Title: Scheme of peripheral lung parenchym
Scheme peripheral lung, human.
(1) respiratory bronchiole.
(2) alveolar duct.
(3) alveolar sac is a virtual sac formed by several alveoli, but continuous with the alveolar duct.
(4) alveoli which end in small tips (↓) with elastin interwoven with collagen.
Title: Transition terminal bronchiole – respiratory bronchiole
Stain Azan, human. A longitudinal section shows the transition from the lumen of a terminal bronchiolus (1) into that of a respiratory bronchiolus (2). The epithelium of the terminal bronchiolus is regularly columnar and ciliated. The respiratory bronchiolus has an irregular lining and is covered by low columnar - cuboidal cells (↑); an alveolar pouch (3a) and few areas within the same lumen are lined by the common thin alveolar epithelium (small arrowheads) as found in the surrounding alveoli (3b). At (4) darker stained spots of irregular smooth muscle. (5) indicates a pulmonary artery and (*) smaller arterial branches. (6) showed carbon particles in macrophages.
Title: Respiratory bronchiole
Stain hematoxylin-eosin, mouse. The lumen (1) shows an irregular lining and is covered by low columnar - cuboidal cells (↓), locally disrupted by a few areas with thin alveolar epithelium as found in the surrounding alveoli (2). Thick arrows point to a row of light-stained Clara cells. At (*) discontinuous bundles of smooth muscle. (3) shows lymphocytic accumulation with macrophages that have phagocytized carbon particles.
Title: Alveolar duct in the lung
Stain PAS-hematoxylin, mouse. Part of an alveolar duct lumen (1) that shows bronchiolar characteristics such as cuboidal epithelium (2) covering a bundle of smooth muscle (3) and connective tissue containing macrophages (4) with black pigment deposits. Note PAS-positivity of these cuboidal cells (Clara cells) indicating the presence of glycogen. (5) alveoli with dilated capillaries (6) in its septa.
Keywords/Mesh: respiratory tract, lung, pulmonary artery, terminal bronchiole, respiratory bronchiole, alveolar duct, smooth muscle, atrium, columnar epithelium, cuboidal epithelium, Clara cell, alveolar epithelium, capillary, macrophage, phagocytosis, histology, POJA collection