There is an oval depression in the center of the medial side of the lung called the pulmonary hilum. It corresponds to the area between the 2nd and 4th anterior ribs and is the entrance and exit point for the bronchi, blood vessels, nerves and lymph. The right pulmonary hilum is close to the sternum, while the left pulmonary hilum is influenced by the heart slightly away from the sternum. At the pulmonary hilum, the pulmonary veins are positioned anteriorly, the bronchi are posterior, the pulmonary arteries are in the middle, and there are several lymph nodes in the pulmonary hilum. The aortic arch and thoracic aortic indentation are located above and posterior to the left pulmonary hilar, and the right pulmonary hilar has an esophageal indentation posteriorly and an odd vein groove above.