The influence of inflation levels of the lung on the morphology of the visceral pleura.

The visceral pleura was shown ultrastructurally to be a tightly adhering covering which follows closely the contour of the underlying lung parenchyma. The outer mesothelial layer was comprised of flattened cells when the lung was inflated and transformed into regions of more cuboidal cells after lung collapse. The only distinguishing factors between the visceral pleura of the younger and older animals were the increased connective tissue in the submesothelial areas of the latter and the increased numbers of vesicles found in their basal lamina. The varying degrees of lung inflation can result in marked alterations in the characteristics of the mesothelial layer of the visceral pleura.