Early development of the human mesonephros.
The mesonephrogenic cord disintegrates into approximately 35-40 provesicular cell masses which are in close contact with the mesonephric (Wolffian) duct (WD) on their 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 pseudostratified 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 corpusculum, 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 epithelia 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.
Ludwig
K S
KS
Department of Anatomy, University of Basel, Pestalozzistr. 20, 4056 Basel, Switzerland.
Landmann
L
L
D018568:Crown-Rump Length; D004626:Embryology; D005260:Female; D005865:Gestational Age; D006801:Humans; D008297:Male; D008650:Mesonephros / Q000196:embryology*; D009399:Nephrons / Q000196:embryology*; D038081:Organogenesis / Q000502:physiology*; D014513:Ureter / Q000196:embryology*; D014928:Wolffian Ducts / Q000196:embryology*