Gross and histological investigations on the cecum of the black-crowned night heron (Nycticoarx nycticorax)

Abstract

This study was aimed to investigate the gross and the histological structure of the ceca in the black-crowned night heron Nycticoarx nycticorax. Ten captured birds were used in this study. Grossly, the cecum in the night heron was a single left unilateral tube-like (intestinal) structure. It was located at the junction between the small and large intestine, with its pointed free end (the apex) directed cranially. The cecal base possessed a well-developed muscular ring, which may act as a sphincter. Histologically, the mucosa at the proximal region was lined with simple columnar epithelium with few goblet cells. The lamina propria contained a well-developed accumulated lymphoid nodules which either covered with small villi or intermediate villi. The lamina propria and submucosa were infiltrated with the lymphocytes and contained lymphatic nodules extended into the sub mucosa. The cecum possessed a certain pattern of the distribution of lymphatic nodules in the distal rather than that of the proximal regions. The mucosal epithelium at the distal part was hardly observed and the submucosa consisted of dense masses of lymphatic nodules and inter-follicular lymphatic tissues. These extended deeply in the submucosa and contained germinal centers of lymphatic tissues found either deeper and/or closer to the muscular wall, or higher in the lamina propria. The lymphatic nodules and inter-follicular tissues were therefore seemed almost fulfill the entire lumen of the distal part. In conclusion, it was advocated that the ceca of the black crowned night herons may have an important function in immunological responses of the bird against different microorganisms.