Myth:
You may have read on online journals or a smart mouth friend to claim that human body replaces itself at the cellular level every seven years. It is amazing to hear that you will be starting afresh after a few years. But it is not true. Many cells do replace them over time but the brand new body concept is just an internet myth. Let us do a quick anatomy review of our body’s most basic building material. We have got two hundred different types of cells which specialize for different purposes. Groups of similar cells come together to form different kinds of tissues which combine to form organs. All these cells work together to keep you alive but some duties are harder on individual cells than others. Cells are dying and being replaced all the time but how quickly can vary a lot depending on where they are in your body and what they do.
Replaceable:
Take the cells that line in your stomach and intestines. Their job is not easy getting constantly battered by chicken wings and doused in stomach acid, they typically only lasts for a couple of days before they end up in the toilet. Your skin cells have a pretty rough time too acting as your first veteran of defense against pathogens. So they are pretty much constantly shed but are fully replaced every few weeks. Red blood cells are incapable of healing themselves because they don’t have DNA so they last about four months or so before all the oxygen carrying constant circulation in the bloodstream finally wears them out. Some white blood cells can only live for a couple of months while others like your neutrophils are some of the first responders to fight infection and only last hours.
Bone Cells:
Your bone cells are constantly being replaced but your skeleton which is not made of cells but only built by cells takes about 10 years to get a full remodel. Other cells stick around for a while like most of your muscle cells. In fact your cardiomyocytes or heart muscle cells replace incredibly slowly like 1% per year after you are 20 and even more slowly when you get older. By the end of a long life you will probably still have more than half of the cells you had when you were born.
Irreplaceable:
Then there are other cells that are never replaced. What you initially grow is all you will ever get. For example, biosex females are born with all the OOCYTES or egg cells that they will ever have. Male or female you can not make more tooth enamel either. Certain neurons like those in your cortex irreplaceable which is one of the reasons we can not reverse diseases like Alzheimer’s and Parkinson’s.
Measurement:
So how do we even know all of this? Nuclear weapon detonation during the Cold War released a whole bunch of radioactive material into the atmosphere in the form of carbon called carbon 14. This carbon 14 combines with oxygen and form carbon dioxide. It’s taken up to your cells and DNA. And since a cell doesn’t replace its DNA in a lifetime, its carbon 14 levels remain the same from creation to death. So by measuring the level of carbon 14 we can know the age of a certain cell.
Transcripted By Benazir Elahee Munni