Melanin is a pigment that determines the color of hair and skin.

Melanocytes are cell found in the stratum basale of the epidermis that produces the pigment melanin.

 

Humans who left Africa and settled in Europe about 40,000 years most likely had dark skin with high levels of melanin, which provides protection against ultraviolet radiation New data confirms that about 8,500 years ago, early hunter-gatherers in Spain, Luxembourg, and Hungary also had darker skin. Skin pigmentation is an adaptation to ultraviolet radiation, with different tones offering different advantages, depending on one’s distance from the equator. As humans migrated to the Northern Hemisphere, they were exposed to less ultraviolet radiation, which also meant less absorption of the Vitamin D needed for strong bones and other important immune functions. In order to compensate for this loss and to allow for greater exposure to ultraviolet radiation, skin pigmentation became lighter.

The basal layer is the innermost layer of the epidermis, and contains small round cells called basal cells. The basal cells continually divide, and new cells constantly push older ones up toward the surface of the skin, where they are eventually shed. The basal cell layer is also known as the stratum germinativum due to the fact that it is constantly germinating (producing) new cells.

The basal cell layer contains cells called melanocytes. Melanocytes produce the skin coloring or pigment known as melanin, which gives skin its tan or brown color and helps protect the deeper layers of the skin from the harmful effects of the sun. Sun exposure causes melanocytes to increase production of melanin in order to protect the skin from damaging ultraviolet rays, producing a suntan. Patches of melanin in the skin cause birthmarks, freckles and age spots. Melanoma develops when melanocytes undergo malignant transformation.

Merkel cells, which are tactile cells of neuroectodermal origin, are also located in the basal layer of the epidermis.

The first thing a clinician sees is the skin, and so the examination of the skin should be part of any thorough physical examination. Most skin disorders are relatively benign, but a few, including melanomas, can be fatal if untreated. A couple of the more noticeable disorders, albinism and vitiligo, affect the appearance of the skin and its accessory organs. Although neither is fatal, it would be hard to claim that they are benign, at least to the individuals so afflicted.

Albinism is a genetic disorder that affects (completely or partially) the coloring of skin, hair, and eyes. The defect is primarily due to the inability of melanocytes to produce melanin. Individuals with albinism tend to appear white or very pale due to the lack of melanin in their skin and hair. Recall that melanin helps protect the skin from the harmful effects of UV radiation. Individuals with albinism tend to need more protection from UV radiation, as they are more prone to sunburns and skin cancer. They also tend to be more sensitive to light and have vision problems due to the lack of pigmentation on the retinal wall. Treatment of this disorder usually involves addressing the symptoms, such as limiting UV light exposure to the skin and eyes. In vitiligo, the melanocytes in certain areas lose their ability to produce melanin, possibly due to an autoimmune reaction. This leads to a loss of color in patches (image). Neither albinism nor vitiligo directly affects the lifespan of an individual.

Other changes in the appearance of skin coloration can be indicative of diseases associated with other body systems. Liver disease or liver cancer can cause the accumulation of bile and the yellow pigment bilirubin, leading to the skin appearing yellow or jaundiced (jaune is the French word for “yellow”). Tumors of the pituitary gland can result in the secretion of large amounts of melanocyte-stimulating hormone (MSH), which results in a darkening of the skin. Similarly, Addison’s disease can stimulate the release of excess amounts of adrenocorticotropic hormone (ACTH), which can give the skin a deep bronze color. A sudden drop in oxygenation can affect skin color, causing the skin to initially turn ashen (white). With a prolonged reduction in oxygen levels, dark red deoxyhemoglobin becomes dominant in the blood, making the skin appear blue, a condition referred to as cyanosis (kyanos is the Greek word for “blue”). This happens when the oxygen supply is restricted, as when someone is experiencing difficulty in breathing because of asthma or a heart attack. However, in these cases the effect on skin color has nothing do with the skin’s pigmentation.

Vitiligo is not the only disease that causes skin to change color.

Here are a few conditions and what they look like, including vitiligo.

Talk to your health care provider if you think you might have vitiligo or another skin condition.