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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.
