Template:Spleen Timeline Table

From Embryology
Human Spleen Development
Embryonic Week
Carnegie Stage
Week 5
Carnegie stage 14 to 17

appears as a bulge in the dorsal mesogastrium. Mesothelium pseudostratified.

Week 6
Mesothelium (pseudostratified} replaced with high columnar cells and then low columnar cells.
Basement membrane present after this stage.
Week 7
Hematopoietic cells detected.
Week 8
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.
Fetal Week FA
Gestational Age GA
Week 15
Week 17
reticulum cells (alpha-smooth muscle actin-positive) scattered around the arterioles
Week 18-21
Week 20-23
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.
Week 22
Week 24
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).
Week 24
Week 26
marginal zone appears in reticular framework around the white pulp.
Human embryonic data[1] and fetal data [2]   Links: spleen | Kyoto Collection | human timeline
  1. 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.
  2. 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.