Morphohistometric Evaluation of Embryonic Development of Spleen in Chicken

The aim of this study was to evaluate the morphohistometric development of chick spleen by considering specific embryonic periods. For the study, spleens obtained from 18 Babcock White Leghorn chick embryos on the $13^{th}, 16^{th} and 21^{st}$ days of incubation were used. The sections were stained with Crossmon’s trichrome stain and Pappenheim’s panoptic stain and differential leukocyte counts were made in the blood smears. In the measurements, an increase in the spleen volume, embryo weight and vitellus sac weight were determined. There was an increase between the $13^{th}$ and $16^{th}-21^{st}$ days in spleen volume. The highest heterophil granulocytes (74.83%) and lowest lymphocyte ratio (23%) were found on the $21^{st}$ day. On the $13^{th}$ day, there were very few lymphocytes around the vessels. On the 16th day, arteria centralis were frequently encountered and periarteriolar lymphoid tissue formation with lymphocyte accumulations around them started to develop in the spleen parenchyma. The red and white pulp areas could be easily distinguished in splenic parenchyma on the $21^{st}$ day. It was concluded that the structures characterised by lymphocyte infiltrations in the spleen parenchyma were formed and caused changes in the number of lymphocytes in peripheral blood during the embryonal period.