Histomorphological study of the lymphoid tissues of broiler chickens

Abstract

Topology and histology were performed in the lymphoid tissues (thymus, bursa of Fabricius, spleen and cecal tonsils) of the fifteen 28-days-old "Kasilla" broilers by observation of H & E stained sections in the Department of Anatomy and Histology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh during the period from October to December 2005. In the present study, it was observed that the thymus was enclosed by a thin connective tissue capsule. Numerous fine septa of connective tissue originated from the capsule and divide the organ into incompletely separated lobules. Each lobule organized into a peripheral cortex and a central medulla. The population of the immunocompetent cells (lymphocytes and immunoglobulin containing plasma cells) in the cortex were denser rather than that of medulla of the thymic lobule. The bursa of Fabricius was consisting of long thick mucosal folds (plicae). Numerous follicles filled the lamina propria of each fold and each bursal follicle was composed a peripheral cortex and a central medulla. The population of the immunocompetent cells in the cortex of the bursal follicle were denser rather than that of medulla of the bursal follicle. The spleen was surrounded by a thick splenic capsule and there was a small number of trabeculi. The network of the splenic tissue was consisting of a network of reticular cells and fibers and was arranged into red pulps, which were scatteredly distributed within the white pulps. The white pulp was composed of network of reticular cells and reticular fibers within which the immunocompetent cells were diffusely distributed. It contained sheathed arteries and lymphatic nodules. The red pulp of the spleen was formed from venous sinuses and anastomosing cord of reticular cells, macrophages, lymphocytes and blood cells. Cecal tonsil was composed of four histological layers i.e. tunica mucosa, submucosa, muscularis and serosa. Their lining epithelium was simple columnar epithelium. More diffuse lymphoid tissue and unorganized lymphatic nodules were present both in the mucosa and submucosa of the cecal tonsil of broiler. The length and breadth of the thymic lobules were 629.30 ± 118.95 µm and 376.03 ± 98.92 µm, bursal follicles 468.83 ± 52.26 µm and 240.70 ± 34.19 µm, white pulp of the spleen 112.62 ± 13.25 µm and 89.42 ± 12.20 µm, lymphatic nodules of the cecal tonsil 255.20 ± 20.46 µm and 186.08 ± 24.90 µm respectively. The result of the present study revealed that the immunocompetent cells were arranged scatteredly or densely and as unorganized or organized lymphatic nodules in the lymphoid tissues and the length and breadth of the thymic lobule, bursal follicle, splenic white pulp and lymphatic nodule of cecal tonsils were varied within the lymphoid tissues and even one another. Key words: Histology, lymphoid tissues, immunocompetent cells, broilersDOI = 10.3329/bjvm.v4i2.1289Bangl. J. Vet. Med. (2006). 4 (2): 87–92