TRANSMISSION ELECTRON-MICROSCOPY OF THE EPITHELIUM OF DISTAL AIRWAYS AND PULMONARY PARENCHYMA OF THE GOAT LUNG

Lungs from eight goats of mixed sexes and breeds (Cashmere, Nubian and Toggenburg) aged between 10 and 48 months were used in this study. Ti ssues from lung parenchyma were minced and routinely prepared for tran smission electron microscopy (TEM) after using different methods of fi xation. Thick sections were examined with a light microscope and sampl es, to include terminal bronchioles, respiratory bronchioles, alveolar ducts and alveolar membrane, were selected for ultrathin sectioning. Six cell types, ciliated, non-ciliated bronchiolar epithelial, mucus-p roducing, alveolar Type I, alveolar Type II and capillary endothelial cell were identified and characterised cytologically. II was establish ed that the cell population in the distal airways is similar to that o bserved in other domestic mammals. The mucus-producing cell, which app ears to be a common cell type in the distal airways of man and Rhesus monkey, was encountered particularly in adult goats in the present stu dy. This study has also established that the Clara cell of the goat sh ows some cytological differences from those of some other mammalian sp ecies by having a large amount of SER, particularly in the apical regi on. Lipid vacuoles were seen to be a feature of the alveolar Type II c ells; these do not appear to have been reported in other mammalian spe cies. The study has provided a basic understanding of the morphologica l features of the cell population of the epithelium lining the distal airways in the goat's respiratory tract. The difference in junctional complexes between the various alveolar epithelial cells perhaps signif y a different pattern of intercellular transport, thus influencing the pathogenesis and resolution of alveolar pulmonary edema.