Many people fret about ageing, little realising that whatever your age in years, some of your body parts are just a few weeks, even days, old.
This is because they are constantly renewing themselves.
LIVER AGE: 5 MONTHS
The liver is known for its amazing capacity to repair and re-grow itself thanks to its rich blood supply.
This means it can continue with its main job of flushing toxins out of the body.
If you’ve ever wondered why even heavy drinkers can sometimes improve the state of their liver, it’s because liver cells only have a life span of around 150 days.
‘I can take 70 per cent of a person’s liver away in an operation and around 90 per cent of it will grow back within two months,’ explains David Lloyd, consultant liver surgeon at Leicester Royal Infirmary.
However, in heavy drinkers the parenchymal cells – the liver’s main cells – can become so damaged that scar tissue forms, a condition known as cirrhosis. So though a healthy liver can regenerate itself, with cirrhosis the damage is permanent – and sometimes fatal.
TASTE BUDS AGE: 10 DAYS
The tongue is covered with around 9,000 taste buds that help us to detect sweet, salty, bitter or sour flavours, explains Professor Damian Walmsley, scientific adviser to the British Dental Association.
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The taste buds themselves are a collection of cells on the surface of the tongue, each housing about 50 taste cells. The buds renew themselves every ten days to two weeks.
However, anything that causes inflammation, such as infections or smoking, can damage the taste buds and affect their renewal – deadening their sensitivity.
BRAIN AGE: SAME AS YOUR AGE
Most of our cells that last a lifetime are found in the brain, explains John Wadley, consultant neurosurgeon at Barts and the London Hospital.
‘We are born with all the brain cells we’ll ever have – around 100 billion – and most of the brain does not regenerate as it gets older.
In fact, we actually lose cells, which is the underlying reason for dementia and why head injuries are so devastating.
‘There are, however, two areas of the brain that do regenerate,’ says Mr Wadley. ‘The olfactory bulb that governs our sense of smell, and the hippocampus, which is an area for learning.’
HEART AGE: 20 YEARS
Until recently it was thought the heart couldn’t renew itself. However, a study at New York Medical College found it is actually dotted with stem cells that constantly rejuvenate it – at least three or four times over a lifetime, say the researchers.
LUNGS AGE: 2-3 WEEKS
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The cells in the lungs constantly renew themselves, explains Dr Keith Prowse, vice-president of the British Lung Foundation.
However, the lungs contain different cells that renew at different rates. The alveoli or air sac cells – needed for the exchange of oxygen and gases – deep in the lungs have a steady progress of regeneration that takes about a year.
Meanwhile, the cells on the lung’s surface have to renew every two or three weeks.
‘These are the lungs’ first line of defence, so have to be able to renew quickly,’ says Dr Prowse.
The lung disease emphysema can prevent this regeneration as it begins with the destruction of the alveoli, which creates permanent ‘holes’ in the walls of the lungs.
EYES AGE: SAME AS YOUR AGE
Your eyes are one of the few body parts that don’t really change during your life.
The only part that is constantly being renewed is the cornea, the transparent top layer. If this is damaged, it can recover in as little as 24 hours, says Dr Rob Hogan, president of the College of Optometrists.
‘The cornea has to have a smooth surface, so you can focus properly. That’s why the cells renew themselves so quickly.’
Unfortunately, this isn’t the case with the rest of the eye – as we age, the lens loses flexibility, which is why we struggle to focus as we get older.
October 29, 2009
