The systematic venous return to the heart is via the superior and inferior vena cava, which connect to the superior and inferior portions of the right atrium. The right atrium also receives flow of desaturated blood from the coronary sinus. Within the body of the right atrium is the Eustachian valve, which directs flow from the inferior vena cava. The right atrium connects to the right ventricle via the trileaflet tricuspidvalve. The tricuspid valve has attachments to the right ventricular septum as well as free wall.
The right ventricle is a coarsely trabeculated pumping chamber, which becomes more smooth-walled as it transitions to the pulmonary outflow/subpulmonary valve area. The pulmonary valve is a trileaflet semilunar valve that sits to the left and anterior af the aortic valve. The main pulmonary artery branches into right and left pulmonary arteries, which conneet to respective lung hila. Four pulmonary veins return oxygenated blood from the lung hila to the posterior right and left portions of the left atrium. The left atrium also contains a finger-like left atrial appendage. The two atria are separated by the atrial septum, which consists of a thicker septum secundum and thinner septum primum.
