To be honest- I have no idea:)
But thinking about it- it old be quite a challange to count every cell in our body at every stage of life- and that depends on the person too (think about some body- builders- they must have more muscle cells!).
I think the number of cells in an adult is relatively similar through most of our life- we do lose some neurons perhaps. I know it’s not a great answer, hope someone else can help you with it soon ðŸ™‚

Karolina is right – it’s a challenge to count exactly how many cells are in our body at any one time, so no body knows for sure just how much our cell number may reduce or increase with age. Another reason is that scientists are still trying to work out exactly what is going on when we age. I will tell you what we know so far…

On the whole, our body is very good at keeping the same number of cells once we are fully grown. Our cells can divide to make new cells if we need them, and can be killed if we need to get rid of them (if they are dangerous for example).

What we do know is that as we get older, some of our cells lose their ability to keep dividing to make new cells (we call this cellular senescence). This could mean two things. 1) We end up with the same number of cells because we can’t make any more. Or, 2) because we need to replace many of the cells in our body (we lose millions of skin cells each day!) and if our cells can’t divide any more, then the number of cells in our body would decrease.

Throughout our life, some of our cells are deliberately killed by a process called apoptosis. This would cause cell number to reduce, but our body makes sure it balances the number of cells it kills off with the number of new ones it makes, so on the whole cell numbers stay pretty constant. But as we get older, apoptosis can also go wrong. It might stop killing cells it should be killing off (so we get more), or it might kills cells that it shouldn’t be killing (so we get fewer cells).

As well as apoptosis going wrong as we get older, there is a greater chance of our cells dividing out of control. This is what happens in cancer. Because the cells are dividing out of control and are avoiding being killed off, then their numbers increase.

So, on one hand you might say cell number reduces as we get older. On the other hand you could say they increase…

On average we have about 40 trillion cells in our body! That is a MASSIVE number. Losing or gaining a few cells wouldn’t change this number much in the grand scheme of things. But if cells are lost in certain places, then this can be a very big problem indeed (think what would happen if you lost cells in your brain, or your heart for example).

Sorry that was a bit of a longer answer!

Ps. Body builders do not get bigger muscles through having more muscle cells.

Hayley has dealt with this really well but also remember that some cells are more critical than others and can’t be readily replaced. So with ageing, we see increased problems with eg Alzheimer’s disease, where brain cells die, and similarly loss of retinal epithelial cells causes age-related macular degeneration, as shown in lecture 3. Cell senescence leads to the inability to replace cells lining blood vessels, problems with wound healing and particularly issues with mounting effective immune responses as this needs massive cell proliferation. So losing some cell types can cause serious diseases in older people; it’s not so much the total number of cells that matters but what the cells do.

## Comments

Hayleycommented on :Hi there ðŸ™‚

Karolina is right – it’s a challenge to count exactly how many cells are in our body at any one time, so no body knows for sure just how much our cell number may reduce or increase with age. Another reason is that scientists are still trying to work out exactly what is going on when we age. I will tell you what we know so far…

On the whole, our body is very good at keeping the same number of cells once we are fully grown. Our cells can divide to make new cells if we need them, and can be killed if we need to get rid of them (if they are dangerous for example).

What we do know is that as we get older, some of our cells lose their ability to keep dividing to make new cells (we call this cellular senescence). This could mean two things. 1) We end up with the same number of cells because we can’t make any more. Or, 2) because we need to replace many of the cells in our body (we lose millions of skin cells each day!) and if our cells can’t divide any more, then the number of cells in our body would decrease.

Throughout our life, some of our cells are deliberately killed by a process called apoptosis. This would cause cell number to reduce, but our body makes sure it balances the number of cells it kills off with the number of new ones it makes, so on the whole cell numbers stay pretty constant. But as we get older, apoptosis can also go wrong. It might stop killing cells it should be killing off (so we get more), or it might kills cells that it shouldn’t be killing (so we get fewer cells).

As well as apoptosis going wrong as we get older, there is a greater chance of our cells dividing out of control. This is what happens in cancer. Because the cells are dividing out of control and are avoiding being killed off, then their numbers increase.

So, on one hand you might say cell number reduces as we get older. On the other hand you could say they increase…

On average we have about 40 trillion cells in our body! That is a MASSIVE number. Losing or gaining a few cells wouldn’t change this number much in the grand scheme of things. But if cells are lost in certain places, then this can be a very big problem indeed (think what would happen if you lost cells in your brain, or your heart for example).

Sorry that was a bit of a longer answer!

Ps. Body builders do not get bigger muscles through having more muscle cells.

Lynnecommented on :Hayley has dealt with this really well but also remember that some cells are more critical than others and can’t be readily replaced. So with ageing, we see increased problems with eg Alzheimer’s disease, where brain cells die, and similarly loss of retinal epithelial cells causes age-related macular degeneration, as shown in lecture 3. Cell senescence leads to the inability to replace cells lining blood vessels, problems with wound healing and particularly issues with mounting effective immune responses as this needs massive cell proliferation. So losing some cell types can cause serious diseases in older people; it’s not so much the total number of cells that matters but what the cells do.