Video Transcript
The figure shows a fetus developing
in the uterus. What is the name and function of
X? (A) The chorionic fluid that allows
the exchange of materials with the mother. (B) The amniotic fluid that allows
the exchange of materials with the mother. (C) The chorionic fluid that
secretes hormones. (D) The amniotic fluid that
protects the fetus. (E) The amniotic fluid that
secretes hormones.
During conception, a sperm
fertilizes the egg to form the embryo. The cells of the embryo can divide
to eventually form a structure called a blastocyst as we can see here. The blastocyst has an inner cell
mass, which develops into the fetus that we can see on the right. And it also has the trophoblast,
which can develop into the extraembryonic membranes that assist in the development
of the fetus.
There are different types of
extraembryonic membranes. The chorion is the outermost
membrane that surrounds the fetus. It develops fingerlike projections
that interact with parts of the endometrium of the mother to form the placenta. The placenta supplies the fetus
with nutrients and oxygen and carries away waste products from the fetus. It exchanges these materials
through a structure called the umbilical cord that attaches the placenta to the
fetus.
Another extraembryonic membrane
formed from the trophoblast is the amnion. This is the innermost layer that
surrounds the fetus. The amnion is filled with amniotic
fluid. And this acts as a shock absorber
to protect the fetus from fluctuations in temperature, trauma, and sudden sharp
movements. We can see that amniotic fluid is
what the label X is pointing to. Therefore, the correct answer is
(D): the amniotic fluid that protects the fetus.
