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Which of the following is considered a primary lymphoid organ?

a) Bone marrow.
b) Lymph nodes.
c) Peyer's patches.
d) Spleen.
e) Tonsils.

1 Answer

4 votes

Final answer:

The correct answer is a) Bone marrow, which is considered a primary lymphoid organ where B cells mature and all lymphocytes are initially produced.

Step-by-step explanation:

The primary lymphoid organ mentioned in the options provided is a) Bone marrow. Primary lymphoid organs are where lymphocytes, such as B cells and T cells, are produced and undergo maturation. The bone marrow is the site where all lymphocytes are produced initially. B cells mature here, and while T cells are also produced in the bone marrow, they travel to the thymus to mature, which is also considered a primary lymphoid organ. In contrast, secondary lymphoid organs, such as lymph nodes, spleen, and tonsils, are involved in filtering lymph and storing lymphocytes; they are sites where pathogens encounter and activate lymphocytes, which initiates adaptive immune responses.

Therefore, the correct answer is "a) Bone marrow".

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