Chorion: Definition & Function Video

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: What Is a Fallopian Tube? - Function, Obstruction & Definition

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:00 Definition
  • 0:53 Chorionic Villi
  • 1:43 Function
  • 2:25 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Derrick Arrington

Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.

During pregnancy, the mother must be connected with the fetus. In this lesson, you will learn about one of the membranes that develops during pregnancy known as the chorion.


A lot of things have to line up for the successful birth of a human child. We usually only think of the development of the fetus itself, but there's a lot happening just outside the fetus too. A big player in the game is the placenta, that circular organ that nourishes the child through the umbilical chord, and the development of the placenta is dependent on the chorion.

The chorion is a membrane that develops at the beginning of a pregnancy between the developing fetus and the mother and continues to grow throughout the pregnancy. It's formed by two layers: the embryonic mesoderm and a double layer of trophoblasts.

  • Mesoderm is one of the primary germ layers of cells that develops at the beginning of embryonic development.
  • Trophoblasts are cells that form the outer layer of the developing embryo and provide nutrients. They also develop into a large portion of the placenta.

Chorionic Villi

As the chorion develops, there are numerous tiny projections that grow out from the chorion known as chorionic villi. If you have had a child recently or know someone who has had a child, you have probably heard of chorionic villi sampling. Chorionic villi sampling (CVS) is a medical procedure often performed on pregnant women after they have been pregnant for around ten weeks.

During this procedure, the doctor inserts a needle into the uterus and removes some of the chorionic villi. Because the villi contains the genetic makeup of the fetus, the doctor can analyze it and inform the parents of numerous chromosomal and developmental issues they might expect with their child such as Down Syndrome or cystic fibrosis. These results may change the way the pregnancy is managed or affect whether the parents want to continue with the pregnancy at all.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account