Chorionic villi are villi that sprout from the chorion

Chorion

The chorion is one of the membranes that exist during pregnancy between the developing fetus and mother. It is formed by extraembryonic mesoderm and the two layers of trophoblast and surrounds the embryo and other membranes...

 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.

In 1983 an italian biologist named Giuseppe Simoni

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 years....

 discovered a new method of prenatal diagnosis using chorionic villi.

Development

The chorion

Chorion

The chorion is one of the membranes that exist during pregnancy between the developing fetus and mother. It is formed by extraembryonic mesoderm and the two layers of trophoblast and surrounds the embryo and other membranes...

 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.

Stage

Description

Period of gestation

Contents >- | Primary

The chorionic villi are at first small and non-vascular.

End of 4th week

trophoblast Trophoblast Trophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...  only >- | Secondary

The villi increase in size and ramify, while the mesoderm Mesoderm In all bilaterian animals, the mesoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and endoderm , with the mesoderm as the middle layer between them.The mesoderm forms mesenchyme , mesothelium, non-epithelial blood corpuscles and...  grows into them.

5th week

>- | Tertiary

Branches of the umbilical vessels grow into the mesoderm, and in this way the chorionic villi are vascularized.

5th - 6th week

trophoblast, mesoderm, and blood vessels

Until about the end of the second month of pregnancy

Pregnancy

Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 the villi cover the entire chorion, and are almost uniform in size, but after this they develop unequally.

Floating villi

These villi are found floating freely in the intervillous space. They exhibit a bi-layered epithelium consisting of cytotrophoblast

Cytotrophoblast

The cytotrophoblast is the inner layer of the trophoblast, interior to the syncytiotrophoblast in an embryo.Cytotrophoblast is considered to be the trophoblastic stem cell; it differentiates into the other forms of trophoblastic tissue .-External links: - "Female Reproductive System: placental...

s with overlaying syncytium

Syncytium

In biology, a syncytium is a large cell-like structure; filled with cytoplasm and containing many nuclei. Most cells in eukaryotic organisms have a single nucleus; syncytia are specialized forms used by various organisms.The term may also refer to cells that are connected by specialized membrane...

 (syncytiotrophoblast

Syncytiotrophoblast

Syncytiotrophoblast is the epithelial covering of the placenta villous tree. It is a unique tissue in that it is a multi-nucleated, terminally differentiated syncytium, extending to 13m^2...

).

Anchoring (stem) villi

These villi act to stabilise 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.

Stem cell

Chorionic villi are rich of stem cells: Biocell Center

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 and research studies of amniotic fluid stem...

, a biotech company managed by Giuseppe Simoni

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 years....

 and based also in Medford, MA, is studying and testing these types of stem cells.
Chorionic stem cells, like amniotic stem cells

Amniotic stem cells

Amniotic stem cells are multipotent stem cells of mesenchymal origin extracted from amniotic fluid.Amniotic stem cells are able to differentiate into various tissue type such as skin, cartilage, cardiac tissue, nerves, muscle, and bone, and may have potential future medical applications.All over...

, are multipotent stem cells without any ethical problem and now it's possible to criopreserve amniotic stem cell for autologous use .

External links

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