Biological Effects of Radiation
Biological Effect
Mechanisms of Damage
Injury to living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionizing radiation causes atoms and molecules to become ionized or excited. These excitations and ionizations can: * Produce free radicals. * Break chemical bonds. * Produce new chemical bonds and cross-linkage between macromolecules. * Damage molecules that regulate vital cell processes (e.g. DNA, RNA, proteins).
The cell can repair certain levels of cell damage. At low doses, such as that received every day from background radiation, cellular damage is rapidly repaired. At higher levels, cell death results. At extremely high doses, cells cannot be replaced quickly enough, and tissues fail to function.
Tissue Sensitivity
In general, the radiation sensitivity of a tissue is: * proportional to the rate of proliferation of its cells * inversely proportional to the degree of cell differentiation
For example, the following tissues and organs are listed from most radiosensitive to least radiosensitive: Most Sensitive: Blood-forming organs | Reproductive organs | Skin | Bone and teeth | Muscle | Least sensitive: Nervous system |
This also means that a developing embryo is most sensitive to radiation during the early stages of differentiation, and an embryo/fetus is more sensitive to radiation exposure in the first trimester than in later trimesters.
Prompt and Delayed Effects Radiation effects can be categorized by when they appear. * Prompt effects: effects, including radiation sickness and radiation burns, seen immediately after large doses of radiation delivered over short periods of time. * Delayed effects: effects such as cataract formation and cancer induction that may appear months or years after a radiation exposure Prompt Effects
High doses delivered to the whole body of healthy adults within short periods of time can produce effects such as
Mechanisms of Damage
Injury to living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionizing radiation causes atoms and molecules to become ionized or excited. These excitations and ionizations can: * Produce free radicals. * Break chemical bonds. * Produce new chemical bonds and cross-linkage between macromolecules. * Damage molecules that regulate vital cell processes (e.g. DNA, RNA, proteins).
The cell can repair certain levels of cell damage. At low doses, such as that received every day from background radiation, cellular damage is rapidly repaired. At higher levels, cell death results. At extremely high doses, cells cannot be replaced quickly enough, and tissues fail to function.
Tissue Sensitivity
In general, the radiation sensitivity of a tissue is: * proportional to the rate of proliferation of its cells * inversely proportional to the degree of cell differentiation
For example, the following tissues and organs are listed from most radiosensitive to least radiosensitive: Most Sensitive: Blood-forming organs | Reproductive organs | Skin | Bone and teeth | Muscle | Least sensitive: Nervous system |
This also means that a developing embryo is most sensitive to radiation during the early stages of differentiation, and an embryo/fetus is more sensitive to radiation exposure in the first trimester than in later trimesters.
Prompt and Delayed Effects Radiation effects can be categorized by when they appear. * Prompt effects: effects, including radiation sickness and radiation burns, seen immediately after large doses of radiation delivered over short periods of time. * Delayed effects: effects such as cataract formation and cancer induction that may appear months or years after a radiation exposure Prompt Effects
High doses delivered to the whole body of healthy adults within short periods of time can produce effects such as