ABSTRACT
The lungs are ingeniously constructed to carry out their cardinal function-the exchange of gases between inspired air and the blood. The gas exchange region of the lung is composed of respiratory bronchioles, the alveolar ducts, the alveolar air space, and the alveolar walls. The alveolar walls are composed of the capillary endothelium, the alveolar epithelium, and the intervening extracellular matrix (ECM) organized into the basement membranes of the two cell layers and the interstitial tissue. The lung ECM components include collagens, elastins, proteoglycans, and noncollagenous glycoproteins, such as laminin and fibronectin. Collagens and elastins together constitute over 60% of the dry weight of the lung.
