Ultrastructure of the camel's pulmonary alveoli with special reference to the air-blood barrier [with 7 figures]

ABSTRACT

The present study was conducted to characterize the cellular population lining the alveoli of the camel's lung. It focused on the ultrastructural findings and their reflection on the physiological role in gas exchange and transcytosis through the air-blood barrier [ABB]. It was carried on adult camel using electron microscope. Ultrastructural examination revealed that the pulmonary alveoli were lined with a continuous epithelium comprising two major cell types; the predominant, attenuated pneumocyte type I and the less popular, irregularly cuboidal pneumocyte type II. Two 'forms of fibroblasts were distinguished; the most remarkable feature of the first form was its well-developed and abundant rough endoplasmic reticulum. The second form was characterized by large, irregular, dark stained nucleus and little amount of cytoplasm. The most obvious feature of endothelial cells was the concentration of small vesicles [pinocytotic vesicles] adjacent to the endothelial cell membranes. They were circumscribed by a continuous basal lamina. Along the same endothelial cell, two cytoplasmic zones were existing; a thin cytoplasmic area containing few or no plasmalemmal vesicles [avesicular area] and another thicker cytoplasmic area with numerous plasmalemmal vesicles and endocytotic pits [vesicular area]