Originally Posted by HardwareDecoder
I'm not sure on that either, the only things I can think of off the top of my head (no pun intended) are that brain cells don't regenerate which is why when people use inhalants and stuff that kill brain cells they literally end up being stupider every time.
Also I don't think some neurons regenerate based on my book saying they live to be 100 years older or more but I could be wrong on that.
Also as far as regenerate which is akin to healing I would imagine. Most cartilage is poorly vascularized (not much contact with blood vessels/blood) meaning it heals poorly or not at all which is why in reference to the knee when you tear your meniscus (fibrocartilage) it usually needs surgical repair in which they literally just cut out the damaged part so it doesn't effect the good tissue.
Neurons don't regenerate, for the most part. They can branch out new axons, new pathways and such. Regeneration as what you would see in another organ (not CNS/Brain) doesn't exist. They can't multiply either.
While cells regenerate, to heal, it's really minor damage. I believe Nerve cells have some of this function, they would almost have too. But this is different then when people talk about spinal regeneration or brain tissue regeneration. There were talking about the organ and it's regenerative ability. For the most part, if a cell gets seriously "injured" it's dead. What makes everything but nerve tissue unique, is it can multiply and divide! To say, you lose 50% of your liver and it'll come back just as healthy! Now, that may not happen ideally due to other factors but that is transplant amounts. (Note: That's also the best regeneration organ, sooooo yeah)
The thing is, when we suffer nerve damage like that, there is no real fix. branching out axons may not be enough, especially if there are pathways of dead cells. So you have to simulate nerve reproduction. But wait, they can't divide. So what we do, is get stem cells that will turn into nerve cells and replace what was lost. Sound familiar?
So while cell regeration is talked about, most of the time it's in the scope of the entire organ. Some organs don't require tissue to replicate that often. Your skin cells are pretty quick, while your skeleton (bone and all that jazz) is pretty slow. So there isn't a cell that regenerates every 7 years, there just isn't a cell over X years. 7 years is the mark "most" cells die off, so the average age of your cells at most will be 7 years.Edited by mushroomboy - 11/10/13 at 5:40pm