The left ventricle is longer and more conical shaped than the right ventricle. It forms a small part of the left side of the anterior surface of the heart and a large portion of the posterior surface. It also forms the apex of the heart because it extends beyond the right ventricle. Its walls are nearly twice as thick as those of the right ventricle. They are thickest in the broadest part of the ventricle, becoming gradually thinner towards the base and also towards the apex, which is the thinnest part of the left ventricle. There are two main openings in the left ventricle; the atrial-ventricular opening and the aortic opening. The atrial-ventricular opening is located behind and to the left side of the aortic opening. The opening is a little smaller than the same opening between the right atrium and ventricle. Its position corresponds to the center of the sternum. It is surrounded by a dense fibrous ring and is covered by the lining membrane of the heart and is protected by the mitral valve. The circular aortic opening is located in front of and to the right side of the atrial-ventricular opening from which it is separated by one of the segments of the mitral valve. The opening is protected by the semilunar valves. There are two valves located within the left ventricle; the mitral valve and the semilunar valve. The mitral valve is attached to the circumference of the atrial-ventricular opening in the same way that the tricuspid valve is attached on the opposite side of the heart. The valve contains a few muscular fibers, is strengthened by fibrous tissue, and is formed by the lining of the heart (endocardium). It is larger, thicker, and stronger than the tricuspid, and consists of two segments of unequal size. The mitral valves are connected to many chordae tendonae. Their attachment is the same as on the right side except they are thicker, stronger, and less numerous. The semilunar valves surroun...
