Gudz N. The growth and development of cloacal bursa of ducks in postnatal period of ontogenesis

It is well-known that cloacal bursa is always present in ducks from one to 270 days old. The cloacal bursa is registered only in 25 percent of ducks that are 300 days old and completely absent in those that are 330 days old.The form of cloacal bursa in ducks younger than 150 days old is elongated and oval; contrastingly, it has a needle-like shape in older ducks.The growth of duck's cloacal bursa is completed at 60 days old.The structural functional units are known to be found in the mucosa of duck's cloacal bursa up to 180 days old. The findings show that this organ combines the functions of both central and peripheral immune organs.The forming of cloacal bursa as a central immune organ is not finished with the duck's hatching. Its structural units keep with the development of the duck until 30 days old and reach its maximal parameters at 60-90 days old.It is registered that cells in parenchyma of duck's cloacal bursa not only create microenvironment for the lymphocytes development, but also the cells of B-lymphocytopoesis development, granulocytes, macrophages and plasmocytes.The signs of cloacal bursa involution can be determined in ducks older than 60 days old.The structural functional units of parenchyma of cloacal bursa cannot be determined in ducks that are 210 days or older. It indicates that this organ ceases to function before it is completely involution.