Scanning Electron Microscopy of the Lower Respiratory Tract of the Adult Goat

Abstract

Surface characteristics of the lower respiratory tract of seventeen clinically normal, adult Cashmere goats of both sexes were studied with the scanning electron microscope (SEM). Samples were taken from cranial trachea, caudal trachea, extra pulmonary bronchus, caudal lobar bronchus, small bronchi, and lung parenchyma, the latter including bronchiole, terminal bronchiole, respiratory bronchioles, alveolar ducts and alveoli. The trachea and bronchi were characterized by a lining epithelium composed of ciliated, nonciliated microvillous and mucus-producing cells. The degree of ciliation was observed to decrease with decreasing airway diameter, whilst the number of nonciliated microvilli; were in the majority, with ciliated cells presenting poorly developed cilia.  Mucus-producing cells were not identified at this level with SEM. Respiratory bronchioles were seen to be present and well developed and their lining epithelium characterized by the presence of both Clara cell and ciliated cells. Alveoli were lined primarily by Type I pneumocytes amongst which occasional Type II pneumocytes were distributed Alveolar pores and alveolar macrophages were both rarely observed.