Interacinar pathways in the human lung

Normal lung specimens from patients 18 to 86 years of age were inflated, fixed, and cleared. After micropuncture of the distal airspaces and injection of silicone rubber, the dissemination pattern was studied by cinematography. Free interacinar flow was commonly observed. The major pathways of spread among adjacent acini were the interacinar ducts. These were short, tubular structures 200 mum in diameter that were continuous with respiratory bronchioles and alveolar ducts. The flow of silicone rubber was impeded only by the septa of the secondary lobule of Miller. Our finding support the view that the smallest morphologic unit of airspace disease is more likely to be the secondary lobule than the acinus.