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Thread: Determinants of skin color

  1. #1

    Default Determinants of skin color

    Normal skin color result from a combination of hemoglobin, melanin, and carotene.

    1.Hemoglobin is an oxygen-binding protein present within red blood cells. Upon binding oxygen, hemoglobin exhibits a bright red color, giving blood vessels in the dermis a bright reddish tint that is most easily seen in the skin of lightly pigmented individuals.

    2.Melanin is a pigment produced and stored in melanocytes. This pigment is synthesized from the amino acid tyrosine, and its production requires the enzyme tyrosinase. There are two types of melanin, eumelanin and pheomelanin, and they occur in various ratios of yellow, reddish, tan, brown, and black shades. Melanin is transferred in membrane-bound vesicles from melanocytes to keratinocytes in the stratum basale and stratum spinosum via phagocytosis or exocytosis. The keratinocytes that receive the melanin are displaced toward the stratum corneum, and thus melanocyte activity affects the color of the entire epidermis.

    All people have about the same number of melanocytes. However, melanocyte activity and the color of the melanin produced by these cells varies among individuals and races, resulting in different skin tones.

    Darker-skin individuals have melanocytes that produce relatively more melanin than do those of lighter-skinned individuals. Further, these more active melanocytes tend to package and send melanin to cells in the more superficial epidermal layers, such as the stratum granulosum.

    The amount of melanin in the skin is determined by both heredity and light exposure. Melanin pigment surrounds the keratinocyte nucleus, where it absorbs ultraviolet (UV) radiation in sunlight, thus preventing damage to nuclear DNA. Exposure to UV light both darkens melanin already present and stimulates melanocytes to make more melanin.

    Carotene is a yellow-orange pigment that is acquired in the body by eating various yellow-orange vegetables. Normally, carotene accumulates inside keratinocytes of the stratum corneum and within the subcutaneous fat. In the body, carotene is converted into vitamin A, which has an important function in normal vision. Additionally, carotene has been implicated in reducing the number of potentially dangerous molecules formed during normal metabolic activity and in improving immune cell number and activity.
    Last edited by Janis.Y.Chen; Mon 9th May '16 at 5:23pm.
    Clinical Pharmacy Specialist - Infectious Diseases

  2. #2

    Default Dermatologyphics


    The study of friction ridge patterns is known as dermatoglyphics. Friction ridge patterns are well formed by the fourth month of fetal development, and are unique identifier because no two individuals share the same set of fingerprints. Even identical twins have different fingerprints.

    Biological anthropologists and other scientists have studied dermatoglyphics among different populations. They have found gender differences in dermatoglyphic patterns. For example, males tend to have relatively more whorls in their fingerprint patterns, whereas females tend to have relatively more arches. Some regional populations also exhibit characteristic dermatoglyphic patterns.
    Last edited by Janis.Y.Chen; Mon 9th May '16 at 9:00pm.
    Clinical Pharmacy Specialist - Infectious Diseases

  3. #3

    Default Re: Determinants of skin color

    Stretch Marks, Wrinkles, and Lines of Cleavage

    The majority of the collagen and elastic fibers in the skin are oriented in parallel bundles at specific body locations. The alignment of fiber bundles within the dermis is a result of the direction of applied stress during routine movement; therefore, the function of the bundles is to resist stress. Lines of cleavage in the skin identify the predominant orientation of collagen fiber bundles. These are clinical and surgically significant because any procedure resulting in a cut at right angles to a cleavage line usually is pulled open as a result of the recoil resulting from cut elastic fibers. This often results in slow healing and increased scarring. In contrast, an incision made parallel to a cleavage line usually will remain closed. Therefore, surgical procedures should be planned to consider lines of cleavage, thus ensuring rapid healing and prevention of scarring.

    Determinants of skin color-screen-shot-2016-05-09-at-8-15-15-pm-jpg

    Collagen fibers and elastic fibers together contribute to the physical characteristics of the skin. Whereas the collagen fibers impart tensile strength, elastic fibers allow some stretch and recoil in the dermis during normal movement activities. Stretching of the skin that may occur as a result of excessive weight gain or pregnancy often exceeds the elastic capabilities of the skin. When the skin is stretched beyond its capacity, some collagen fibers are torn and result in stretch marks, called striae (str ́;stria=furrow). Both the flexibility and thickness of the dermis are diminished by effects of exposure to ultraviolet light and aging, causing either sagging or wrinkled skin.
    Last edited by Janis.Y.Chen; Mon 9th May '16 at 9:58pm.
    Clinical Pharmacy Specialist - Infectious Diseases

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