FETAL LUNG, HISTOLOGY. FETAL LUNG, HISTOLOGY Histological section of a human fetal lung at the stage of 14 weeks of gestation. Staining with an anti CD81 antibody (member of the tetraspanin family), in brown, and with hematoxylin (for nuclear DNA), en blue. Magnification: 150x. At this stage the lung is immature and the future airways (e.g. bronchi) look like glands. The parenchyma and the forming cells (visualized by their nuclei in blue) are in monolayer, without differentiation The e