title: Formation of the circle of Willis during human embryonic development.
abstract: The circle of Willis (CW) is a circulatory anastomosis that supplies blood to the brain and adjacent structures. We examined the timing of formation of CW in 20 Japanese human embryo samples by using 3-dimensional reconstruction of serial histological sections. The CW was closed in 1 (n = 6), 2 (n = 8), 2 (n = 3) and 2 (n = 3) samples at Carnegie stages 20, 21, 22, and 23, respectively. The CW was unclosed in 13 samples (unclosed at ACOM alone, 6 samples; ACOM and bilateral P1, 4; left PCOM and right P1, 1; right PCOM and right P1, 1; ACOM and left PCOM, 1). It was difficult to predict whether the circle would close during further development, as such variations frequently exist in adults.
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takakuwa
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Teppei
authors.initials: T
authors.lastname: Koike
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Taiga
authors.initials: T
authors.lastname: Muranaka
authors.affiliation: Congenital Anomaly Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Chigako
authors.initials: C
authors.lastname: Uwabe
authors.affiliation: Human Health Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan.|Congenital Anomaly Research Center, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Shigehito
authors.identifier: http://orcid.org/0000-0002-8194-6927
authors.initials: S
authors.lastname: Yamada
mesh_terms: D002941:Circle of Willis / Q000196:embryology*; D004622:Embryo, Mammalian; D005260:Female; D006801:Humans; D057054:Molecular Imaging; D038081:Organogenesis; D011247:Pregnancy
keywords: circle of Willis; human embryo; three-dimensional reconstruction