Video Transcript
The figure shows the structure of
the placenta. Which substance is found in high
concentrations in blood vessel X? (A) Oxygen, (B) glucose, (C)
alcohol, (D) carbon dioxide, (E) amino acids.
This question asks us about an
organ called the placenta, which is a temporary structure formed during
pregnancy. So let’s recall what we know about
the placenta in order to answer this question.
The placenta is responsible for
supplying the developing embryo with oxygen and nutrients while carrying away any
waste products it produces. The placenta is connected to the
developing embryo, which will later turn into a fetus, through a structure called
the umbilical cord.
The umbilical cord contains three
vessels: two arteries and one vein. The arteries carry away blood from
the heart of the developing fetus. These umbilical arteries are
important in fetal development because they transport deoxygenated blood carrying
waste products, such as carbon dioxide. In contrast, the umbilical vein
will carry blood towards the developing fetus. The blood carried by the umbilical
vein contains oxygen and important molecules, such as glucose, to support the
development of the fetus.
Gases and nutrients are exchanged
across the membranes of the chorionic villi, which are fingerlike extensions derived
from the chorionic layer in the fetus. These villi burrow into the
endometrium and form the important membranes for exchange within the placenta.
Now that we’ve reviewed the
structure and the function of the placenta, let’s take another look at our
question. The blood vessel X is pointing to
is one of two vessels represented by a blue color. The blue color indicates that the
vessel is carrying deoxygenated blood. So the vessel we are referring to
must be the umbilical arteries, which carry away waste products like carbon dioxide
away from the developing fetus.
Now that we have reviewed each
structure in our diagram, we can identify the correct answer choice. The substance found in high
concentrations in blood vessel X is carbon dioxide.
