Most human cells regenerate, although each cell type experiences a different life span. The notion that all human cells replace themselves after a period of seven to 10 years is a myth.
LiveScience.com reports that most brain cells, such as cerebral cortex neurons, do not replace themselves when they die. However, most cells do replace themselves on a fairly regular schedule. For example, red blood cells regenerate in roughly four months and white blood cells in about a year.
FeelGuide.com indicates that the epidermis, the skin's outer layer, regenerates about every 35 days, while the liver is capable of completely replacing itself in about six weeks. In fact the liver can regenerate in its entirety even when only as little as 25 percent of it is left. Stomach lining regenerates every four days or so, although stomach cells that make contact with digesting food regenerate in five minutes.
NYTimes.com reports that while most cell molecules are replaced periodically, human DNA is not. In other words, the same DNA is passed along during the cell regeneration process, which is why human beings continue to exhibit many of the same physical traits over the years despite regular cellular regeneration taking place many times over.