Slide A
This low power view shows well-inflated lung parenchyma. Note the alveoli, alveolar ducts, and bronchovascular bundles. The alveolar septa are thin and delicate, and only rare cells (alveolar macrophages) are found in the airspaces.

Slide B
The terminal bronchioles, the last branches of the bronchial tree completely lined by bronchial epithelium, are distinctive in their histologic appearance. The bronchiolar mucosa has a scalloped or pleated contour, and there is no cartilage in the wall. The diameter of the accompanying muscular pulmonary artery is of roughly equal caliber to that of the bronchiole.