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Unit 19: Biology Part 2 Page 53 of 137
the heart, these veins, which are
the last ones blood goes through
before re-entering the heat, have
special names. They are called the
superior and inferior vena cava.
Blood returning from an organ in
the top half of the body enters
through the superior vena cava,
while blood coming from the
bottom half uses the inferior vena
cava.
arteries branch off of the aorta, so
they are all carrying oxygen-rich
blood to the various parts of the
body.
Similarly, all of the veins are
carrying oxygen-poor blood back to
the heart. It is only during
pulmonary circulation that oxygen-
poor blood leaves the heart to get
Figure 31 – The superior vena
cava is one of two veins that oxygen, or oxygen-rich blood
bring blood back into the heart. comes back to the heart to be
pumped out to the body. This is a
Once the blood is back in the right good reminder of an important
atrium, the process begins again. point. The heart is not where
blood gets oxygen. It is a pump
Now that we have gone through that sends blood where it needs to
the entire process of both go. It is just a pump, but a very
pulmonary and systemic important one for our survival!
circulation, we can answer the
questions about why the The figure below shows the major
pulmonary artery is the only artery parts of the heart. By now, you
to carry oxygen-poor blood, and should be able to describe what
the pulmonary vein is the only one goes on in each part.
to carry oxygen rich blood. In
systemic circulation, all of the
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