Cell regeneration

Received wisdom is that every cell in the body is replaced every seven years, but according to COSMOS magazine it varies by body part. 2-3 days for the lining of the small intestine, 7 days for the outer layer of the cornea (and apparently the rest of the eye doesn't regenerate at all), 180-400 days for the liver, 10 years for the brain, 15 years for muscles. The heart only regenerates about 1% of its cells each year in a young adult and less as you age.