Pigmentation refers to the concentration of colored substances, called pigments, in certain cells or tissues of the body. There are a number of different pigments. In humans, the most obvious type of pigmentation is that of the skin, the iris, which is the colored part of the eye, and the pubic and head hair. Pigment is also the cause of the color of blood, as hemoglobin gives blood its red coloring. Urine is more or less yellow depending on the amount of bilirubin, a yellow breakdown product, and fecal matter is brown because of the breakdown of the same pigment after it passes through the digestive tract. Pigmentation is dependent on genetic factors, as is eye color, as well as environmental factors, such as the skin tanning in the sun due to melanin production. Many diseases can cause alterations in certain types of pigmentation, including leprosy, kidney failure, albinism, and so on.
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Latest update on October 29, 2013 at 07:16 AM by Jeff.