Normal chest X-ray, PA view demonstrating cardiovascular structures. RPA: right pulmonary artery; LPA: left pulmonary artery; MPA: main pulmonary artery. Right heart border is formed by the right atrium. Linear shadow above the right atrial contour is the superior vena cava along the right para spinal region. Left heart border is formed by the main pulmonary artery segment above and the left ventricle below. The mild depression in between is the region of the left atrial appendage. Apex is formed by the left ventricle in the normal chest X-ray. The left heart border is seen extending below diaphragm and is seen through the fundal gas bubble. Right ventricle is not a border forming structure in PA view.