Early development of the human mesonephros

摘要

The mesonephrogenic cord disintegrates into approximately 35-40 provesicular cell masses which aie in close contact with the mesonephric (Wolffian) duct (WD) on theii lateral side. Here, the epithelium of the WD is columnar and shares a common basal lamina with the provesicular cell masses. This in turn gives rise to a sickle-shaped pseudostiatified epithelium. The concavity of the sickle is filled by spherical cells, the transition of which into the surrounding connective tissue is continuous,. The sickle is transformed into a distillation flask and becomes separated from the mesonephric duct while the spherical cells maintain a connection to it by a-for the time being-solid outlet pipe,. The columnar epithelium of the mesonephric duct becomes a multilayered cone, whose surface is in contact with the outlet tube. Shortly after, a continuous lumen is formed in the cone and the outlet pipe which is delimited by cells becoming columnar and forming a basal lamina,. The epithelial anlage of the nephron is clearly separated from the surrounding mesenchyma by these processes,. The flask eventually becomes a coipusculum, the outlet pipe a secretory (proximal) as well as collecting tubule, and the cone of the mesonephric duct a mesoureter., The various sections display differentially differentiated epi-thelia that are clearly distinct from each other. The mesoureter behaves differently during differentiation of epi- and paragenitale: in the epigenitale, it is short and runs into the collecting tubules of the nephrons at the lateral side of the convolved tubules, whereas a long mesoureter crosses the dorsal side of the convolved tubules and joins the corresponding collecting tubules at the far end of the mesonephros in the paragenitale.