Chorionic villi 4637996 208778648 2008-04-28T16:20:23Z Billfalls 1865545 /* Development */ Corrected subject-verb agreement and removed misplaced comma in "Tertiary." {{Infobox Embryology | Name = {{PAGENAME}} | Latin = | GraySubject = 12 | GrayPage = 60 | Image = Gray29.png | Caption = Diagram of a transverse section, showing the mode of formation of the [[amnion]] in the [[chick]]. The amniotic folds have nearly united in the middle line. [[Ectoderm]], blue; [[mesoderm]], red; [[entoderm]] and [[notochord]], black. (Villi of chorion labeled at upper left.) | Image2 = Gray31.png | Caption2 = Model of human [[embryo]] 1.3 mm. long. (Villi of chorion labeled at lower right.) | System = | CarnegieStage = | Days = 24 | Precursor = | GivesRiseTo = | MeshName = Chorionic+Villi | MeshNumber = | DorlandsPre = | DorlandsSuf = | }} '''Chorionic villi''' are [[Wiktionary:villus|villi]] that sprout from the chorion in order to give a maximum area of contact with the maternal blood. Embryonic blood is carried to the villi by the branches of the [[umbilical arteries]], and after circulating through the capillaries of the villi, is returned to the embryo by the [[umbilical veins]]. Thus, the villi are part of the border between maternal and fetal blood during pregnancy. ==Development== The [[chorion]] undergoes rapid proliferation and forms numerous processes, the '''chorionic villi''', which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo. They undergo several stages, depending on their composition. {| class="wikitable" | '''Stage''' || '''Description''' || '''Contents''' |- | Primary || The chorionic villi are at first small and non-vascular. || [[trophoblast]] only <ref name=larsen> Larsen, William J. : Human embryology. Sherman, Lawrence S.; Potter, S. Steven; Scott, William J. 3. ed. </ref> |- | Secondary || The villi increase in size and ramify, while the [[mesoderm]] grows into them. || trophoblast and mesoderm <ref name=larsen/> |- | Tertiary || Branches of the [[umbilical vessels]] grow into the mesoderm, and in this way the chorionic villi are vascularized. || trophoblast, mesoderm, and blood vessels <ref name=larsen/> |} Until about the end of the second month of [[pregnancy]] the villi cover the entire chorion, and are almost uniform in size, but after this they develop unequally. ==Relations== The villi can also be classified by their relations: ===Floating villi=== These villi are found floating freely in the intervillous space. They exhibit a bi-layered epithelium consisting of [[cytotrophoblast|cytotrophoblasts]] with overlaying [[syncytium]] ([[syncytiotrophoblast|syncytiotrophoblast]]). ===Anchoring (stem) villi=== These villi act to stablise mechanical integrity of the placental-maternal interface. ==Tissue composition and cell types== The bulk of the villi consist of connective tissues in which blood vessels are found. Most of the cells in the connective tissue core of the villi are fibroblasts. Macrophages known as [[Hofbauer_Cells|Hofbauer cells]] are also present. ==Additional images== <gallery> Image:Gray21.png|Section through the embryo. Image:Gray35.png|Transverse section of a chorionic villus. Image:Gray36.png|Primary chorionic villi. Diagrammatic. Image:Gray37.png|Secondary chorionic villi. Diagrammatic. Image:Gray459.png|Human embryo of about fourteen days, with yolk-sac. </gallery> ==See also== * [[Chorionic villus sampling]] ==References== <references/> ==External links== * http://www.med.umich.edu/lrc/coursepages/M1/embryology/embryo/06placenta.htm {{developmental-biology-stub}} {{Gray's}} {{Embryology}} [[it:Villi coriali]] [[ja:絨毛膜絨毛]] [[sr:Хорионска ресица]]