Body Structures of Gestation: Medical Terminology

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  • 0:00 Gestation
  • 0:27 Chorion & Placenta
  • 1:23 Umbilical Cord
  • 2:06 Afterbirth
  • 2:20 Amnion
  • 3:21 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

As a child develops inside the mother's womb, it's nourished and protected. Learn about structures such as the chorion, amnion, amniotic sac, amniotic fluid, placenta and umbilical cord, and the roles they play during gestation.


As a mom, I can tell you that pregnancy is a time when the emotional connections begin to form between a mother and child. Yet, emotions are not the only bonds that form between mom and baby; there's also a physical joining as the developing child taps into the nutrient supply of the mother. In this lesson, we'll look at the terms used to describe the structures that develop during gestation, which is the developmental time between conception and birth.

Chorion & Placenta

As you know, developing babies aren't covered by a shell, like the hard white shells that protect a baby chicken as it develops.

However, a developing embryo, which is the name given to the unborn child in its earliest stages of development within the womb, does have a couple of membranes covering it. The outermost membrane that surrounds the embryo is referred to as the chorion. As the chorion develops, it produces projections called villi. A good way to think of chorionic villi is as tiny vascular fingers that reach out and connect with the mother's blood supply.

Because the chorion provides a connection with the mother, we see that it contributes to the formation of the placenta, which is actually a temporary organ that develops during pregnancy to transfer oxygen, nutrients and wastes between mother and developing child.

Umbilical Cord

As the pregnancy progresses, we see the development of a flexible tube that attaches the developing child to the placenta. This tube is called the umbilical cord. Since the developing baby cannot eat or breathe on its own, the umbilical cord is truly a lifeline.


However, when the baby arrives into the world, it can take care of eating, drinking, breathing and pooping on its own, so the umbilical cord is no longer needed. The doctor, or father, cuts the cord shortly after birth, leaving behind a tiny stump that dries up and falls off within a few weeks. The remaining scar becomes a belly button, or navel, as it's sometimes called.


With the umbilical cord cut, the placenta no longer has a function and is expelled from the body. The placenta and related membranes that are expelled after the baby is born are referred to simply as the afterbirth.


I mentioned that membranes are part of the afterbirth. We already discussed one membrane, which was the chorion. There's another membrane that lies inside the chorion. This innermost membrane that surrounds the embryo is called the amnion. The amnion is filled with fluid called amniotic fluid, which holds the developing child in a suspended state. So, I guess you could say we all started out life underwater.

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