Morphological characterization of the immune organs in ostrich chicks

Abstract

This study describes the anatomical, light microscopic, and ultrastructural characterization of the immune organs in ostrich chicks. In this study 6 healthy 8-week-old ostrich chicks were processed for light and transmission electron microscopy. Hematoxylin and eosin as well as improved Weigert staining were used for light microscopy. The small thymus, which clustered caudally along both sides of the neck, contained Hassall's corpuscles in the medulla. The cloacal bursa, which formed the hanging and lateral walls of the cloaca, enveloped the cloaca but did not form a truly independent bursa. Inside the bursa convex papillae were densely distributed on the surface of the folds, each with a single bursal nodule in the lamina propria. There were several round or elliptical structures, similar to ellipsoids, in the parenchyma of the spleen. Homogeneous acidophilic material was found to exist between the ellipsoid and the lymph tissue, and intermittent transverse striations were detected by transmission electron microscopy. These data indicate that the immune organs of ostrich chicks, especially the spleen and cloacal bursa, have numerous distinct, conformational, and structural features. The acidophilic material between the ellipsoid analog and circum-lymph tissue of the spleen, which was identified as collagen fiber, has not been reported in other animals.