Chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood. They are an essential element in pregnancy from a

histomorphologic Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...

perspective, and are, by definition, a product of conception. Branches of the umbilical arteries carry embryonic blood to the villi. After circulating through the capillaries of the villi, blood returns to the embryo through the umbilical vein. Thus, villi are part of the border between maternal and fetal blood during pregnancy.

Structure

Villi can also be classified by their relations: * Floating villi float freely in the intervillous space. They exhibit a bi-layered epithelium consisting of

cytotrophoblast "Cytotrophoblast" is the name given to both the inner layer of the trophoblast (also called layer of Langhans) or the cells that live there. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo ...

s with overlaying syncytium (

syncytiotrophoblast Syncytiotrophoblast (from the Greek 'syn'- "together"; 'cytio'- "of cells"; 'tropho'- "nutrition"; 'blast'- "bud") is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nut ...

). * Anchoring (stem) villi stabilize mechanical integrity of the placental-maternal interface.

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 then, they develop unequally.

Microanatomy

The bulk of the villi consist of connective tissues that contain blood vessels. Most of the cells in the connective tissue core of the villi are fibroblasts. Macrophages known as Hofbauer cells are also present.

Clinical significance

Use for prenatal diagnosis

In 1983, an Italian biologist named

Giuseppe Simoni Giuseppe Simoni is an Italian biologist and scientist. He was born in Pavia, Italy in 1944, and obtained his degree in biology at the University of Milan, where he later became a professor of genetics and biology for thirteen year He is currently th ...

discovered a new method of prenatal diagnosis using chorionic villi.

Stem cell

Chorionic villi are a rich source of

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

Biocell Center Biocell Center is an international company specializing in the cryopreservation and private banking of amniotic fluid stem cells. The company is headquartered in Italy with several international locations and is involved with numerous partnerships ...

, a biotech company managed by

, is studying and testing these types of stem cells. Chorionic stem cells, like amniotic stem cells, are uncontroversial multipotent stem cells.

Infections

Recent studies indicate that the chorionic villi may be susceptible to bacterial and viral infections. Recents findings indicate that

ureaplasma parvum ''Ureaplasma parvum'' is a species of ''Ureaplasma'', a genus of bacteria belonging to the family Mycoplasmataceae. In Indonesia, ureaplasma parvum is most commonly contracted through contact with public toilets. ''Ureaplasma parvum'' was former ...

can infect the chorionic villi tissues of pregnant women, thereby impacting pregnancy outcome. DNA from JC polyomavirus and

Merkel cell polyomavirus Merkel cell polyomavirus (MCV or MCPyV) was first described in January 2008 in Pittsburgh, Pennsylvania. It was the first example of a human viral pathogen discovered using unbiased metagenomic next-generation sequencing with a technique called d ...

has been detected in chorionic villi from pregnant women and women affected by

miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the death of an embryo or fetus before it is able to survive independently. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical lo ...

. DNA from BK polyomavirus has also been detected in the same tissues but to a lesser extent.

Early miscarriage

Gross pathology of fixed chorionic villi

In early miscarriage, the finding of chorionic villi in vaginal expulsions is often the only definite confirmation that there was an intrauterine pregnancy rather than an

ectopic pregnancy Ectopic pregnancy is a complication of pregnancy in which the embryo attaches outside the uterus. Signs and symptoms classically include abdominal pain and vaginal bleeding, but fewer than 50 percent of affected women have both of these symptoms. ...

Additional images

File:Chorionic villi - intermed mag.jpg, Micrograph showing chorionic villi. Intermediate magnification. H&E stain. File:Chorionic villi - very high mag.jpg, Micrograph showing chorionic villi. Very high magnification. H&E stain. File:Gray21.png, Section through the embryo. File:Gray35.png, Transverse section of a chorionic villus. File:Gray459.png, Human embryo of about 28 days, with yolk-sac.

References

External links

* http://www.med.umich.edu/lrc/coursepages/M1/embryology/embryo/06placenta.htm Embryology {{Portal bar, Anatomy