Video Transcript
Which of the following best
describes lymph? (A) A fluid comprised of waste
products that is transported by lymph vessels to the kidneys to be excreted. (B) A fluid derived from blood
plasma, comprised of water, nutrients, and other biological molecules, that is
transported in lymph vessels. (C) A fluid produced by lymph nodes
that is used to regulate the body’s water content. Or (D) a fluid derived from blood,
comprised of red blood cells, proteins, and platelets, that is transported in lymph
vessels.
To answer this question, let’s
first go over the role of the lymphatic system so we can understand the function and
composition of lymph.
In the body, the circulatory system
is responsible for transporting blood from the heart to the various tissues of the
body, delivering oxygen and essential nutrients to the cells of these tissues via
blood vessels called arteries.
At the body tissues, the arteries
branch into a network of tiny vessels called capillaries, which surround the body
cells. Nutrient-rich fluid is released
from the capillaries into the spaces between the cells, which is called the
interstitial space. Interstitial fluid found in the
interstitial space is derived from blood plasma, the fluid in which blood cells are
suspended. The body cells take up the oxygen
and nutrients they need from the interstitial fluid and release their waste products
back into it.
Most of the interstitial fluid is
absorbed back into the capillaries and is carried toward the heart by larger blood
vessels called veins. A small volume of the fluid remains
in the interstitial spaces. This is taken up by lymph vessels
called lymphatic capillaries. Once interstitial fluid has been
absorbed into the vessels of the lymphatic system, it is referred to as lymph.
Lymph is derived from interstitial
fluid, which in turn is derived from blood plasma. It is 90 percent water and also
contains proteins, fats, salts, and other biological molecules. It can sometimes contain
disease-causing pathogens too.
If we take a look back at our
answer options, using the information that we’ve learned about the composition of
lymph, we can see that the answer that best describes it is (B). Lymph is a fluid derived from blood
plasma, comprised of water, nutrients, and other biological molecules, that is
transported in lymph vessels.
