Chorionic villi

Infobox Embryology
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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.)


Caption2 = Model of human embryo 1.3 mm. long. (Villi of chorion labeled at lower right.)
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Chorionic villi are 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.

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 cytotrophoblasts with overlaying syncytium (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 are also present.

=Additional

ee also

* Chorionic villus sampling

References

External links

* http://www.med.umich.edu/lrc/coursepages/M1/embryology/embryo/06placenta.htm