In life the separation between the parietal and visceral pleuras is only several micrometers.
Another distortion is the abnormally wide pleural space however, this fixation shrinkage artifact serves as a useful reminder that the lung is not normally attached to the chest wall. The diaphragm is quite elevated in Figure 1-2A, and is approximately 5 cm higher than its end-expiratory position in life. The vertical height of the lungs is only approximately 18 cm, which is well below that at FRC (see Fig. The main distortion is that the lungs are at low volume. 1-2A ) shows the gross anatomic arrangements and relationships. The two illustrations represent the extremes of the approaches to lung anatomy. Figure 1-2B shows a posterior-anterior chest radiograph of a normal human at functional residual capacity (FRC). Figure 1-2A shows a midfrontal section through the thorax of a frozen human cadaver. The position of the lungs in the chest and in relationship to the heart is shown in Fig. Videos 1-1 to 1-5 provide views of lung movements related to changes in tidal volume, airway pressures, and respiratory rate. The chapter finishes with comparison of the lung of mice and humans, an important subject given the widespread use of murine models in lung research. The diversity of secondary functions emphasizes the importance of the lung in homeostasis. Secondary functions of the lung also are important, such as surfactant synthesis, secretion, and recycling mucociliary clearance neuroendocrine signaling and synthesis and secretion of a myriad of molecules by its epithelial and endothelial cells. These essential functions are emphasized through the gross, subgross, histologic, and ultrastructural determinants of respiratory gas exchange in the normal human lung.
The second function is host defense against the onslaught of airborne pathogens, chemicals, and particulates. One function is ventilation-perfusion matching to deliver oxygen to the body and to remove carbon dioxide that is produced by the body ( Fig. The lung has two essential, interdependent functions.
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