The deeper the organ, the less it’s affected?
In: Biology
No, they’re not. Different types of body tissue have different levels of sensitivity to radiation. For example, reproductive organs or bone marrow are much more sensitive than skin or liver, for example. When we calculate the risk associated with some dose of radiation, we use what are called sensitivities to take into account the different sensitives. Tissue weighing factors are essentially multipliers that allow us to say “x dose of radiation is 5x more damaging to this type of tissue than this other type of tissue.”
Answer: All DNA is affected by ionizing radiation, regardless of what kind of cell it is in. But, not all cells are equally exposed. Skin cells, being on the surface, are most exposed and most likely to develop mutations as a result. But, they also have active defenses, like producing melanin to try and absorb some of that radiation before it hits the DNA.
UV light does not penetrate very far, so internal organs have zero risk of mutation from UV. But they are at risks from radiation that penetrates more deeply, like X-rays.
Ionizing radation causes damage to the existing DNA, but does not become a mutation until that DNA is copied, and the copy is “incorrect,” with the damage affecting the replication process and so giving a new strand of DNA with a different pattern of nucleotides. So while radation will damage all cell types, the ones that are mostly likely to result in mutations that lead to things like cancer are the cells that divide most often. Skin cells, blood cells, intenstinal linings, lungs, things like that. This is one reason why you never hear about muscle cancer or heart cancer, because while those cells could develop DNA damage, they divide so infrequently that it’s very very rare for that to progress to cause cancerous mutations.
So all cells are vulnerable to ionizing radation if exposed to it, but how likley that it to cause mutation depends on how frequently those cell types replicate.
Is it the deeper the organ, the less effected? Yes, in the sense that the deeper the organ, the more it is shielded by the rest of your tissues in the way, no otherwise.
Are all types of cells equally effected? Yes and no. Yes, ionizing radiation tends to cause the worst damage by damaging DNA specifically; there isn’t cell-specific DNA that is just somehow more resistant to damage*, because it’s just a physical process during exposure. No, because not all cell types are the same, and different morphology can mean they won’t experience the damage the same–in addition, some cell times are long-lived, while others are short-lived, or some that are rapidly dividing. Severe damage to long-lived cells (like nerves) is quite bad. Severe damage to rapidly dividing cells can mean they no longer divide and are just lost. Severe damage to cells that aren’t meant to be around long, can mean they are just replaced without much incident.
*Might be complicated due to a number of biomolecular factors so might not be ‘technically’ true, but as a theme…
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