生理学的に見た肺の構造

The Structure of Lung from the Phyisiological Point of View.

はじめに

　近時，肺生理学の研究が活発となるにともない，肺構造の研究も従来の主観的観察から逸脱し肺生理学との関連性を考慮に入れて，定量的な取り扱いをすることが望まれるようになった。本邦においても既に先年来，諏訪一門によってこの分野への開拓が着々と進められているが，ここでは私どもの経験などをも含めてかかる研究動向の二，三を紹介したいと思う。

Lung parenchyma (respiratory bronchiole, alveolar duct, alveolar sac) consists of the canal system (central ductal space) and the alveoli attaching to it. This lecture is the study of the morphometry of the human lung parenchyma.

1) According to Weibel, the number of alveoli could be estimated by the following three different methods. a) Direct counting method, b) Linear integration method, c) Cal-culation of the diameter of the alveolus by determining the alveolar surface area. These procedures were described.

2) The volume of the canal system and the alveoli was quantitated by the gravimetrical technique of macrosection specimen, in which the specimen was projected on a photographic paper and the paper was cut off along the margin of the canal system and the alveolus. In four adult subjects aged from 20 to 40 years old, the volumetric fraction of the alveoli, by this method, comprised the av-erage 60% of the lung parenchyma. Relative decrease of the alveolar fraction and increase of the volumetric fraction of the canal system were shown in older persons.

3) The structural particularity of the re-spiratory bronchioles of the first order, contributable to a causing mechanism of the acinal involvement, was studied with in-troduction of hydrodynamics.

4) Weibel, Hennig and Suwa have already reported the methods of estimating total alveolar surface area. In our results, the value of total alveolar surface area using lungs of 3 female adults was approximately 40~60m².

5) Using the methods of Weibel and Suwa, the dichotomy model of airway in the lungs was studied to make a calculation of airway resistance and its localization. The results showed the unexpected increase of airway resistance in the portion between the seg-mental bronchi and the small bronchi proxi-mate to the bronchiole.

6) Suwa's histometrical method of the distribution of the peripheral airway was introduced.

7) The total capillary surface area and total capillary volume were calculated by Weibel's method, in which Indian ink was injected into the pulmonary artery of autopsied human lung and dimensions of alveolar capillaries were mathematically treated. In three female subjects, the total capillary surface area and volume were estimated at about 40m² and 80 cm³ respectively. These values showed a tendency to decrease in older persons.