How old are you?  It’s a tougher question to answer than you think.  There are about 37 trillion cells in the body and each type of cell has it’s own lifespan. The average age of an adult’s cells may be as low as 7 – 15 years.  This is because most of the body’s tissues are undergoing constant renewal.

For example: cells that line the stomach last about five days because they are exposed to stomach acid and our red blood cells last about 120 days. The surface of our skin is renewed every two weeks.  Skin cells are recylced so often because it is easily damaged by wear and tear.  Liver cells, which battle toxins, poisons, drugs and alcohol last about 300 – 500 days.

Other tissues last years – the human skeleton is completed replaced about every 10 years or so.

A few parts of the body last our entire lifetime, including the neurons of the cerebral cortex, the inner lens cells of the eye and some heart tissue. Additionally,  females do not regenerate oocytes; all the eggs they will ever have are present at birth.