Morphology of the Acinus of the Human Lung

¹ Clinical Instructor of Medicine, University of British Columbia, Vancouver

Further morphologic studies of the human lung acinus were undertaken by means of microdissection of latex corrosion models. Two human lungs, one from an elderly man and another from a 26-year-old woman were used for the preparations. Four acini, two from each lung, were dissected in detail. A distinct difference was noted between the acini from the elderly man and those from the 26-year-old woman's lung. The terminal bronchiole always divides dichotomously, whereas the respiratory bronchioles divide by dichotomous, trichotomous and even quadrivial division. Unusual types of branchings are described. Approximately 40 percent of the alveoli of the acinus are located on respiratory bronchioles, including alveolar ducts, whereas 60 percent are on the alveolar sacs. A similar ratio exists between the volumes of the respiratory branches and the alveolar sacs. From the data obtained the acinar volumes, alveolar surface area and number of alveoli present in the lung were calculated.