All of the following cells are produced in the bone marrow, except which one?

All of the following cells are produced in the bone marrow, except which one?

• A. Erythrocytes
• B. Eosinophils
• C. Neutrophils
• D. Lymphocytes

Answer: (D)

The main idea is that bone marrow is the production site for most blood cells, with different lineages doing their maturation there. Erythrocytes (RBCs) come from the erythroid lineage in the marrow, while neutrophils and eosinophils come from the myeloid lineage and complete their development there as well. Lymphocytes, however, come from the lymphoid lineage and mature primarily in other lymphoid tissues—the thymus for T cells and lymph nodes/spleen for B cells (and NK cells). Because their mature development occurs outside the bone marrow, lymphocytes are not produced in the bone marrow in the same sense as the other three options. So the best answer is the lymphocytes.

The main idea is that bone marrow is the production site for most blood cells, with different lineages doing their maturation there. Erythrocytes (RBCs) come from the erythroid lineage in the marrow, while neutrophils and eosinophils come from the myeloid lineage and complete their development there as well. Lymphocytes, however, come from the lymphoid lineage and mature primarily in other lymphoid tissues—the thymus for T cells and lymph nodes/spleen for B cells (and NK cells). Because their mature development occurs outside the bone marrow, lymphocytes are not produced in the bone marrow in the same sense as the other three options. So the best answer is the lymphocytes.