Sensitivity of human organs or tissues to ionizing radiation

Relative radiosensitivity	Organ or tissue
Very high	Embryonic tissue, lymphoid organs, bone marrow, blood, testes and ovaries, small intestines
High	Skin, lens and cornea of eye, most gastrointestinal organs (oral cavity, esophagus, stomach, rectum), bladder, uterus
Medium	Growing cartilage, growing bones, blood vessels
Low	Mature cartilage or bone, pituitary gland, lungs, thyroid, pancreas, kidneys, adrenal glands
Very low	Brain, spinal cord, muscles

Data from: Rubin P, Casarett GW. Clinical Radiation Pathology. Philadelphia; W.B. Saunders; 1968.

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