Question

Which of the following is NOT a secondary lymphoid organ?

• A. Lymph nodes
• B. Spleen
• C. Peyer’s patches
• D. Bone Marrow

Hint:

Primary = Bone marrow, Thymus Secondary = Spleen, Lymph nodes, Peyer’s patches

Answer 1

The Correct Option is D

Concept: Lymphoid organs are classified into:
• Primary lymphoid organs → Site of lymphocyte formation and maturation
• Secondary lymphoid organs → Site of immune response activation

Step 1: Identify primary organs.

• Bone marrow → Primary lymphoid organ
• Thymus → Primary lymphoid organ

Step 2: Identify secondary organs.

• Lymph nodes → Secondary
• Spleen → Secondary
• Peyer’s patches → Secondary

Step 3: Final conclusion.
Thus, the organ which is not a secondary lymphoid organ is: \[ Bone Marrow \]