How the Placenta Nourishes the Fetus

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  • 0:02 Placenta
  • 0:40 Umbilical Cord
  • 1:12 Filtering
  • 1:48 Tranfer of Substances
  • 2:51 Other Functions
  • 3:50 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.

The placenta is a unique organ because it is only present during pregnancy. It nourishes the fetus while it is developing in the womb and is then expelled after the baby is born. Learn how the placenta helps the fetus grow and develop.


Your body contains many organs, like your lungs, stomach, and kidneys. These organs are with you from birth and work hard every day to keep you alive and healthy. But, did you know that when a woman is pregnant, her body creates a new, temporary organ? It's called the placenta, and it's an organ formed in the uterus of a pregnant woman. The placenta helps to nourish the unborn baby, or fetus, as it grows inside the uterus, or womb as it's commonly called. After the baby is born, the placenta is expelled from the woman's body.

Umbilical Cord

The placenta acts as a connection between the mother and the developing fetus. This connection is vital because without a placenta, a fetus would not be able to survive. It's the placenta that supplies the fetus with nutrients and removes wastes produced by the fetus. The actual life line that connects the placenta to the fetus is called the umbilical cord. The mother's blood and the fetal blood never actually mix, so the umbilical cord acts as the transport passageway during the pregnancy.


In a way, you could say that the placenta takes over the responsibilities of some of the fetal organs until they are developed enough to work on their own. For example, the placenta can act like the kidneys. Before blood from the mother goes into the fetus, it passes into the placenta. This blood contains things the fetus needs, like oxygen, glucose and other nutrients. But, it can also contain some substances that could harm the fetus. Fortunately, the placenta acts like a kidney and filters out harmful substances before they reach the fetus.

Transfer of Substances

The placenta also takes over the responsibilities of the lungs until the fetus is ready to be born. When you studied lessons about your lungs and respiratory system, you learned that your lungs breathe in oxygen from the air. This oxygen then gets transferred to your blood and travels all over your body to the body cells. Well, the fetus is inside a watery sac, so its lungs can't breathe in oxygen from the air. Instead, the placenta takes oxygen from the mother's blood and transfers oxygen to the fetus. That oxygen can now be circulated through the blood of the fetus. Just like you, the fetus uses the oxygen and then produces carbon dioxide, which is a waste gas that needs to get out. You expel carbon dioxide through your lungs; in a fetus, the placenta removes carbon dioxide and other waste products. These wastes pass through the umbilical cord and into the placenta. They are then put back into the mother's blood where her system gets rid of them.

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