Type I alveolar cell in the lung (human, adult)

Electron microscopy. At the top the alveolar space is lined by type I alveolar cell (1, pneumocyte I). The cytoplasm is well provided with organelles and few electron-dense lysosomes, and pinocytotic vesicles. These pneumocyte I cells cover the interalveolar septa that contain fibroblasts and bundles of thin collagen fibers (3) and darker-stained elastin fibers(4). At (2) the basal membranes of the alveolar epithelial cells