Anatomic Changes in Lung Parenchyma Due to Aging Process

¹ First Department of Internal Medicine, School of Medicine, Tohoku University

We studied the volumetric fraction of the respiratory portion (respiratory bronchioli, alveolar ducts, alveolar sacs and alveoli) for nine autopsied lungs aging from the fourth day after birth to 68 years old, by means of gravimetric method, using the macrosection specimen. All lungs did not show any pathologic changes. Furthermore, in order to analyze the distribution of the volumetric fraction, the histometric method for the same lung was used.

We found that the alveoli developed rapidly in the infant and child lungs and the development of the respiratory portion continued until about 20 years of age. In the range of 20-40 years of age, the volumetric fractions were maintained almost constant, i.e., about 60 per cent for the alveoli and 40 per cent for the central ducts. On the other hand, in the senile lungs, the volumetric fraction of the central ducts was relatively higher than that in the young adults. The important feature for the senile lungs is the relative higher volumetric fraction of the central ducts, compared to that of the alveoli. This would be due to the dilatation of the central ducts.