surface is a key part of smooth blood flow out of the ventricle. The same area in the right ventricle would be the infundibulum.