The spleen is considered a key player in birds’ immunity. The stroma and the parenchyma of the spleen of the adult quail were demonstrated
histologically, histochemically, and ultrastructurally. A thin capsule and the absence of trabeculae were the most characteristics of
spleen stroma. The demarcation between white pulp and red pulp was not observed in the quail. White pulp formed from the periarterial
lymphatic sheath and the periellipsoidal lymphatic sheath, both of which were surrounded by arteriole and ellipsoid, respectively. Ellipsoids
appeared more numerous and were characterized by cuboidal lining of the epithelium and supporting cells. Red pulp consisted of sinuses
and cords. White pulp and red pulp of the quail spleen contained various cells, such as red blood cells, macrophages, heterophils with characteristic
granules, lymphocytes of different sizes, dendritic cells, plasma cells, and telocytes. In addition, closed circulation and open circulation
established the blood flow on the spleen.