Title: Lung alveoli
Stain Azan, human. Alveoli (diameter about 200 µm) are formed by thin walls of epithelial cells (1) such as type I alveolar cells and (blue stained) fine collagen (3) and elastin intermingled with dilated capillaries (2).
Keywords/Mesh: respiratory tract, lung, alveolus, alveolar cell, cytokeratin 7, type I pneumocyte, type II pneumocyte, alveolar macrophage, Air-Blood barrier, capillary, histology, electron microscopy, POJA collection
Background of cytokeratin 7:
This antibody can be used in the study of alveolar developmental processes in the lung, or of various types of bronchial carcinoma as well in the differential diagnosis between various types of carcinoma in the lungs.
Title: Keratin 7 in the lining alveolar epithelium of the lung
Anti-keratin 7 antibody (Pan-Ck 7) immunoperoxidase staining (with aminoethylcarbazole (AEC) substrate), human. Both alveolar epithelial cell types I (1) and II (2) stain dark brown-red after the reaction with AEC indicating a positive reaction for cytokeratin 7.
Note the white (non-stained) capillaries (↓) sandwiched between the red-brown reacting alveolar epithelial cells (air-blood exchange). Within the alveolar lumen alveolar macrophages (M) appear negative for keratin 7.
Title: Air-Blood barrier in the lung
Scheme electron microscopy, human.
(1, ↓): Represents type I pneumocytes lining alveolar spaces (A).
(2): Cell (2) represents a free alveolar macrophage.
(3): The type II pneumocyte (3) is adherent to type I pneumocyte extensions (note junctional connection), and contains multilamellar bodies (surfactant).
(4): A myofibroblast (4) is located in the interstitium (note surrounding cross-sectioned collagen fiber dots), and (*) indicate elastin.
(5, ↓): Indicate endothelial cells within the capillaries.
(6↔): Indicates the thin-walled area of the air-blood barrier.
Title: Alveolus in lung
Electron microscopy, dog.
(A): Indicate alveolar space;
(C): Indicate capillary with erythrocyte. Drawing-pin represents endothelium.
(1): Type I alveolar cell; (↓) indicate thin cytoplasm of pneumocyte I. (2): Type II alveolar cell.
(3): Alveolar macrophage. (*) are spots of elastin, intermingled with collagen.
(4): Interstitial myofibroblast. (↔) thin-walled area of the air-blood barrier.
Thin-walled areas are most favourable to gas exchange and alternate with thick-walled areas (thick arrow, ◄▬►) consisting of supporting fibers, extracellular matrix and cells of the alveolar framework that separate the alveolar epithelium from the capillaries.