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I have been reading about the human liver and zebra fish heart muscle having the ability to regenerate. It seems to me that these organs have very little chance to become damaged or worn out. At the very least their chances of being damaged are comparable to other internal organs. So why those particular organs have the regenerative capability?

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    $\begingroup$ It makes perfect sense for the liver as this is the organ which carries the biggest load in terms of metabolism. The liver is also very important to metabolize a lot of substances that we take up (think of the Cytochrome P450 system). So it is a good idea for this organ to be able to regenerate. $\endgroup$
    – Chris
    Dec 4 '14 at 18:12
  • $\begingroup$ I am unsure of what exactly you are asking. Is your question "Why does the liver regenerate but not other organs?" or "What important organs have the capacity to regenerate?" $\endgroup$ Dec 4 '14 at 20:03
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    $\begingroup$ @anongoodnurse The liver plays a central role in removing toxins. So it can get exposed to a too high dose and suffer damage. See alcoholism for example. You can treat your liver very bad for years and it will still work somehow. $\endgroup$
    – Chris
    Dec 4 '14 at 21:07
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    $\begingroup$ The liver's position in the circulatory system means that it's the first organ hit by toxins absorbed by the intestines (except maybe the intestines themselves). Detoxification of these compounds can involve generation of reactive oxygen species that damage DNA or protein. It doesn't even need to be chronic damage, excessive acetominophen with a little alcohol can destroy a liver pretty quickly. carbon tetrachloride or galactosamine are used to induce liver failure in lab animals. $\endgroup$
    – user137
    Dec 4 '14 at 22:10
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    $\begingroup$ Edited the question again. Thanks for the help Chris Stronks. I was not aware of the damage a liver undergoes and I wanted to ask why internal organs have regenerating capacity at all if they don't wear out. Seems Liver do wear out constantly. $\endgroup$ Dec 5 '14 at 18:36
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It is not really essential that all vital organs should have regenerative potential (for example brain).

The cellular composition of a tissue is a big factor in deciding if the organ/tissue will regenerate or not. Some cells divide while others do not; highly specialized and polarized cells like neurons do not divide perhaps because the act of division itself will compromise their function. That doesn't mean these tissues cannot regenerate; they would need stem cells that can differentiate into the type of cells that died.

So regeneration can happen via:

  • Division of the tissue cells (skin healing, liver regeneration)
  • Differentiation of stem cells (erythropoesis, muscle regeneration)

Organs that do not have non-dividing cells can regenerate by simply proliferating whereas others would need to maintain a stem cell niche- which is not possible in all tissues. Maintenance of stem cells also adds up to the cost of metabolism; so there is some tradeoff.

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