# Natural regeneration of body parts in humans **URL:** \ **Category:** Factual Questions\ **Created:** [January 14, 2017, 5:26pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126 "2017-01-14T17:26:05Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Mangosteen](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)\ **Post date:** [January 14, 2017, 5:26pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/1 "2017-01-14T17:26:05Z")
I’ve heard that large bones in the human body are naturally completely replaced (regenerated) every 10 or 15 years meaning the bone in your arm today is not the same one you had 10 or 15 years ago. And that these large bones take the longest to regenerate of all other body parts. Organs such as the heart or lungs take a much shorter time to regenerate. Is there a chart that shows how long each body part takes to renew itself? I’m trying to tell a friend that if she would just quit smoking today, in X number of years she would have essentially a new set of lungs. ---
**Author:** ![Monimonika](https://avatars.discourse-cdn.com/v4/letter/m/85e7bf/32.png) [@Monimonika](https://boards.straightdope.com/u/Monimonika)\ **Post date:** [January 14, 2017, 6:13pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/2 "2017-01-14T18:13:10Z")
IANAD, nor very medically knowledgeable, but even with the assumption that parts of the body replace their cells completely by certain intervals of time, it needs to be understood that this a bit-by-bit process. That means that when one cell dies and is replaced with another cell, that new cell has to conform at least somewhat to the other surrounding cells. So, the implication of “no lingering damage” due to “a new set of lungs” may not be accurate. Permanent scars are examples of regeneration/replacement of cells being unable to completely fix past damages. > **[Why are scars permanent?](https://www.nbcnews.com/id/wbna3076698)** > > Every scar tells about the body’s amazing, but not perfect, ability to heal. ---
**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\ **Post date:** [January 14, 2017, 6:32pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/3 "2017-01-14T18:32:42Z")
I’ve heard something about “stem cells” being able to get body parts to re-grow? I wonder if that would include teeth? Anyway as I heard it, stem cells are injected into your bone marrow? I don’t know if that is correct? ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [January 14, 2017, 7:50pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/4 "2017-01-14T19:50:54Z")
Your bone marrow has hemapoietic stem cells. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [January 14, 2017, 8:37pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/5 "2017-01-14T20:37:58Z")
[Young children can regrow fingertips](http://www.npr.org/sections/health-shots/2013/06/10/190385484/chopped-how-amputated-fingertips-sometimes-grow-back). ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [January 14, 2017, 11:02pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/6 "2017-01-14T23:02:21Z")
> [@Mangosteen](#): > > I’m trying to tell a friend that if she would just quit smoking today, in X number of years she would have essentially a new set of lungs. If this is true, then why do ex-smokers have much higher risks of lung cancer than nonsmokers? Why are there any diseases associated with age and aging, for that matter? I suspect strongly that your claim isn’t true, or is in no way true the way you think it is. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [January 14, 2017, 11:07pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/7 "2017-01-14T23:07:05Z")
I think that in most cases, it is the cells already there that create the replacements. If that is the case and your cells already have damaged DNA, so will their replacements. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [January 15, 2017, 1:21am UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/8 "2017-01-15T01:21:05Z")
> [@Mangosteen](#): > > I’m trying to tell a friend that if she would just quit smoking today, in X number of years she would have essentially a new set of lungs. Sorry, that’s not how it works. Lungs can clean up some of the damage and debris from years of smoking, but they do not regenerate. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [January 15, 2017, 6:01am UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/9 "2017-01-15T06:01:24Z")
If the OP is correct, I should be looking forward to a new heart, pancreas, kidneys and eyes. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [January 15, 2017, 6:31am UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/10 "2017-01-15T06:31:29Z")
The brain was long thought to be non-regenerating. Now we are certain that the hippocampus (memory) and olfactory bulbs and a few more are at least regenerating constantly. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 15, 2017, 3:22pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/11 "2017-01-15T15:22:54Z")
> [@Mangosteen](#): > > … > > I’m trying to tell a friend that if she would just quit smoking today, in X number of years she would have essentially a new set of lungs. > [@Qadgop\_the\_Mercotan](#): > > Sorry, that’s not how it works. Lungs can clean up some of the damage and debris from years of smoking, but they do not regenerate. In a context different than OP, that sentence can be used for the old[Ship of Theseus](https://en.wikipedia.org/wiki/Ship_of_Theseus) joke: if lungs and everything else “regenerate” over time–what do they say, we each have a complete turnover of cells every seven years?–I’m not the same I after that period, therefore all my I.O.U.'s are moot. ---
**Author:** ![Kimera757](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kimera757/32/3765_2.png) [@Kimera757](https://boards.straightdope.com/u/Kimera757)\ **Post date:** [January 15, 2017, 3:34pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/12 "2017-01-15T15:34:19Z")
> [@Exapno\_Mapcase](#): > > If this is true, then why do ex-smokers have much higher risks of lung cancer than nonsmokers? > > Why are there any diseases associated with age and aging, for that matter? DNA changes, including the breakdown of telomeres. Every time a eukaryotic cell replicates we lose a bit of DNA from the end of the chromosome. Fortunately telomeres, at the end, are just “junk DNA”. Eventually the telomeres wear away entirely, after about 50-70 cell replications, at which point coding DNA is damaged, and the cell reaches senescence. An aging cell essentially poisons other cells around them. This is probably why the brain “ages”; while many neural cells never replicate, they are supported by glia (“nurse cells”) which do age. Supposedly many of the cell replication mechanisms are near the telomeres on at least one chromosome, so when those telomeres break down the cell can ironically become “immortal”, replicating out of control. Anything that damages DNA can cause cancer, not just aging cells. Worse, that DNA damage sticks around. Stopping smoking would “stop the bleeding” but already-damaged cells would still replicate. I believe some cells in the human body produce a limited amount of telomerase, extending the number of replications before they reach senescence. Cells such as those that line your stomach. Only germ line cells produce enough telomerase to never reach senescence. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [January 15, 2017, 7:31pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/13 "2017-01-15T19:31:37Z")
> [@barbitu8](#): > > Your bone marrow has hemapoietic stem cells. IIRC, stem cells other than hemapoietic, have been obtained from bone marrow. Perhaps Qadgop the Mercotan can comment on this. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [January 15, 2017, 7:47pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/14 "2017-01-15T19:47:17Z")
The liver is the only organ that can truly regenerate itself. It is possible to lose over 75% of it and have it grow right back (not recommended but completely possible). It would be great if other organs could do that in the future. Maybe a breakthrough in stem cell research or something like it will enable that to happen in our lifetime but it isn’t the case right now. I think the OP is talking about something very different than true “regeneration”. Cell exchange may be a better term but that isn’t regeneration. If you remove parts of other organs like the lung, brain or heart, they may heal and even become more functional but they won’t truly regenerate. The parts that are removed are gone for good. The OP may be talking about the rate that cells die and are replaced in different parts of the body but that is not the same as regeneration. The new cells generally just take the place of worn out ones. The newer generation is the same with slightly more worn out DNA. That is one of the keys to aging process. ---
**Author:** ![Anaglyph](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@Anaglyph](https://boards.straightdope.com/u/Anaglyph)\ **Post date:** [January 16, 2017, 3:16pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/15 "2017-01-16T15:16:15Z")
> [@Exapno\_Mapcase](#): > > If this is true, then why do ex-smokers have much higher risks of lung cancer than nonsmokers? > > Why are there any diseases associated with age and aging, for that matter? > > I suspect strongly that your claim isn’t true, or is in no way true the way you think it is. Particles from smoke embedded in the lung tissue are not removed by cell replacement. Daughter cells inherit the mutations that affected the parental cells ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [January 16, 2017, 3:58pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/16 "2017-01-16T15:58:31Z")
> [@Anaglyph](#): > > Particles from smoke embedded in the lung tissue are not removed by cell replacement. > Daughter cells inherit the mutations that affected the parental cells Just want to say that my question was rhetorical to show how even a moment’s thought would have revealed what a bad assumption the OP was making. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [January 16, 2017, 4:43pm UTC](https://boards.straightdope.com/t/natural-regeneration-of-body-parts-in-humans/777126/17 "2017-01-16T16:43:48Z")
As so many have said, the OP overstates the case for “lungs self-regenerate to be as good-as-new”. OTOH, there’s lots of legit info backing the idea that quitting is helpful and at least partly regenerative. So the OP’s on the right general track even if he’s off-course a bit on the specifics. From [https://www.cancer.gov/about-cancer/causes-prevention/risk/tobacco/cessation-fact-sheet#q7](https://www.cancer.gov/about-cancer/causes-prevention/risk/tobacco/cessation-fact-sheet#q7) and subsequent > [@NIH cancer website](#): > > What are the immediate benefits of quitting smoking? > > The immediate health benefits of quitting smoking are substantial: > • Heart rate and blood pressure, which are abnormally high while smoking, begin to return to normal. > • Within a few hours, the level of carbon monoxide in the blood begins to decline. (Carbon monoxide reduces the blood’s ability to carry oxygen.) > • Within a few weeks, people who quit smoking have improved circulation, produce less phlegm, and don’t cough or wheeze as often. > • Within several months of quitting, people can expect substantial improvements in lung function (21). > • Within a few years of quitting, people will have lower risks of cancer, heart disease, and other chronic diseases than if they had continued to smoke. > • In addition, people who quit smoking will have an improved sense of smell, and food will taste better > > Does quitting smoking lower the risk of cancer? > > Yes. Quitting smoking reduces the risk of developing and dying from cancer. Although it is never too late to get a benefit from quitting, the benefit is strongest among those who quit at a younger age (3). > > The risk of premature death and the chance of developing cancer from smoking depend on many factors, including the number of years a person smokes, the number of cigarettes he or she smokes per day, the age at which he or she began smoking, and whether or not he or she was already ill at the time of quitting. For people who have already developed cancer, quitting smoking reduces the risk of developing a second cancer (23-25).