The posterior border is smooth and rounded (in contrast to the anterior and inferior borders, which are sharp). The inferior border separates the base of the lung from the costal and mediastinal surfaces. On the left lung, the anterior border is marked by a deep notch, created by the apex of the heart. The anterior border of the lung is formed by the convergence of the mediastinal and costal surfaces. It is related to the costal pleura, which separates it from the ribs and innermost intercostal muscles. It faces the internal surface of the chest wall. This concavity is deeper in the right lung, due to the higher position of the right dome overlying the liver. It rests on the dome of the diaphragm, and has a concave shape. The base of the lung is formed by the diaphragmatic surface. The lung hilum (where structures enter and leave the lung) is located on this surface. The mediastinal surface of the lung faces the lateral aspect of the middle mediastinum. There are three lung surfaces, each corresponding to an area of the thorax. The oblique fissures are similar in both lungs Surfaces The left lung contains superior and inferior lobes, which are separated by a similar oblique fissure.įig 2 – The lobes and fissures of the lungs. Horizontal fissure– Runs horizontally from the sternum, at the level of the 4th rib, to meet the oblique fissure.Oblique fissure – Runs from the inferior border of the lung in a superoposterior direction, until it meets the posterior lung border.The lobes are divided from each other by two fissures: The right lung has three lobes superior, middle and inferior. The right and left lungs do not have an identical lobular structure. Borders (three) – The edges of the lungs, named the anterior, inferior and posterior borders.They are named costal, mediastinal and diaphragmatic. Surfaces (three) – These correspond to the area of the thorax that they face.Lobes (two or three) – These are separated by fissures within the lung.Base – The inferior surface of the lung, which sits on the diaphragm.It projects upwards, above the level of the 1st rib and into the floor of the neck. Apex – The blunt superior end of the lung.The left lung is slightly smaller than the right – this is due to the presence of the heart.

The lungs are roughly cone shaped, with an apex, base, three surfaces and three borders.

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