Topography Of The Lungs (Anterior View)
Because the apex of each lung reaches as far superiorly as the vertebral end of the ﬁrst rib, the lung usually extends about 1 inch above the medial third of the clavicle when viewed from the front. Thus, the lung projects into the base of the neck.
The anterior border of the right lung descends behind the sternoclavicular joint and almost reaches the midline at the level of the sternal angle. It continues inferiorly posterior to the sternum to the level of the sixth chondrosternal junction. There the inferior border curves laterally and slightly inferiorly, crossing the sixth rib in the midclavicular line and the eighth rib in the midaxillary line. It then runs posteriorly and medially at the level of the spinous process of the tenth thoracic vertebra. These levels are, of course, variable and apply to the lung in expiration. In inspiration, the levels for the inferior border are roughly two ribs lower. The anterior border of the left lung is similar in position to that of the right lung. However, at the level of the fourth costal cartilage, it deviates laterally because of the heart, causing a cardiac notch in this border of the lung. The inferior border of the left lung is similar in position to that of the right lung except that it extends farther inferiorly because the right lung is pushed up by the liver below the diaphragm on the right side.
The oblique ﬁssure of the right lung, separating the lower lobe from the upper and middle lobes, ends at the lower border of the lung near the midclavicular line. The horizontal ﬁssure separating the middle from the upper lobe begins at the oblique ﬁssure and runs horizontally forward to the lung’s anterior border, which it reaches at about the level of the fourth costal cartilage.
The oblique ﬁssure of the left lung is similar in its location to the corresponding ﬁssure of the right side. The left lung ordinarily has only two lobes, and there is usually no horizontal ﬁssure in this lung. Extra ﬁssures may occur in either lung, usually between bronchopulmonary segments and, in the left lung, between the superior and inferior divisions of the upper lobe, giving rise to a three-lobed left lung.
The lungs seldom extend as far inferiorly as the parietal pleura, so some of the diaphragmatic parietal pleura is usually in contact with costal parietal pleura. This
Area which, of course, varies in size with the phase of respiration is called the costodiaphragmatic recess of the pleura or the costophrenic sulcus. A similar but much less extensive area is present where the anterior border of the lung does not extend to its limits medially especially in expiration and the costal and mediastinal parietal pleurae are in contact. This area is called the costomediastinal recess.
The diaphragm separates the liver from the right lung and, depending on the size of the liver, from the left lung. The left lung is also separated by the diaphragm from the stomach and the spleen.
The nipple in males usually overlies the fourth intercostal space in approximately the midclavicular line. In females, its position varies, depending on the size and functional state of the breast.