Fenestrae in the Alveolar Membrane of the Human Lung

For the study of alveolar membrane fenestrae in clinically normal lungs seven specimens from patients ranging in age from 5 to 66 years were fixed in distention with a formaldehyde-alcohol solution. Blocks of lung tissue were sectioned in 100 to 500 _µ thicknesses, then stained with French, Van Gieson's or silver nitrate stain. Some sections were stained with two, namely the French and Van Gieson's stains. After studying and describing the normal elastic fibrous architecture in the respiratory passages and alveoli of the acinus, the alveolar membranes were studied in detail. In each lung alveolar membrane fenestrae were found ranging in diameter from 20 to 100 _µ. In lungs in which the fenestrae were large they also appeared in greater numbers, frequently having more than one fenestra in an alveolar membrane. Invariably, degenerated elastic fibers, frequently raptured and recoiled, were found in the vicinity of a fenestra. Epithelial debris was seen within the fenestra in many instances, whereas macrophages loitered in their immediate environment. The theory that the formation of alveolar membrane fenestrae is due to a degenerative process synonymous with emphysema is discussed.