The heart has four blood collecting chambers, two atria and two ventricles. On the left side of the heart are the left atrium and the left ventricle. On the right side of the heart are the right atrium and the right ventricle.
The superior vena cava, the inferior vena cava, the coronary sinus and the anterior and small cardiac veins open into the right atrium. This means that the right atrium receives deoxygenated blood. On the posterior surface of the right atrium contains a smooth walled area known as the sinus venarum. This segment of the right atrium contains the openings of the inferior and superior vena cava, and the coronary sinus as well as the valve of the inferior vena cava and the valve of the coronary sinus.
In contrast to the posterior segment, the anterior segment of the right atrium is not smooth. It contains the right auricle and crista terminalis from which the pectinate muscles arise. At the level of the interatrial septum, which separates the left and right atria, is the fossa ovalis, a remnant of the fetal foramen ovale and it is has an oval margin known as the limbus of fossa ovale.
The atrioventricular orifice is the opening between the right atrium and the right ventricle that is guarded by the right atrioventricular valve. The right ventricle receives doexygenated blood from the right atrium, which is then pumped through the valve of the pulmonary trunk and into the pulmonary trunk via rhythmic contraction.
The supraventricular crest and the septomarginal trabecula divide the right ventricle into two segments; an inflow segment that contains chorda tendinae, papillary muscles and trabeculae carnae, and an outflow segment which consists of the cornus arteriosus.
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