{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,22]],"date-time":"2025-10-22T03:05:12Z","timestamp":1761102312972,"version":"build-2065373602"},"reference-count":26,"publisher":"Wiley","issue":"8","license":[{"start":{"date-parts":[[2018,3,9]],"date-time":"2018-03-09T00:00:00Z","timestamp":1520553600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["24119002","26220004","15H01119","15K08134","15H05270","15H01121","16K15535","17H05294","15K15014"],"award-info":[{"award-number":["24119002","26220004","15H01119","15K08134","15H05270","15H01121","16K15535","17H05294","15K15014"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["The Anatomical Record"],"published-print":{"date-parts":[[2018,8]]},"abstract":"<jats:title>ABSTRACT<\/jats:title><jats:p>Variations of the circle of Willis (CW) influence blood supply to the brain and adjacent structures in adults. We examined the formation of the CW in 20 human embryo samples at the end of the embryonic period using 3\u2010D reconstructions of serial histological sections. The CW was closed in all samples, and did not form in a single plane, but was composed of multiple stair\u2010like planes. The artery acutely curved at the caudal part of the CW, namely, at the inlet of the basilar artery and bifurcation of the P1 segment of the posterior cerebral artery (PCA), reflecting flexure of the mesencephalon and diencephalon at this stage. Variations were observed in 17 of 20 samples\u2014only anterior parts (anterior communicating artery [Acom] and anterior cerebral artery [ACA]) in 10 samples, only posterior parts (posterior communicating artery [Pcom]) in one sample, and both anterior and posterior parts in six samples. Variations included the Acom formed as partially duplicated in three samples, duplicated in four, plexiform in three, and no channel as a result of a single azygos ACA in one. The ACA formed as duplicated in two, median ACA in two, and right hypoplasia in one. The Pcom formed in hypoplasia of either side in six samples. Variations observed in this study are similar to those observed in fetuses, neonates, and adults. The P1 segment of PCA was very large in all samples. The present observations indicate that variations in the CW are present from the initiation of CW formation. Anat Rec, 2018. \u00a9 2018 Wiley Periodicals, Inc.<\/jats:p>","DOI":"10.1002\/ar.23794","type":"journal-article","created":{"date-parts":[[2018,2,21]],"date-time":"2018-02-21T13:25:41Z","timestamp":1519219541000},"page":"1312-1319","source":"Crossref","is-referenced-by-count":12,"title":["Variations of the Circle of Willis at the End of the Human Embryonic Period"],"prefix":"10.1002","volume":"301","author":[{"given":"Kana","family":"Furuichi","sequence":"first","affiliation":[{"name":"Human Health Science, Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Aoi","family":"Ishikawa","sequence":"additional","affiliation":[{"name":"Human Health Science, Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Chigako","family":"Uwabe","sequence":"additional","affiliation":[{"name":"Congenital Anomaly Research Center, Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Haruyuki","family":"Makishima","sequence":"additional","affiliation":[{"name":"Congenital Anomaly Research Center, Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8194-6927","authenticated-orcid":false,"given":"Shigehito","family":"Yamada","sequence":"additional","affiliation":[{"name":"Human Health Science, Graduate School of Medicine Kyoto University Kyoto Japan"},{"name":"Congenital Anomaly Research Center, Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9660-9384","authenticated-orcid":false,"given":"Tetsuya","family":"Takakuwa","sequence":"additional","affiliation":[{"name":"Human Health Science, Graduate School of Medicine Kyoto University Kyoto Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2018,3,9]]},"reference":[{"key":"e_1_2_6_2_1","doi-asserted-by":"publisher","DOI":"10.1001\/archneurpsyc.1959.02340160007002"},{"key":"e_1_2_6_3_1","doi-asserted-by":"publisher","DOI":"10.1159\/000149906"},{"key":"e_1_2_6_4_1","first-page":"357","article-title":"Sur la Signification morphologique des arteres cerebrales","volume":"21","author":"Vriese B.","year":"1904","journal-title":"Arch Boil"},{"key":"e_1_2_6_5_1","doi-asserted-by":"publisher","DOI":"10.1186\/1471-2377-6-22"},{"key":"e_1_2_6_6_1","first-page":"99","article-title":"The circle of Willis: anatomical variations","volume":"2","author":"Fisher CM.","year":"1965","journal-title":"Vasc Dis"},{"key":"e_1_2_6_7_1","first-page":"481","article-title":"Morphological examination of the circulus arteriosus cerebri humani (circle of Willis). 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