Pseudoglandular - canalicular period of developing lung (human, fetus)

Stain: Azan. Part of a bronchus (1) with young cartilage (2). The hyaline cartilage presents solitary chondrocytes embedded in the blue intercellular substance surrounded by a perichondrium (3). Note that the bronchus as well as the bronchial tubes (4) show an apical position of the epithelial nuclei and a light-stained basal part containing glycogen. The mesenchyme (5) condenses around the bronchial tubes and at (*) differentiates into smooth muscle cells. At the top left (6) the collageneous adventitia (blue) of an artery.