Topography and structural features of esophageal tonsil and stomach lymphoid tissue in ducks

Esophageal tonsil and lymphoid tissue in the stomach of ducks are located locally in the lamina propria and submucosa of the mucus tunic; moreover in gizzard and pyloric part it is situated in the internal layer of muscular tunic and subserous membrane. In esophageal tonsil and proventriculus lymphoid tissue is presented by diffuse lymphoid tissue, prenodules, primary and secondary lymphoid nodules, and in gizzard and pyloric part - only by diffuse lymphoid tissue.