Which of the following is a primary
function of lymph nodes? (A) Lymph nodes circulate the lymph
back to the tissue it came from. (B) Lymph nodes are responsible for
the transport of lymph from tissue to the circulatory system. (C) Lymph nodes are responsible for
initiating an immune response to an infection by a pathogen. Or (D) lymph nodes initiate the
conversion of waste material in the lymph into useful substances.
This question asks us about the
primary function of lymph nodes. Let’s take a look at the lymphatic
system and the role of lymph nodes to figure out the answer. The lymphatic system plays
important roles in the circulatory system and the immune system. In the circulatory system, blood is
pumped from the heart to the different tissues of the body through blood
vessels. When the blood vessels reach the
body tissues, they branch into finer vessels, which are called capillaries. The capillaries form a network
around the cells of the tissues, forming a capillary bed.
Fluid containing oxygen and other
nutrients is released from the capillaries and into the spaces between the
cells. The spaces between the cells are
called the interstitial spaces. The cells take up the oxygen and
nutrients they need and release their waste products back into the interstitial
fluid in these spaces. Most of the interstitial fluid
remaining is then taken up by the capillaries and fed back into the bloodstream to
be returned to the heart. However, a small volume of fluid
remains in the interstitial spaces. The lymphatic system is responsible
for collecting this remaining fluid. This occurs in lymphatic
capillaries, which then drain back into the circulatory system. Once the fluid is taken up by the
lymphatic vessels, it is called lymph.
Lymph contains a lot of water and
carries proteins, fats, and other materials. It might also carry pathogens, for
example, disease-causing microorganisms or viruses, from the tissues. As the lymph travels through the
lymphatic vessels on its way back to the bloodstream, it passes through lymphatic
organs called lymph nodes.
Lymph nodes are small bean-shaped
structures found in groups all over the body. They contain immune cells called
lymphocytes. If the lymph passing through the
lymph nodes contains pathogens, the lymphocytes become activated. They generate an immune response to
the pathogen, destroying or inactivating it. The lymphocytes then exit the lymph
nodes along with the lymph to travel through the bloodstream and attack all other
similar pathogens throughout the body.
If we take a look at the options in
the question, we can see that option (C) correctly outlines the primary function of
lymph nodes in the body. The correct answer is therefore
option (C). The lymph nodes are responsible for
initiating an immune response to an infection by a pathogen.