Histological Study of the Caecal Tonsil in the Cecum of 4- 6 Months of Age White Leghorn Chicks

Cecum, the largest part of chicken’s large intestine, has an important role in liquid absorption and cellulose digestion. It acts as a defensive organ as well due to the presence of large masses of diffuse and nodular lymphatic tissue in lamina propria and sub mucosa. The cecal tonsil activity has been proved to be depended on the activity of bursa of fabricious and thymus. As the bursa of fabricious and the thymus are exposed to involution through these ages, finding the changes (if any) occur in the caecal tonsil has been our aims. Eighteen (18) healthy white leghorn chickens of 16, 20 and 24 weeks old were selected and fixed the samples of their caecal tonsils, thymuses and bursas of fabricious in 10% buffered formalin, immediately after slaughter. Routine histological laboratory methods were used and 6 µm sections were stained with hematoxylin- eosin staining method and studied under light microscope. The nodular units (ND) width and height, ND fossulae’s lumen width, distribution areas of the lymphatic nodules and crypts of lieberkuhn /mm² in the caecal tonsils, cortices and medullas diameters of the thymuses and the cortices and medullas diameters of lymphatic nodules, heights of plicas and No of nodules/ plica in the bursas of fabricious of all ages were measured and then analyzed with one way ANOVA test. In the cecal tonsils, the most important changes regarding with involution process was significant decline of lymphatic nodules/ mm² of mucosal wall and nodular evacuation at 6 months ones, while thymuses decrease the cortical diameter at 5 months. No significant changes in regarding with involution process were shown in the bursas of fabricious through these ages and no changes in the sub epithelial lymphoid tissues of the cecal tonsils as well. By the results of this study, we come to know that the cecal tonsil growth can be depended on thymus and bursa of fabricious activity, since involution process is first begun in thymus at 5 months of age and then it occurs in thymic dependant areas of the cecal tonsil at 6 months of age. As no involution occurred in bursa of fabricious through these ages, cecal sub- epithelial lymphatic tissue dependant on bursa of fabricious remained unchanged.