A mouse lung obtained at postnatal day 4 represents the endpoint of branching morphogenesis just before alveolarization starts. The video starts with a view of the turning block. Flying half way through a conducting airway the viewer turns left and enters the gas-exchange area. The path ends in a saccule. Inside the saccule a small rising up of the wall is visible. It represents the first sign of alveolarization.
At day 36 the rat lung represent the young adult stage, however alveolarization is still ongoing. The video starts with a view onto the block. The viewer enters a terminal bronchiole, turns right through a very short respiratory bronchiole into an alveolar duct and flies it down until one of its ends in front of two alveoli. Two remarkable features are seen in the videos. First, the cobblestone like inner surface of the terminal bronchioli which represent cells of Clara. Second, the sponge like appearance of the gas-exchange area. However, it should be remembered that an acinus is not built like a sponge. The acinar airways resemble a small tree of branched tubes where the walls are constantly interrupted by the entrance rings of alveoli.
Wide Field Scan
Rotating Sample stitched from 5 overlapping Projections