Which tissue is most sensitive to ionizing radiation?

Which tissue is most sensitive to ionizing radiation?

• A. Bone marrow
• B. GI tract
• C. CNS
• D. Skin

Answer: (A)

Radiosensitivity tracks with cell proliferation and differentiation: rapidly dividing, undifferentiated cells are the most vulnerable to ionizing radiation. Bone marrow contains hematopoietic stem and progenitor cells that are constantly dividing to replenish blood cells, so they suffer DNA damage and cell death readily when exposed to radiation. This leads to quick declines in white cells, red cells, and platelets, causing immunosuppression, anemia, and bleeding risk. Because of this, bone marrow is the most sensitive tissue and often the dose-limiting organ in radiation exposure. The GI tract has rapidly renewing mucosa and is also quite sensitive, but not to the same extent as bone marrow. The CNS, composed mainly of mature, non-dividing neurons, is comparatively resistant to acute radiation effects. The skin’s basal cells do turn over, but this tissue is less sensitive than bone marrow in the typical ranking.

Radiosensitivity tracks with cell proliferation and differentiation: rapidly dividing, undifferentiated cells are the most vulnerable to ionizing radiation. Bone marrow contains hematopoietic stem and progenitor cells that are constantly dividing to replenish blood cells, so they suffer DNA damage and cell death readily when exposed to radiation. This leads to quick declines in white cells, red cells, and platelets, causing immunosuppression, anemia, and bleeding risk. Because of this, bone marrow is the most sensitive tissue and often the dose-limiting organ in radiation exposure.

The GI tract has rapidly renewing mucosa and is also quite sensitive, but not to the same extent as bone marrow. The CNS, composed mainly of mature, non-dividing neurons, is comparatively resistant to acute radiation effects. The skin’s basal cells do turn over, but this tissue is less sensitive than bone marrow in the typical ranking.