Dyshliuk N. Morphogenesis of the esophagus and stomach and their immune formations in the ontogenesis of chickens

Differentiation of the anterior intestine into the esophagus and the stomach began in prefetuses on the 8th day, and from 9th day they were well-defined macroscopically. Crop became noticeable on the 10th day of incubation. The division of the stomach on its parts began on 9th day of incubation. In the wall of esophagus, crop and stomach of chicken fetuses on day 20 of incubation all its structural components inherent to adult birds, (membranes and their layers), were recorded. In the postnatal period of ontogenesis the growth rates of the esophagus and stomach are increased until the end of the first period of oviposition.The morphogenesis of parts of esophagus, crop and stomach was manifested by changes in the parameters of the wall thickness and membrane area that they occupied. Macroscopically, the esophageal tonsil in vaccinated chickens was detected from the age of 10 days, and in non-vaccinated chickens of 15 days. Among the cells of the esophageal tonsil lymphocytes, immunoblasts, proplasmocytes, plasma cells, monocytes, macrophages, reticulocytes, heterophiles, fibroblasts and M-cells were detected. The immune formations of the esophagus, crop and stomach of chickens were represented by lymphoid tissue, which was located in their tunica mucosa. In the stomach wall it was also found in the tunica muscularis and tunica serosa. The development of these formations occured asynchronously. Full morphofunctional maturity of the esophageal tonsil and immune formations of the proventriculus occured in 15-day, crop in 25-day, esophagus in 60-day, the intermediate zone in 90- day chickens.Vaccination of day-old chickens against Marek's disease and infectious bronchitis stimulated the development of the lymphoid tissue of the immune formations of esophagus, crop, esophageal tonsil, proventriculus and accelerated their morphofunctional maturity by 5 days. There were no blood stem cells (CD34^+) in the esophageal tonsil of chickens. In this regard, it can not perform the hematopoietic function. In it only the final differentiation of lymphocytes into effector cells occurs. Among them, lymphocytes with markers CD4^+, CD8+ and CD20^+ were expressed.