Which statement is true about hematopoietic tissues?

• A. They are highly radiosensitive due to rapid mitotic activity and low differentiation
• B. They are completely radioresistant
• C. They are only radiosensitive at high doses
• D. They have no mitotic activity

Answer: (A)

Radiosensitivity in tissues is highest when cells divide rapidly and are not highly differentiated. Hematopoietic tissues fit this pattern, with continuously renewing, relatively undifferentiated cells. Ionizing radiation damages DNA, and rapidly dividing cells have less time to repair, making them more susceptible to apoptosis or loss of function. That combination—frequent mitosis and low differentiation—explains why hematopoietic tissues are highly radiosensitive and can be affected even at lower radiation doses. This is not the case for completely radioresistant tissues, nor for tissues with no mitotic activity, and sensitivity is not limited to high doses.