Which of the following tissues is the most radiosensitive?

• A. Cortical Bone
• B. Bone Marrow
• C. Nervous Tissues
• D. Renal Tissues

Answer: (B)

Radiosensitivity tracks with how actively cells are dividing and how undifferentiated they are. Bone marrow has hematopoietic cells that are rapidly dividing to constantly replenish blood cells, so its cells are highly susceptible to radiation damage. In contrast, cortical bone contains mature, less-dividing bone cells in a mineralized matrix, making it relatively resistant. Nervous tissue is made up largely of highly specialized, mostly non-dividing neurons, which also makes it less sensitive than bone marrow. Renal tissue has some turnover but not the same high rate as bone marrow, so it’s not as radiosensitive. Therefore, bone marrow is the most radiosensitive among these tissues.