787 pages on this wiki. Mark Andrew Spitz (born February 10, 1950) is a retired American swimmer. He won seven gold medals at the 1972 Summer Olympics, an achievement only surpassed by Michael Phelps who won eight golds at the 2008 Olympics.Spitz set new world records in all seven events in which he competed, a record that still stands.87 pages on this wiki. Mark Andrew Spitz (born February 10, 1950) is a retired American swimmer. He won seven gold medals at the 1972 Summer Olympics, an achievement only surpassed by Michael Phelps who won eight golds at the 2008 Olympics.
The colour of the skin is determined by the concentrations of three main pigments: melanin, carotene and haemoglobin. These are found in the dermis and combine to produce the pigmentation of all surface tissues including the skin, mucous membranes, and even the eyes.
Scientists have uncovered how human skin cells control pigmentation â a discovery that could lead to safer ways to tan or lighten the skin. Researchers found that skin color can be regulated by estrogen and progesterone, two of the main female sex hormones. Estrogen darkens the skin; progesterone lightens the skin. Although this much was known to a limited degree, the new research revealed two cellular receptors that appear to control this process in skin cells called melanocytes.