Video Transcript
Why do veins often contain
valves? (A) To keep blood moving at a high
pressure. (B) To ensure that blood is able to
clot properly. (C) To prevent blood from becoming
deoxygenated. (D) To prevent the backflow of
blood. Or (E) to keep blood moving against
the concentration gradient.
In your body, blood is pumped by
the heart and circulated through a network of blood vessels, which form the
circulatory system. The flow of blood delivers
molecules like oxygen and nutrients to the organs of your body and carries away the
waste products they generate. This helps every organ in your body
function normally, keeping you healthy. The circulatory system is described
as a closed loop. This means that blood flows in a
closed circuit from the heart to the various organs of the body and back to the
heart. Arteries are the blood vessels that
carry blood away from the heart, while veins are responsible for carrying blood away
from the organs and back towards the heart.
It is extremely important that as
blood flows around the body, its direction does not reverse. In arteries, the pumping pressure
of the heart prevents blood from flowing in the wrong direction. Veins, however, are further away
from the heart, which means they have lower blood pressure within them. To prevent blood from flowing in
the wrong direction, veins have special structures called valves at regular
intervals. These valves only permit the flow
of blood in one direction, ensuring blood continues to circulate correctly.
If we take a look at the options
provided in the question, we can see that the correct answer is option (D): to
prevent the backflow of blood.
