Template:Spleen Timeline Table
|Carnegie stage 14 to 17
appears as a bulge in the dorsal mesogastrium. Mesothelium pseudostratified.
|Mesothelium (pseudostratified} replaced with high columnar cells and then low columnar cells.|
|Basement membrane present after this stage.|
|Hematopoietic cells detected.|
|Spleen is now apparent. Mesenchymal cells differentiated from cells in dorsal mesogastrium. Sinus and hilus formation after this stage.|
|Arteries and veins parallel entries at this stage.|
|reticulum cells (alpha-smooth muscle actin-positive) scattered around the arterioles|
|reticulum cells increase in number and began to form a reticular framework.|
Accumulation of T and B lymphocytes within this framework, and a primitive white pulp was observed around the arterioles.
|reticular framework antigenic diversity, and T and B lymphocytes were segregated in the framework.|
T lymphocytes were sorted into the alpha-SMA-positive reticular framework, and the periarteriolar lymphoid sheath (PALS) was formed around the arteriole.
B lymphocytes aggregated in eccentric portions to the PALS and formed the lymph follicle (LF, reticular framework alpha-SMA-negative).
|marginal zone appears in reticular framework around the white pulp.|
|Human embryonic data and fetal data  Links: spleen | Kyoto Collection | Timeline human development|
- Endo A, Ueno S, Yamada S, Uwabe C & Takakuwa T. (2015). Morphogenesis of the spleen during the human embryonic period. Anat Rec (Hoboken) , 298, 820-6. PMID: 25403423 DOI.
- Satoh T, Sakurai E, Tada H & Masuda T. (2009). Ontogeny of reticular framework of white pulp and marginal zone in human spleen: immunohistochemical studies of fetal spleens from the 17th to 40th week of gestation. Cell Tissue Res. , 336, 287-97. PMID: 19255788 DOI.