Are all cells of the body equally susceptible to radiation?

• A. Yes
• B. No, they are not equally susceptible
• C. Only dividing cells are susceptible
• D. Susceptibility is the same for all ages

Answer: (B)

Radiosensitivity varies among cells; ionizing radiation does not affect all cells equally. Some cells are highly sensitive because they divide rapidly or are immature, such as stem cells and certain mucosal or hematopoietic cells. Others are more resistant, like mature nerve or muscle cells that divide infrequently and have strong DNA repair capabilities. The level of damage depends on factors such as whether cells are actively dividing, their oxygenation level, and where they are in the cell cycle (cells in mitosis are especially vulnerable). Age also matters—developing tissues in children and fetuses tend to be more radiosensitive than adult tissues. Because of these differences, not all cells have the same susceptibility to radiation.