Video Transcript
What structures within the heart
control blood flow from the atria into the ventricles? (A) Capillaries, (B) nerves, (C)
stents, (D) valves, or (E) arteries.
To answer this question, let’s
first discuss what atria and ventricles are by looking at a diagram of the
heart. Numbers one and two on our diagram
refer to the right and left atria, or singular atrium. These are the chambers of the heart
that receive blood from veins. Blood is then pumped from the atria
to the ventricles. The right ventricle is labeled as
three and the left ventricle as four in our diagram.
To be efficient, the heart needs
structures which ensure the blood flows through the heart in one direction only. So when the heart contracts, the
blood should flow out of the arteries and not back into the atria. When the heart relaxes, the blood
which is in the arteries should not flow back into the heart. Structures called valves prevent
the backflow of blood. The semilunar valves prevent the
backflow of blood from the arteries into the heart.
The bicuspid valve is situated
between the left atrium and ventricle and prevents the backflow of blood in these
chambers, while the tricuspid valve is located between the right atrium and
ventricle, preventing backflow of blood in these chambers. The bicuspid valve has two flaps,
and the tricuspid valve has three. These flaps are attached to
tendons, which prevent the valves from turning inside out by mistake.
We now have enough information to
answer our question. The structures within the heart
that control blood flow from the atria into the ventricles are named in answer
choice (D), valves.
