Which of the following is not a secondary lymphoid tissue?ANSWERSpleenThymusAppendixI AM UNSURETonsils

To determine which option is not a secondary lymphoid tissue, we need to understand the difference between primary and secondary lymphoid tissues.

1. Primary Lymphoid Tissues: These are the sites where lymphocytes are generated and mature. The main primary lymphoid tissues are the bone marrow and the thymus.

2. Secondary Lymphoid Tissues: These are the sites where lymphocytes become activated and are involved in the immune response. Examples include the spleen, lymph nodes, and mucosal-associated lymphoid tissues such as the tonsils and appendix.

Now let's analyze the options:

• Spleen: This is a secondary lymphoid organ that filters blood and helps in the immune response.
• Thymus: This is a primary lymphoid organ where T-lymphocytes mature.
• Appendix: This is part of the gut-associated lymphoid tissue (GALT) and functions as a secondary lymphoid organ.
• Tonsils: These are also considered secondary lymphoid tissues that help in immune response.

Final Answer

The Thymus is not a secondary lymphoid tissue; it is a primary lymphoid tissue.