tached. The appendix auricle is a small conical muscular pouch. It projects from the sinus forwards and to the left side, where it overlaps the root of the pulmonary artery.6 There are four main openings into the right atrium; the SVC, IVC, coronary sinus, and the atriculo-ventricular opening. The larger IVC returns blood from the lower half of the body and opens into the lowest part of the right atrium, near the septum. The smaller SVC returns blood from the upper half of the body and opens into the upper and front part of the right atrium. The coronary sinus opens into the right atrium between the IVC and auriculo-ventricular opening. It returns blood from the cardiac muscle of the heart and is protected by a semicircular fold of the lining membrane of the atrium, called the coronary valve. The auriculo-ventricular opening is the large oval aperture of communication between the right atrium and ventricle. There are two main valves located within the right atrium; the Eustachian valve and the coronary valve.3 The Eustachian valve is located between the anterior margin of the IVC and the auricule-ventricular orifice. It is semilunar in form. The coronary valve is a semicircular fold of the lining membrane of the right atrium, protecting the orifice of the coronary sinus. The right ventricle is triangular-shaped and extends from the right atrium to near the apex. Its anterior surface is rounded and convex and forms the larger part of the front of the heart. Its posterior surface is flattened, rests on the diaphragm muscle, and forms only a small part of this surface. Its inner wall is formed by the partition between the two ventricles, the septum, and bulges into the cavity of the right ventricle. Superiorly, the ventricle forms a conical structure called the infundibulum from which the pulmonary artery arises. The walls of the right ventricle are thinner than those of the left ventricle. The thickest par...
