The Medial Wall of the Right Atrium

The correct orientation of the heart in situ has been stressed and the anatomic relationships of the medial wall of the right atrium have been described and illustrated.Each atrium lies behind and to the right of its corresponding ventricle and, as the plane of the septa is angled at approximately 45°to the median plane, the right atrium lies as much in front of the left atrium as alongside it.The area of overlap between the atria is small in both the anteroposterior and lateral views and the interatrial septum, which constitutes only the posterior half of the medial wall of the right atrium, is most accessible in the right anterior oblique projection.The anterior half of the medial wall of the right atrium is closely related from above downward to the first part of the aorta including the aortic valve, and to the left ventricular outflow tract through the membranous part of the interventricular septum. The right coronary artery and the right ventricular outflow tract are also important anterior relations.Transverse sections of the thorax in all age groups have shown that only one aortic valve cusp is truly anterior and it is suggested that the terms anterior, and right and left posterior should be used to designate the cusps and sinuses of the aortic valve.