The Amazing Truth of Our 'Young' Bodies

As we get older and our bones start to creak, it's easy to forget just how amazing the body's capacity to repair itself actually is.

We may feel like we're getting older, but many of our most important body parts are constantly regenerating themselves -- some regularly, others over a period of years.

And what that means is certain parts of our body are a good deal younger than we are.

Studies into cell renewal are still ongoing and more is being learned all the time, but here's what we know so far:

Hair
Hair grows at a rate of about half an inch per month, and goes through three distinct stages, which can last a total of six years in women and three years in men.

Most of this time is taken up by growth, and at any one time 90 percent of the hair on our head are growing. Over the final six months the hair starts to loosen, and then finally it is pushed out by a new follicle.

In this way, your hair is never more than six years old at most.

Heart
The heart is one area in which studies into cell regeneration have produced new findings. It used to be assumed that the heart wasn't capable of regenerating itself, but now it's known that heart tissue is indeed replaced.

How long this takes is still the subject of study, but it's known to be less than 20 years. Added to that, the heart can repair some of the damage caused by a heart attack.

Lungs
We all put our lungs under a great deal of strain, even if we're not smoking. Breathing in the pollutants from everyday life leads to cells on the outermost levels of our lungs replacing themselves every few days.

Deeper tissue, meanwhile, remains in place for longer, but is still regenerated over the course of a year, although that doesn't mean we can't do ourselves permanent damage with things such as cigarettes.

Stomach
The stomach acid which helps us digest food is strong stuff, meaning that our stomachs also need to be strong to cope with it. For this reason, our stomachs are lined with mucus which replaces itself at least every five days.

But smoking can slow this and lead to stomach ulcers as the lack of mucus will allow acid to attack the stomach wall.