The human placenta

Published on June 30, 2024   44 min

A selection of talks on Reproduction & Development

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0:00
My name is Eric Jauniaux. I'm a professor at the Elizabeth Garrett Anderson Institute for Woman's Health at University College London. It's my pleasure and honour to present this lecture on the human placenta.
0:19
The placenta is characteristic of the mammal species called the placentals. Basically, to simplify things, without a placenta, we would not exist.
0:30
The placentas probably originated after the significant extinction of the Cretaceous-Paleogene 66 to 65 million years ago. That's when the mammals appeared and that's when the placenta started to appear.
0:46
The first thing we're going to do, and which will be the main part of my presentation, is to describe how normal placentation takes place in humans and at the end I will present a few cases where this phenomenon, this process, is abnormal.
1:04
The first week is a week when the first placental tissue appears under the terminology trophectoderm. It's the progenitor tissue of the entire outer epithelial component of the placenta which is going to become the trophoblast. As you can see in these images, the trophectoderm is basically the first tissue to appear in the embryo in the periphery of the blastocyst here on day five post-conception.
1:32
Then the trophectoderm will start developing and it's absolutely essential because it mediates the opposition and the adhesion of the blastocysts to the uterine epithelium. As you can see from the diagram, migrating down the tube is the fertilized egg. When it reaches day five which is approximately when it reaches the uterine cavity, we'll have the trophectoderm, which is an essential part of its attachment to the uterine epithelium. Which in most cases, 99% of the time, is in the upper part of the uterus. Low implantation can also happen in humans and it's called a placenta previa, in which case the blastocyst implants in the lower part of the uterus next to the cervix.

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