Morphology of the esophageal mucosa in long-eared owl and eurasian jay

Abstract

The morphology of the esophageal mucosa in long-eared owl (Asio otus) and Eurasian jay (Garrulus glandarius) has been studied. Samples with exception of the region of the esophageal tonsil were obtained from 3 adult birds of each species. They were studied by light microscopy using classical methods of morphological research. The tissue samples were fixed in 10% neutral buffered formalin and embedded in paraffin block and finally the section were cut at 5–10 µm thickness using sliding microtome and stained with hematoxylin and eosin, according to Van Gizon and Weigert and impregnated with silver nitrate according to Kelemen. The esophageal mucosa consisted of four layers: epithelium, lamina propria, muscularis mucosae, and submucosa. The epithelium was stratified squamous and better developed in the cranial part of the esophagus. The lamina propria was represented by a loose connective tissue with small amount of elastic fibers. In the long-eared owl tightly located numerous small secretory sections of the esophagus glands organised in 1–3, and in branches of large folds up to 6 layers, were found. Their short excretory ducts opened to the surface of the mucosa. The muscularis mucosae was represented by a smooth muscle tissue with bundles of cells directed longitudinally and in some areas appeared to be absent. The submucosa was well developed, and as well as lamina propria was formed by a loose connective tissue with a large number of elastic fibers. In the submucosa of the Eurasian jay secretory departments of large, not tightly located, esophageal mucous glands were found. The esophageal mucosa of this birds formed well-developed folds, which were composed of all its layers. Their number in the long-eared owl was 20–25 and in the Eurasian jay – 5–9. The shape of folds on the transverse section is not the same: in the long-eared owl it was finger-shaped and leaf-shaped, but in the Eurasian jay it was wedge-shaped. Some large folds in the long-eared owl branched into the secondary mucosal folds. The height of folds in cranial part of the esophagus was larger than in caudal part. In both parts of the esophagus of long-eared owl the height of the large and middle folds was larger than that in the Eurasian jay. The height of small folds in the Eurasian jay was greater than that in the long-eared owl. In both parts of the esophagus of this birds, the fold’s width at the base exceeded its width at the top. In the Eurasian jay the width of base and top of large, medium and small folds was larger than that in the long-eared owl. The esophageal mucosa was poor on immune formations. They were represented by single accumulations of diffuse lymphoid tissue, and in the Eurasian jay – even by secondary lymphoid nodules.