Types of Chorionic Villi

There two main types of chorionic villi, classified based on their stage of development:

Primary Chorionic Villi

These are the earliest form of villi, appearing around the 5th-6th week of pregnancy. They are finger-like projections that extend from the chorion which is the outermost fetal membrane. They have a simple structure with two cell layers:

Cytotrophoblast: An inner layer of cuboidal cells.
Syncytiotrophoblast: An outer multinucleated layer.

Primary villi lack blood vessels and don’t directly exchange nutrients with maternal blood. Primary villi consist of a central core of mesoderm covered by two layers of trophoblast cells.

Tertiary Chorionic Villi

These are the mature form of villi, developing around the 12th-16th week of pregnancy. They have a much more complex structure than primary villi:

They are branched and highly folded, maximizing the surface area for exchange.
They contain blood vessels from the fetal circulatory system.
They are rich in maternal blood within the intervillous space, allowing for the exchange of gases, nutrients, and waste products.

Chorionic villi are also classified based on their relationship:

Anchoring villi

The specialized chorionic villi are attached and they provide support and stability. They assist in the connection of the placenta to the mother’s uterine wall. They also play a crucial role in the exchange of substances between the fetus and the mother’s blood.

Floating Villi

This type of chorionic villi are present freely in the placenta and are not attached to any part of the placenta i.e. they float in the maternal blood. They are also majorly involved in the nutrient and gas exchange between the fetus and maternal blood.

Chorionic Villi

The chorionic villi, also known as placental villi, are found during pregnancy in females on the placenta. Chorionic villi function to increase the surface area of contact with the maternal blood during pregnancy. During the early weeks of pregnancy, tiny finger-like growths form from the chorion and are called chorionic villi. Understanding chorionic villi types and functions helps medical professionals diagnose and manage pregnancy-related conditions more effectively. In this article, we will cover chorionic villi in detail.

Table of Content

What is Chorionic Villi?
Chorionic Villi Diagram
Types of Chorionic Villi
Chorionic Villi Function
Chorionic Villi Sampling
Stages of Formation of Chorionic Villi
Importance of Chorionic Villi