Which tissue is among the most radiosensitive?

• A. Cortical bones
• B. Nervous tissues
• C. Renal tissues
• D. Bone marrow

Answer: (D)

Radiosensitivity reflects how readily cells in a tissue are damaged by radiation, which is greatest in cells that divide quickly and are less differentiated. Bone marrow fits this perfectly: it contains hematopoietic stem cells that are constantly proliferating to produce blood cells, so they’re highly susceptible to radiation damage. That rapid division means DNA is frequently exposed to radiation effects, leading to bone marrow suppression as a common consequence of exposure. In contrast, nervous tissue is made up mostly of mature, non-dividing neurons, making it far less radiosensitive; cortical bone has very low cellular turnover and is relatively resistant; renal tissue has some turnover but not to the same extent as bone marrow.