title: Embryogenesis of fused umbilical arteries in human embryos.
abstract: OBJECTIVE
  The objective of this study was to elucidate the embryologic basis of fused umbilical arteries in the human.
  
  
  METHODS
  Twenty-nine human embryo specimens at Carnegie stages 11 through 15 (4-5 weeks after fertilization) were examined histologically, with special reference to the development of umbilical arteries.
  
  
  RESULTS
  All embryos at Carnegie stage 11 and 12 had fused umbilical arteries, and 66% of Carnegie stage 13 embryos and 29% of Carnegie stage 14 embryos still had the condition. None of the embryos at Carnegie stage 15 or older had fused umbilical arteries, but there were always 2 arteries present in their umbilical cords.
  
  
  CONCLUSIONS
  Our data suggest that (1) a single umbilical artery splits into 2 as the developmental stage of the embryo advances, (2) that fused umbilical arteries represent a remnant of the embryonic phenotype, and (3) that fused umbilical arteries are embryologically distinct from true single umbilical artery.
authors.affiliation: Congenital Anomaly Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan. shyamada@cac.med.kyoto-u.ac.jp
authors.forename: Shigehito
authors.initials: S
authors.lastname: Yamada
authors.forename: Junzo
authors.initials: J
authors.lastname: Hamanishi
authors.forename: Shozo
authors.initials: S
authors.lastname: Tanada
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Tachibana
authors.forename: Rokuro
authors.initials: R
authors.lastname: Mimura
authors.forename: Shingo
authors.initials: S
authors.lastname: Fujii
authors.forename: Kohei
authors.initials: K
authors.lastname: Shiota
mesh_terms: D002102:Cadaver; D006801:Humans; D014469:Umbilical Arteries / Q000002:abnormalities* / Q000196:embryology*