Q. Describe the pulmonary artery?

The main pulmonary artery is seen on the PA view, as its left border forms the pulmonary bay. The right pulmonary artery runs horizontally to the right within the mediastinum and is not seen on the frontal view. Its upper lobe branch is given off in the mediastinum. Thus, the descending branch of the right pulmonary artery is the vessel first identified, as it forms the lower part of the right hilum. On the lateral view, it is seen as a rounded density just anterior to the carina. The left pulmonary artery, along with its descending branch are identified on the plain film as it forms part of the left hilum and continues into the lower lobe. On the lateral view, it is seen over the left main bronchus, superior and posterior to the right pulmonary artery. The pulmonary arteries within the lung parenchyma, are closely related to the bronchi and taper gradually, as they branch.