Video Transcript
Which of the following products of the bone marrow is found in lymph nodes? (A) White blood cells. (B) Red blood cells. (C) Blood platelets. Or (D) all of the answers are correct.
This question asks us about a product of the bone marrow which is found in the lymph
nodes. Let’s review the key facts about the cells of the bone marrow and the function of the
lymph nodes so we can then answer the question correctly. Bone marrow makes stem cells, which differentiate into red blood cells, platelets,
and white blood cells. All these are answer options for this question. So we will need to look further at lymph nodes and the lymphatic system to come up
with the correct answer.
So what are lymph nodes? You may have noticed some of your own lymph nodes when you were sick. They tend to swell and become painful when your body is fighting an infection. These are small bean-shaped structures that contribute to the immune function of the
lymphatic system. Let’s look at how the lymphatic system carries out its role in immunity.
Blood capillaries have a wall which is just one cell thick. It is leaky, so fluid from the blood leaks out. However, the gaps in the capillary wall are too small for platelets and red blood
cells to pass through, so these remain in the circulatory system. The fluid, called interstitial fluid, fills the gaps around the cells, called the
interstitial space. This means exchange of substances occurs. The cells can receive oxygen and nutrients and get rid of wastes.
About 90 percent of this fluid is reabsorbed by the capillaries. The remaining 10 percent will be taken up by the lymphatic capillaries and is now
called lymph. The lymph is carried by the lymphatic vessels to lymph nodes, which filter it for
cancerous and damaged cells, as well as for pathogens. The lymph nodes contain white blood cells, or leukocytes, leuko- meaning white and
-cyte meaning cell. These include T lymphocytes and B lymphocytes, which produce antibodies. If these cells detect a pathogen, they are able to initiate an appropriate immune
response. Then, the filtered lymph is returned back to the bloodstream via the subclavian vein
found just under the collarbone to circulate around the body again.
After reviewing the cells of the bone marrow in the lymphatic system, we can now
return to our question. The correct answer is (A). The products of the bone marrow found in lymph nodes are white blood cells.
