23 July 2012

Do our hair and nails really grow after we are dead?

Many people will tell you that once you have died your hair and nails will continue to grow for days afterwards, with the exact time period varying depending on the individual telling the story. This popular piece of 'common fact' is undeniably interesting, but sadly, is completely incorrect; being nothing more than a frequently repeated tale of urban mythology. To put it simply, when you are dead your metabolism has completely ceased and among many things, this means that your body cannot create any new material like hair and nail tissue.

This is an electron micrograph of a human hair follicle. Hair is formed from rapidly dividing skin cells that are killed almost as soon as they are formed and filled in with a insoluble biological 'wax' and colouring pigments. They are then wrapped up a bundle of keratin fibres to form a helical strand of hair. The strand then grows from its bottom as new cells push the older ones upwards. Nails grow in much the same way, except they are laid down in sheets rather than as a helix.

Yet despite this, a deceased person's hair and nails do appear to grow for nearly a week after they have died... Although this may appear confusing at first glance, the answer to the conundrum is in fact very mundane: the human body is predominantly composed of water and over time, a cadaver dehydrates. As the cadaver looses water into the surrounding environment, their skin contracts and exposes already grown (but previously hidden) hair and nail tissue. It is surprising how much of these materials your body has tucked away beneath your skin and, by contracting, gives the impression that they are eerily growing post-death on their own accord...

Dehydrating skin also explains another common feature of corpses, whereupon they appear to smile. As the skin around their mouth becomes tighter it contracts and pulls the lips away the mouth, giving the impression of a somewhat grotesque smile.

Thus the simple action of water moving out of our bodies after our death has instigated confusion for hundreds of years, giving rise to a popular story that many people incorrectly believe as fact!

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