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Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
The epidermis, the outermost skin layer, looks like layers of flattened cells. The topmost layer of the epidermis, the stratum corneum, made of dead keratinocytes—skin cells which make the protein keratin—slowly flakes away as new cells replace the old from beneath. They contain a high concentration of the tough fibrous keratin. Melanocytes, another cell type in the epidermis, produce the dark skin pigment melanin which determines skin color. Skin color is genetically determined, but sunlight can stimulate the cells to produce more melanin, darkening or “tanning” the skin. The more melanin the darker the skin. However, melanocytes can also transform to become the dangerous skin cancer, malignant melanoma.
Fractal Dimension of Skin Lesions
Published in Dinesh K. Kumar, Sridhar P. Arjunan, Behzad Aliahmad, Fractals, 2017
Dinesh K. Kumar, Sridhar P. Arjunan, Behzad Aliahmad
Melanin also acts as natural sunscreen. It protects the skin’s underlying tissues and organs from the damaging effect of ultra violet (UV) radiation of the sun’s rays. The photochemical properties of melanocytes allows for production of melanin in response to UV light exposure and prevents subsequent DNA damage and associated life threatening problems such as melanoma (a type of skin cancer). Due to having greater amount of pigmentation and higher melanin content, individuals with darker skin color are at lower risk of developing melanoma than light complexioned people. Therefore tanning, the condition where the skin darkens by production of more amount of melanin, is the natural and protective response of lighter complexion skins to sun exposure and UV light stimulation.
Tissue Biomechanics
Published in Ronald L. Huston, Principles of Biomechanics, 2008
Skin is sometimes referred to as the largest organ of the body. Mechanically, it is a membrane serving as a covering for the body. Skin consists of three main layers. The outer layer called the epidermis is the visible palpable part. The epidermis covers a middle layer, called the dermis, which in turn rests upon a subcutaneous (subskin) layer of fatty tissue as represented in Figure 7.7. The skin color is due to melanin contained in the epidermis.
Effects of anti-wrinkle and skin-whitening fermented black ginseng on human subjects and underlying mechanism of action
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Jin Ju Park, Junmin An, Jung Dae Lee, Hyang Yeon Kim, Jueng Eun Im, Eunyoung Lee, Jaehyoun Ha, Chang Hui Cho, Dong-Wan Seo, Kyu-Bong Kim
The skin is a protective outer covering extending throughout the human body which protects internal tissues and organs. Human skin is composed of three primary layers; the epidermis, dermis, and hypodermis. The epidermis, the outermost layer of the skin, functions by protecting the body and is predominantly composed of keratinocytes, melanocytes, Langerhans, and Merkel cells. Keratinocytes are the most abundant cells found in the epidermis and function as a barrier against the external environment (McGrath, Eady, and Pope 2004; Winkelmann and Breathnach 1973). Melanocytes produce the colored pigment of melanin. Melanin occurs in two forms in human skin: eumelanin and pheomelanin. Eumelanin is black and brown melanin and common throughout the body, while pheomelanin is a red or yellow melanin pigment (Wakamatsu and Ito 2002). Melanin is biosynthesized from tyrosine. Tyrosine is converted to DOPA (3,4-dihydroxy-L-phenylalanine), which is then oxidized to DOPA-quinone and subsequently converted to DOPA-chrome. Melanin is finally generated through several intermediates and a series of biochemical steps. Tyrosinase plays a key role in the melanin biosynthetic pathway by converting tyrosine to DOPA (Choi et al. 2001; D’Mello et al. 2016; Kong et al. 2000). The inhibition of tyrosinase leads to blockade of melanin production. The reaction of tyrosinase (activity or inhibition) with test material is used as a measure of efficacy of the compound. Melanin, which is synthesized and matures in the melanosome, is transferred to keratinocytes where pigmentation occurs. Skin color is determined by melanin in the melanocytes. Melanocytes function predominantly by producing melanin pigment, which protects against and absorbs harmful ultraviolet (UV) radiation (D’Mello et al. 2016).
Effects of anti-wrinkle and skin-whitening fermented black ginseng on human subjects and underlying mechanism of action
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Jin Ju Park, Junmin An, Jung Dae Lee, Hyang Yeon Kim, Jueng Eun Im, Eunyoung Lee, Jaehyoun Ha, Chang Hui Cho, Dong-Wan Seo, Kyu-Bong Kim
The skin is a protective outer covering extending throughout the human body which protects internal tissues and organs. Human skin is composed of three primary layers; the epidermis, dermis, and hypodermis. The epidermis, the outermost layer of the skin, functions by protecting the body and is predominantly composed of keratinocytes, melanocytes, Langerhans, and Merkel cells. Keratinocytes are the most abundant cells found in the epidermis and function as a barrier against the external environment (McGrath, Eady, and Pope 2004; Winkelmann and Breathnach 1973). Melanocytes produce the colored pigment of melanin. Melanin occurs in two forms in human skin: eumelanin and pheomelanin. Eumelanin is black and brown melanin and common throughout the body, while pheomelanin is a red or yellow melanin pigment (Wakamatsu and Ito 2002). Melanin is biosynthesized from tyrosine. Tyrosine is converted to DOPA (3,4-dihydroxy-L-phenylalanine), which is then oxidized to DOPA-quinone and subsequently converted to DOPA-chrome. Melanin is finally generated through several intermediates and a series of biochemical steps. Tyrosinase plays a key role in the melanin biosynthetic pathway by converting tyrosine to DOPA (Choi et al. 2001; D’Mello et al. 2016; Kong et al. 2000). The inhibition of tyrosinase leads to blockade of melanin production. The reaction of tyrosinase (activity or inhibition) with test material is used as a measure of the efficacy of the compound. Melanin, which is synthesized and matures in the melanosome, is transferred to keratinocytes where pigmentation occurs. Skin color is determined by melanin in the melanocytes. Melanocytes function predominantly by producing melanin pigment, which protects against and absorbs harmful ultraviolet (UV) radiation (D’Mello et al. 2016).