If the cells in our body are replaced every 7 to 10 years, why cant it roll itself back into a position where it worked better than it does now?

Question

For example: Someone has a disease, why cant the body just reset itself to how it was before it had the disease to get rid of the negative effects?

In: Biology

Answer 1

It’s a false assumption that our body is replaced new cells every 7 to 10 years. Cells in your body can be divided into 3 types generally based on how they divide:

1. Always dividing: These are generally found in places that generally face a lot of wear and tear, like the skin, or the mucosa lining the inside of your mouth, stomach and intestines. Since they divide very fast, they can heal most wounds to them. That’s why cuts or scratches heal so fast.

2. Not dividing right now, but can divide if and when necessary: Like your liver, or the lymphocytes (type of a white blood cell). That’s why you can donate part of your liver and it grows right back.

3. Cannot divide at all: Examples are your neurons (the cells that make your brain and nerves), your heart muscle cells and the fat cells. That’s why heart attacks and head injuries have a poor prognosis.

Also, even dividing cells divide at very different rates. Skin regenerates very fast while some stem cells are pretty slow. So when they say the body replaces itself in 7 to 10 years, what they actually means that the dividing cells in your body have created enough cells to weigh as much as you. In reality what happens is, you shed off an immense quantity of cells that are damaged and cannot work.

So, when disease occurs in the parts of body which cannot divide and repair itself, or the disease occurs at a speed higher than the rate of regeneration of cells, you get ill.