Aron Stack asked:
I had a question I was hoping you could help with.
I know that over the course of our lives we lose lots of cells that die and are replaced, but I wondered what cells are with us (if any) from birth until death? Presuming one lives to be 60 or so plus.
Chris - There are lots of cells that you do replace on a minute-by-minute basis. There are other cells that you replace, never! In other words, they do have to last a lifetime. A good example of these are some of the brain cells. Although you can produce new brain cells during life, and that was a discovery made in the last 10 or 15 years, the vast majority of the brain cells that run your brain throughout your life, you have to make last a lifetime. One of the reasons why neurodegenerative diseases like Parkinsonís and Alzheimer's disease are a problem is because once the nerve cells in certain parts of the brain die off, they're not replaced. So brain cells are a good example of a cell that lasts a lifetime.
Another one is some muscle cells. Letís take the heart as an example. Another reason why a heart attack is bad news is because when the heart is injured by a heart attack, there's an interruption of the blood flow to a territory of the heart so you will therefore lose muscle cells there, those cells in humans at least, and other high animals are not replaced. They are replaced instead by just fibrous tissue and scar tissue, so you lose physical muscle tissue, and this means the heart loses its ability to pump so well.
People used to think that fat cells were something that lasted a lifetime and that if you overfed the baby, the baby would make far too many fat cells when it was little, and this would be carried through the rest of its life and give it an increase risk of obesity. But in more recent years, there was a lady called Kirsty Spalding whoís at the Karolinska Institute in Sweden, and she actually carbon dated fat cells, and found that they last about 12 years, and so, you make new ones on a roughly 12-year basis. So you make a fat cell, it will last an average of 12 years, then you can make more fat cells.
So the answer is, your body is a mixed bag. Some cells are made and they're killed off, and replaced very, very regularly, very, very rapidly, blood cells last 120 days for example, others do have to genuinely last you a lifetime.
Most of your neurons, and many of the eye cells last a lifetime. That is one of the reasons why people have problems with the lenses of the eyes changing over time.
Aron Stack asked the Naked Scientists: Hi Chris, I had a question I was hoping you could help with. I know that over the course of our lives we lose lots of cells that die and are replaced, but I wondered what cells are with us (if any) from birth until death? Presuming one lives to be 60 or so plus. Thanks Aron What do you think? Aron Stack , Tue, 15th Mar 2011
Another one is the ova in human women- in a woman's lifetime, she creates a certain amount of egg cells, but they are never replaced. Once they're gone, they're gone. Mary Blanco, Thu, 4th Apr 2013