Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: neilep on 16/09/2006 20:56:25
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We all shed skin....you're doing it now !...watch out !!..there's goes a flake....
How long does it take for ME to be fully replenished.
When can I stand up and say ' I am not the same person that I was ? '..months ?..years ?...what about internal organs ? presumably they are replenishing too !....I know the stomach lining replenishes at a vastly accelerated rate...but what about my liver ?..kidneys ?..etc etc
Men are the same as women, just inside out !
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I would think that probably the slowest organ to recycle itself is the brain (it was once thought that this did not renew itself at all in adult life, but now there are some question marks as to whether, and to what degree, the brain can grow new cells).
Even slower to replenish itself, although it is not an organ, would I imagine be mineral bone.
George
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This is interesting as I do not know anything about regeneration of actual organs.. Small bits about stem cells, but not organs.. Can one grow a liver say from a stem cell taken from a liver.. would stem cell injections to a sick liver help.. I know a liver can be grown from a small healthy piece.. but could stem cells help accellerate this or help with regeneration. Nasal passage stem cells regenerate themselves so what about boosting growth oth of problems by adding stem cells speed up regeneration of such organ that may need assistance! How long does it take?
Karen
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The liver is one of the easier organs to grow. Don't know that we have yet got to the point of growing from stem cells (although I do understand that there is advanced research into growing teach from stem cells - a byproduct of observation that some cancers actually create teeth where there should be no teeth in the body), but one reason why people are now giving live liver donation is that if you cut the liver in half, the other half will normally regrow.
George
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I heard that, even if liver cells can regrow easily, the organ as a whole doesn't recreate its perfect inner structure, so, if the damage is quite large, regrowing doesn't solve the problem. Is it true?
About brain and other organs which cells don't reproduce, however, I remember that all their inner components are changed in (maximum) a few months; so, we become new a lot of times in our lifes.
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Hi Neil, George, Light arrow! Hmmmm That's interesting!
Hey Neil, I did not know that any of these things actually would regenerate themselves.. Do we actually shed our stomach Lining like our skin leaving the new skin on the inside?
Karen
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quote:
Originally posted by Karen W.
Do we actually shed our stomach Lining like our skin leaving the new skin on the inside?
The intestines, not least the stomach, do a very tough job. Think of what it is we eat (although it is true that we cook our food first to make it more digestible - our ancestors would have had an even tougher time of it). We start by chewing the food to try and break it up a bit (just shows how tough that food is - after all, think of how tough we are, and yet there are animals that eat and digest us). Then the food enters the stomach, which is full of highly corrosive hydrochloric acid, in order to further break down the food. After that, it continues its journey through the intestines, which add all sorts of corrosive chemicals to break down the food (bearing in mind that much of the food will contain very tough materials that are designed to resist environmental damage, including meat that is in essence no different from the human flesh around it), and while it does this, the powerful muscles of the intestines kneed the food to ensure that the corrosive chemicals are thoroughly mixed with the food so they can do their job properly. And, on top of all of this, while the intestines are operating in this chemically hostile environment, they have to be permeable enough to allow the nutrients to be absorbed from the food.
With all of that going on, are you surprised that the cells in the lining of the stomach and intestines do not survive for long, and need to be replaced regularly.
George
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quote:
Originally posted by lightarrow
I heard that, even if liver cells can regrow easily, the organ as a whole doesn't recreate its perfect inner structure, so, if the damage is quite large, regrowing doesn't solve the problem. Is it true?
I do not know how perfect the regrowth is, although I suspect a much more immediate problem is that when a liver is divided up for living donor transplants, to make sure that enough of the existing structure remains in both donor and recipient in order that it can continue to function in the intervening period until it regrows.
http://en.wikipedia.org/wiki/Liver
quote:
The liver is among the few internal human organs capable of natural regeneration of lost tissue; as little as 25% of remaining liver can regenerate into a whole liver again. This is predominantly due to the hepatocytes acting as unipotential stem cells (i.e. a single hepatocyte can divide into two hepatocyte daughter cells). There is also some evidence of bipotential stem cells, called oval cells, which can differentiate into either hepatocytes or cholangiocytes (cells that line the bile ducts).
Living donor liver transplantation is a technique in which a portion of a living person's liver is removed and used to replace the entire liver of the recipient. This was first performed in 1989 for pediatric liver transplantation. Only 20% of an adult's liver (Couinaud segments 2 and 3) is needed to serve as a liver allograft for an infant or small child. More recently, adult-to-adult liver transplantation has been done using the donor's right hepatic lobe which amounts to 60% of the liver. Due to the ability of the liver to regenerate, both the donor and recipient end up with normal liver function if all goes well. This procedure is more controversial as it entails performing a much larger operation on the donor, and indeed there have been at least two donor deaths out of the first several hundred cases. A recent publication has adressed the problem of donor mortality, and at least 14 cases has been found. The risk of postoperative complications (and death) is far greater in right sided hepatectomy than left sided operations
quote:
Originally posted by lightarrow
About brain and other organs which cells don't reproduce, however, I remember that all their inner components are changed in (maximum) a few months; so, we become new a lot of times in our lifes.
Neil asked about cell replacement. Ofcourse, everything exists with structures within structures, and one can look at each level of structure and ask how frequent the replacement of components in structures at this level.
It is certainly true that many of the structures within a cell will be regularly replaced, even as the cell itself stays in place. Whether this can be said of everything within the cell is a more interesting question. Would you think it actually applies to, for instance, the DNA of the cell itself. It is true that the cell has a repair mechanism to replace damaged DNA, but that repair mechanism is imperfect, so would it necessarily wish to function pre-emptively, or is there so much ongoing damage to the DNA that it actually requires the entire DNA to be repaired every few months?
George
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quote:
Originally posted by neilep
We all shed skin....you're doing it now !...watch out !!..there's goes a flake....
How long does it take for ME to be fully replenished.
" Normally a skin cell matures in 21 to 28 days during its passage to the surface where a constant invisible shedding of dead cells, as scales, takes place. "
http://www.psoriasis-association.org.uk/what-is.html
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I would think that probably the slowest organ to recycle itself is the brain (it was once thought that this did not renew itself at all in adult life, but now there are some question marks as to whether, and to what degree, the brain can grow new cells).
Even slower to replenish itself, although it is not an organ, would I imagine be mineral bone.
George
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This is interesting as I do not know anything about regeneration of actual organs.. Small bits about stem cells, but not organs.. Can one grow a liver say from a stem cell taken from a liver.. would stem cell injections to a sick liver help.. I know a liver can be grown from a small healthy piece.. but could stem cells help accellerate this or help with regeneration. Nasal passage stem cells regenerate themselves so what about boosting growth oth of problems by adding stem cells speed up regeneration of such organ that may need assistance! How long does it take?
Karen
-
The liver is one of the easier organs to grow. Don't know that we have yet got to the point of growing from stem cells (although I do understand that there is advanced research into growing teach from stem cells - a byproduct of observation that some cancers actually create teeth where there should be no teeth in the body), but one reason why people are now giving live liver donation is that if you cut the liver in half, the other half will normally regrow.
George
-
I heard that, even if liver cells can regrow easily, the organ as a whole doesn't recreate its perfect inner structure, so, if the damage is quite large, regrowing doesn't solve the problem. Is it true?
About brain and other organs which cells don't reproduce, however, I remember that all their inner components are changed in (maximum) a few months; so, we become new a lot of times in our lifes.
-
Hi Neil, George, Light arrow! Hmmmm That's interesting!
Hey Neil, I did not know that any of these things actually would regenerate themselves.. Do we actually shed our stomach Lining like our skin leaving the new skin on the inside?
Karen
-
quote:
Originally posted by Karen W.
Do we actually shed our stomach Lining like our skin leaving the new skin on the inside?
The intestines, not least the stomach, do a very tough job. Think of what it is we eat (although it is true that we cook our food first to make it more digestible - our ancestors would have had an even tougher time of it). We start by chewing the food to try and break it up a bit (just shows how tough that food is - after all, think of how tough we are, and yet there are animals that eat and digest us). Then the food enters the stomach, which is full of highly corrosive hydrochloric acid, in order to further break down the food. After that, it continues its journey through the intestines, which add all sorts of corrosive chemicals to break down the food (bearing in mind that much of the food will contain very tough materials that are designed to resist environmental damage, including meat that is in essence no different from the human flesh around it), and while it does this, the powerful muscles of the intestines kneed the food to ensure that the corrosive chemicals are thoroughly mixed with the food so they can do their job properly. And, on top of all of this, while the intestines are operating in this chemically hostile environment, they have to be permeable enough to allow the nutrients to be absorbed from the food.
With all of that going on, are you surprised that the cells in the lining of the stomach and intestines do not survive for long, and need to be replaced regularly.
George
-
quote:
Originally posted by lightarrow
I heard that, even if liver cells can regrow easily, the organ as a whole doesn't recreate its perfect inner structure, so, if the damage is quite large, regrowing doesn't solve the problem. Is it true?
I do not know how perfect the regrowth is, although I suspect a much more immediate problem is that when a liver is divided up for living donor transplants, to make sure that enough of the existing structure remains in both donor and recipient in order that it can continue to function in the intervening period until it regrows.
http://en.wikipedia.org/wiki/Liver
quote:
The liver is among the few internal human organs capable of natural regeneration of lost tissue; as little as 25% of remaining liver can regenerate into a whole liver again. This is predominantly due to the hepatocytes acting as unipotential stem cells (i.e. a single hepatocyte can divide into two hepatocyte daughter cells). There is also some evidence of bipotential stem cells, called oval cells, which can differentiate into either hepatocytes or cholangiocytes (cells that line the bile ducts).
Living donor liver transplantation is a technique in which a portion of a living person's liver is removed and used to replace the entire liver of the recipient. This was first performed in 1989 for pediatric liver transplantation. Only 20% of an adult's liver (Couinaud segments 2 and 3) is needed to serve as a liver allograft for an infant or small child. More recently, adult-to-adult liver transplantation has been done using the donor's right hepatic lobe which amounts to 60% of the liver. Due to the ability of the liver to regenerate, both the donor and recipient end up with normal liver function if all goes well. This procedure is more controversial as it entails performing a much larger operation on the donor, and indeed there have been at least two donor deaths out of the first several hundred cases. A recent publication has adressed the problem of donor mortality, and at least 14 cases has been found. The risk of postoperative complications (and death) is far greater in right sided hepatectomy than left sided operations
quote:
Originally posted by lightarrow
About brain and other organs which cells don't reproduce, however, I remember that all their inner components are changed in (maximum) a few months; so, we become new a lot of times in our lifes.
Neil asked about cell replacement. Ofcourse, everything exists with structures within structures, and one can look at each level of structure and ask how frequent the replacement of components in structures at this level.
It is certainly true that many of the structures within a cell will be regularly replaced, even as the cell itself stays in place. Whether this can be said of everything within the cell is a more interesting question. Would you think it actually applies to, for instance, the DNA of the cell itself. It is true that the cell has a repair mechanism to replace damaged DNA, but that repair mechanism is imperfect, so would it necessarily wish to function pre-emptively, or is there so much ongoing damage to the DNA that it actually requires the entire DNA to be repaired every few months?
George
-
quote:
Originally posted by neilep
We all shed skin....you're doing it now !...watch out !!..there's goes a flake....
How long does it take for ME to be fully replenished.
" Normally a skin cell matures in 21 to 28 days during its passage to the surface where a constant invisible shedding of dead cells, as scales, takes place. "
http://www.psoriasis-association.org.uk/what-is.html
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Have any of you got any scars???
why dont they disappear if the skin that we get the scars on isnt their anymore...
I guess scars fade... like tatto's.. But why dont they disappear completely?
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quote:
Originally posted by ScouseLad
Have any of you got any scars???
why dont they disappear if the skin that we get the scars on isnt their anymore...
I guess scars fade... like tatto's.. But why dont they disappear completely?
The surface of the skin is constantly renewed, so a surface scratch will diappear; but a deaper scratch that cuts down into the grwoing layer (i.e. draws blood, since blood is only required by the growing skin) will effect the stem cells that will create the future upper layers of the skin.
George