Anatomic changes in lung parenchyma due to aging process.

of the lungs, including alveoli, is usually divided into two portions, i.e., the airway and the respiratory portion. Although the latter is morphologically subdivided into the respiratory bronchioli, alveolar ducts, alveolar sacs and alveoli, it will be much more useful to divide the respiratory portion into two parts, i.e., the central ducts succeeding the airway and alveoli surrounding the central ducts. In 1961’ we found morphologically the dilatation of the central ducts in the senile lungs. Recently, Weibel’ investigated the volume contribution of the central ducts and alveoli for five excised lungs from patients from 8 to 74 years old. He found that the volume contribution of the alveoli, corresponding to the alveolar air, was higher (62 per cent) than that of the central ducts in three younger individuals. On the contrary in two older individuals this value decreased by 56 per cent. In his paper he stated, “The small number of cases obviously does not justify conclusive statement with respect to changes of volume proportion of the lung generally attributable to age.” At this point, it is necessary to notice that in his estimation of volume contribution, the volume fraction of the respiratory bronchioli was not included. It would be due to the difficulty to estimate the volumetric fraction of this part by means of his modified method, applying Delesse and Rosiwal’s principles. The purpose of this paper is to estimate the variation of the volume contribution between the alveoli and central ducts including respiratory bronchioli by means of our new method with respect to the aging process. METHOD