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The skin weighs an average of four kilograms, covers an area of two square metres, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. [1] The two main types of human skin are: glabrous skin, the hairless skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin. [3]
Hyperpigmentation can be diffuse or focal, affecting such areas as the face and the back of the hands. Melanin is produced by melanocytes at the lower layer of the epidermis. Melanin is a class of pigment responsible for producing color in the body in places such as the eyes, skin, and hair. The process of melanin synthesis (melanogenesis ...
Heterochromia iridum. Heterochromia is a variation in coloration most often used to describe color differences of the iris, but can also be applied to color variation of hair [ 1] or skin. Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment ). It may be inherited, or caused by genetic mosaicism ...
Fitzpatrick scale. The Fitzpatrick scale (also Fitzpatrick skin typing test; or Fitzpatrick phototyping scale) is a numerical classification schema for human skin color. It was developed in 1975 by American dermatologist Thomas B. Fitzpatrick as a way to estimate the response of different types of skin to ultraviolet (UV) light. [ 2]
Keratosis pilaris. Keratosis pilaris ( KP; also follicular keratosis, lichen pilaris, or colloquially chicken skin[ 1]) is a common, autosomal - dominant, genetic condition of the skin's hair follicles characterized by the appearance of possibly itchy, small, gooseflesh -like bumps, with varying degrees of reddening or inflammation. [ 2]
The genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades. [14] [15] Differences in skin color are also attributed to differences in size and distribution of melanosomes in the skin. [9] Melanocytes produce two types of melanin.
Uncombable hair syndrome ( UHS) is a rare structural anomaly of the hair with a variable degree of effect. It is characterized by hair that is silvery, dry, frizzy, wiry, and impossible to comb. [ 4] It was first reported in the early 20th century. [ 5] It typically becomes apparent between the ages of 3 months and 12 years. [ 6]
[11] [12] Acute exposure may lead to a painful sunburn, which can increase the chances of developing serious skin problems later in life. [13] Long-term sunlight exposure is known to be associated with the development of some types of skin cancer, skin aging, immune suppression, eye diseases such as cataracts. [14] [15]