title: An ultrastructural study of the developing urogenital tract in early human fetuses.
abstract: OBJECTIVE
  This study examines the gonoducts during the ambisexual stage of human fetal development to define their ultrastructural characteristics, including the origin and antomic relationship of the mesonephric and paramesonephric ducts during gonoductal development.
  
  
  METHODS
  The reproductive tracts from five fetuses ranging in gestational age from 35 to 45 days were processed for ultrastructural examination. The developing mesonephric ducts, paramesonephric ducts, and their surrounding mesenchyme were studied with a Phillips 300 transmission electron microscope.
  
  
  RESULTS
  The mesonephric ducts and paramesonephric ducts have distinctive cytoplasmic and cell surface ultrastructural characteristics, as well as different morphologic patterns of epithelial-mesenchymal interaction. Cephalad portions of mesonephric ducts and paramesonephric ducts are separated by mesenchyme, but more caudal aspects move progressively closer until they are juxtaposed but separate.
  
  
  CONCLUSIONS
  Early mesonephric ducts and paramesonephric ducts may be distinguished because of their distinctive ultrastructural features; epithelial-mesenchymal interaction may be important in their differentiation and maintenance; both gonoducts retain their morphologic identity throughout, supporting their separate origins.
authors.affiliation: Department of Pathology, Hutzel Hospital, Detroit Medical Center, MI 48201.
authors.forename: W D
authors.initials: WD
authors.lastname: Lawrence
authors.forename: D
authors.initials: D
authors.lastname: Whitaker
authors.forename: H
authors.initials: H
authors.lastname: Sugimura
authors.forename: G R
authors.initials: GR
authors.lastname: Cunha
authors.forename: G R
authors.initials: GR
authors.lastname: Dickersin
authors.forename: S J
authors.initials: SJ
authors.lastname: Robboy
mesh_terms: D002466:Cell Nucleolus / Q000648:ultrastructure; D002467:Cell Nucleus / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure; D004848:Epithelium / Q000648:ultrastructure; D006801:Humans; D008650:Mesonephros / Q000648:ultrastructure; D008854:Microscopy, Electron; D008938:Mitosis; D014566:Urogenital System / Q000196:embryology* / Q000648:ultrastructure*