CELL NUMBER AND CELL CHARACTERISTICS OF THE NORMAL HUMAN-LUNG

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Abstract
Eight normal human lungs obtained from patients dying from causes not related to the lung were subjected to morphometric analysis to determine the number of cells in the alveolar region and their mean volume and surface characteristics. The age range was 19-40 yr, average body weight was 74 kg, and the average fixed lung volume was 4300 ml. The overall mean nuclear diameters of the nuclei of 5 major cell types in the lung parenchyma had little variation, with means ranging from 7.54 to 8.77 .mu.m. Alveolar type I epithelial cells comprised 8% of the cells and were one of the largest cells, having a mean volume of 1764 .mu.m3 and covering an average of 5098 .mu.m2 of alveolar surface. Of the alveolar surface, 7% was covered by alveolar type II cells, which make up 16% of the total alveolar cells and have a mean volume that is half that of the type I pneumocyte. Capillary endothelial cells make up 30% of the lung cells and were significantly smaller in size and average surface area than the alveolar type I cells. Cells in the interstitial space comprised 37% of the total cells. Number of alveolar macrophages showed great variability, ranging from 19% of alveolar cells in 1 person to 3-5% in the nonsmoking females. Alveolar cell population characteristics in resected lobes from 2 nonsmoking females were similar to 2 nonsmoking females studied after autopsy. An interspecies comparison of characteristics of cells from the alveolar regions of normal lungs from humans, baboons and rats showed that proportions of cells in the alveolar region and their average thickness, size and surface areas were relatively constant.