Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

The Science of Viscera (Splanchnology)
Respiratory System
Pleura

The pleura is a serous membrane that covers the Lungs on all sides, fusing firmly with the pulmonary parenchyma. The pleura covering the lungs (pulmonary or visceral pleura) extends from the lung ROOT onto the chest wall, forming a closed pleural sac (right and left) around each lung. The pleura lining the walls of the thoracic cavity is called the parietal pleura. The parietal pleura is subdivided into the costal pleura, adjacent to the Ribs, the diaphragmatic pleura, and the mediastinal pleura. Between the parietal and visceral pleura lies a narrow cleft, the pleural cavity, which contains a small amount of serous fluid. This fluid moistens the contacting surfaces of the visceral and parietal pleura, facilitating the smooth gliding of the lungs within the pleural cavities during Respiration.

At the junctions where one part of the parietal pleura transitions into another, there are formations known as pleural recesses, into which the inferior and anterior borders of the lungs extend only during a maximal inspiration. The deepest recess is the costo-diaphragmatic recess, formed at the transition of the anterior costal pleura into the diaphragmatic pleura.

Borders of the lungs and pleural cavities. In clinical practice, a precise knowledge of the BOUNDARIES OF THE lungs and pleural sacs is of great importance. This information becomes especially relevant in cases of Pneumonia, pleural diseases (Pleurisy), or the accumulation of significant amounts of fluid or Blood in the pleural sacs (due to Hemorrhage or trauma). Anteriorly, the apices of the lungs lie 3–4 cm above the first rib or 2 cm above the clavicle. The lower borders of the lungs and pleura are determined with reference to imaginary vertical lines projected along The Human Body. These include the parasternal line (running along the lateral margin of the Sternum), the midclavicular line (passing vertically through the midpoint of the clavicle), the anterior axillary line (running along the anterior axillary fold), the midaxillary line (extending downward from the deepest point of the armpit), the posterior axillary line (running along the posterior axillary fold), the scapular line (passing through the inferior angle of the scapula), and the paravertebral line (running alongside THE Vertebral Column through the costovertebral joints).

The anterior border of the lung extends from its apex through the sternoclavicular joint, and then through the midpoint of the junction between the manubrium and the body of the sternum. From there, the border courses downward to the Cartilage of the VI rib, where it continues into the inferior border. The inferior border of the lung runs almost horizontally: it crosses the VI rib along the midclavicular line, the VIII rib along the midaxillary line, the X rib along the scapular line, and the XII rib along the paravertebral line, where it transitions into the posterior border that ascends along the vertebral column. The inferior border of the left lung lies slightly lower than that of the right lung (by approximately one-half of a rib width).

The superior and anterior borders of the pleura coincide with those of the lung. The inferior border of the pleura is determined along the same anatomical lines as the lung, but situated one rib lower.