A child is born without a thymus. Another child has damage to the bone marrow…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A child is born without a thymus. Another child has damage to the bone marrow.
- Which cells are most affected in each child?
- Are these organs primary or secondary lymphoid organs?
- Name two secondary lymphoid organs where mature lymphocytes meet antigens.
- Why is MALT well placed to guard the body?
Need a reminder? The key ideaShow
Innate immunity has four kinds of barriers: physical, physiological, cellular and cytokine. Each barrier acts on the germs that the barrier before it let through, so the shares multiply. The bone marrow and the thymus are the primary lymphoid organs. The spleen, the lymph nodes, the tonsils, Peyer's patches, the appendix and MALT are secondary lymphoid organs.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Without a thymus, the T cells cannot mature. With damage to the bone marrow, all blood cells are affected, including the lymphocytes, and the B cells cannot mature.
Step 2. (b) Both are primary lymphoid organs, where lymphocytes develop and mature.
Step 3. (c) The spleen and the lymph nodes. The tonsils, the Peyer's patches and the appendix are also correct.
Step 4. (d) MALT lies in the lining of the respiratory, digestive and urogenital tracts, which are the main doors by which germs enter. It makes up about half of the lymphoid tissue of the body.
Answer: (a) T cells; B cells and the other blood cells; (b) primary; (c) spleen and lymph nodes; (d) it lies at the doors of entry.
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