Question

When and where do chorionic villi appear in humans? State their function.

Answer 1

Hint: The villi are the part of the border between the maternal and the fetal blood. It is the product of conception and plays an important role in pregnancy.

Complete Answer:
Chorionic villi sprout from the chorion. They provide maximum contact area with the mother’s blood. The chorion undergoes various processes for proliferation and absorbs nutrients for the growth of embryos.

It undergoes three stages-
(I) Primary- They contain only trophoblast at this stage. Period of gestation is 13-15 days.
(II) Secondary- It contains trophoblast and mesoderm. Period of gestation is 16-21 days.
(III) Tertiary- It contains trophoblast, blood vessels and mesoderm. Period of gestation is 17-22 days.
- By the end of 2 months, it covers the entire chorion uniformly. It appears just after implantation. They appear as trophoblast and merge with the surrounding uterine tissues and form placenta.
- The villus consists of blood vessels which are present in the connective tissue. The fibroblast mainly forms the connective tissue.

Function:
- It is an important method for prenatal diagnosis.
- The chorionic villi cells are multipotent in nature. They are widely used as stem cells.
- It becomes the fetal part of the placenta through which the exchange of nutrients and waste occurs.

Note: The chorionic villi form the significant portion of placenta. It increases the surface area due to which the products from the mother’s blood reaches the fetus. Choronic villus are very prone to infection and can lead to miscarriage.