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What about the radiation effects at the organ level?

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This particular diagram nicely pictures what happens if the entire organ is exposed

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to radiation. If the entire organ is exposed to radiation, there are two scenarios

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can happen. One is if the dose is very high,

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the organ dies. That leads to death.

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On the other hand, if the radiation is less than very high dose, the organ will try

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to heal. And the healing process can be looked in two different ways.

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One is called the repair mechanism, the other one is called the regeneration

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mechanism. Let's examine the repair mechanism.

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In the repair mechanism, the replacement of damaged cells by different cell type

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will happen.

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And even though the organ not return to its pre-irradiated state, it is repaired,

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so therefore, the organ is not appears exactly like the previous one.

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It has its mark of the radiation exposure, and you can see the healing as

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repaired, but it is not completely brought to the original status.

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This type of repair mechanism occurs in radioresistant tissues, such as muscles and

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CNS, where it can try to repair itself, even though the repair can result

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to the organ not to the original form, but at least it survived.

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The second type of healing is called the regeneration.

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The regeneration mechanism basically replaces the damaged cells by the

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same cell type. Because of that, the organ returns to the

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pre-irradiated state. The radiosensitive tissues undergo this type of

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regeneration, such as skin, bone marrow, and GI tract.

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When they're healing, they try to regenerate, and it shows up as if nothing has

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happened. It brings it back to the original pre-irradiated state.