Your hearts stops, your blood goes cold and your limbs stiffen. Yet amidst the signs that you are no more, your fingernails continue to lengthen and your hair grows – or so we’re told.
Not surprisingly there haven’t been many systematic studies measuring daily changes in fingernail and hair length in the dead. For hints we can turn to historical anecdotes and descriptions provided by medical students working with cadavers. Transplant surgeons are also experienced in calculating the length of time the different kinds of cells continue to function beyond death. Different cells die at different rates. After the heart stops beating, oxygen supply to the brain is cut off. With no glucose store to rely on, nerve cells die within three to seven minutes.
Transplant surgeons must remove kidneys, livers and hearts from donors within thirty minutes of death and get them into recipients inside six hours. Skin cells, meanwhile, are longer lived. Grafts can still be successful if taken 12 hours after death.
In order for fingernails to grow, new cells need to be produced and this can’t happen without glucose. Fingernails grow by an average of 0.1mm per day, a rate which slows as we age. A layer of tissue beneath the base of the nail called the germinal matrix is responsible for producing the vast majority of the cells which form the newest-growing part of the fingernail. The new cells push the older ones forwards, making the nail appear to lengthen from the tip. Death puts a stop to the supply of glucose, and therefore to fingernail growth. Via Do your hair and fingernails grow after death?.