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Freckles
Freckles are clusters of concentrated melaninized cells which are most easily visible on people with a fair complexion. Freckles do not have an increased number of the melanin-producing cells, or melanocytes, but instead have melanocytes that overproduce melanin granules ( melanosomes) changing the coloration of the outer skin cells (keratinocytes). As such, freckles are different from lentigines and moles, which are caused by accumulation of melanocytes in a small area. Freckles can appear on all types of skin tones. Of the six Fitzpatrick skin types, they are most common on skin tones 1 and 2, which usually belong to North Europeans. However, it can also be found on people all over the world. In England a historical term for freckles is summer-voys, sometimes spelt summervoise, which may be related to the German term ''Sommersprossen''. Biology The formation of freckles is caused by exposure to sunlight. The exposure to UV-B radiation activates melanocytes to increase mela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lentigo
A lentigo () (plural lentigines, ) is a small pigmented spot on the skin with a clearly defined edge, surrounded by normal-appearing skin. It is a harmless (benign) hyperplasia of melanocytes which is linear in its spread. This means the hyperplasia of melanocytes is restricted to the cell layer directly above the basement membrane of the epidermis where melanocytes normally reside. This is in contrast to the "nests" of multi-layer melanocytes found in moles (melanocytic nevi). Because of this characteristic feature, the adjective "lentiginous" is used to describe other skin lesions that similarly proliferate linearly within the basal cell layer.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. p. 1101. .''Robbins and Cotran Pathologic Basis of Disease'' Elsevier. 2005. p. 1232. . Diagnosis Conditions characterized by lentigines include: * Lentigo simplex * Solar lentigo (Liver spots) * PUVA lentigines * Ink spot lentigo * LEOPARD syndrome * Muc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melanin
Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are five basic types of melanin: eumelanin, pheomelanin, neuromelanin, allomelanin and pyomelanin. Melanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino acid tyrosine is followed by polymerization. Pheomelanin is a cysteinated form containing poly benzothiazine portions that are largely responsible for the red or yellow tint given to some skin or hair colors. Neuromelanin is found in the brain. Research has been undertaken to investigate its efficacy in treating neurodegenerative disorders such as Parkinson's. Allomelanin and pyomelanin are two types of nitrogen-free melanin. The phenotypic color variation observed in the epidermis and hair of mammals is primarily determi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MC1R
The melanocortin 1 receptor (MC1R), also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein–coupled receptor that binds to a class of pituitary peptide hormones known as the melanocortins, which include adrenocorticotropic hormone (ACTH) and the different forms of melanocyte-stimulating hormone (MSH). It is coupled to Gαs and upregulates levels of cAMP by activating adenylyl cyclase in cells expressing this receptor. It is normally expressed in skin and melanocytes, and to a lesser degree in periaqueductal gray matter, astrocytes and leukocytes. In skin cancer, MC1R is highly expressed in melanomas but not carcinomas. MC1R is one of the key proteins involved in regulating mammalian skin color and hair color. It is located on the plasma membrane of specialized cells known as melanocytes, which produce the pigment melanin through the process of melanogenesis. It controls the typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultraviolet Light And Cancer
Exposure of skin to ultraviolet radiation from sunlight presents both positive and negative health effects. On the positive side, UV exposure enables the synthesis of vitamin D3, which is essential for bone health and potentially plays a role in inhibiting certain cancers. While vitamin D can also be obtained through dietary supplements, UV exposure offers benefits such as enhanced subdermal nitric oxide production and improved endorphin levels, which are not achievable through supplementation alone. Additionally, exposure to visible light supports melatonin synthesis, maintains circadian rhythms, and reduces the risk of seasonal affective disorder. However, UV radiation is also a mutagen and carcinogen for the skin, posing significant risks. Acute exposure can lead to painful sunburns and increase the likelihood of developing serious skin conditions later in life. Prolonged exposure is associated with the development of skin cancers, photoaging or premature skin aging, imm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea in the south. The Japanese archipelago consists of four major islands—Hokkaido, Honshu, Shikoku, and Kyushu—and List of islands of Japan, thousands of smaller islands, covering . Japan has a population of over 123 million as of 2025, making it the List of countries and dependencies by population, eleventh-most populous country. The capital of Japan and List of cities in Japan, its largest city is Tokyo; the Greater Tokyo Area is the List of largest cities, largest metropolitan area in the world, with more than 37 million inhabitants as of 2024. Japan is divided into 47 Prefectures of Japan, administrative prefectures and List of regions of Japan, eight traditional regions. About three-quarters of Geography of Japan, the countr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White People
White is a Race (human categorization), racial classification of people generally used for those of predominantly Ethnic groups in Europe, European ancestry. It is also a Human skin color, skin color specifier, although the definition can vary depending on context, nationality, ethnicity and point of view. Description of populations as "White" in reference to their skin color is occasionally found in Greco-Roman ethnography and other ancient or medieval sources, but these societies did not have any notion of a White race or pan-European identity. The term "White race" or "White people", defined by their light skin among other physical characteristics, entered the major European languages in the later seventeenth century, when the concept of a "unified White" achieved greater acceptance in Europe, in the context of racialization, racialized slavery and social status in the European colonies. Scholarship on Race (human categorization), race distinguishes the modern concept from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asia
Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilisations. Its 4.7 billion people constitute roughly 60% of the world's population. Asia shares the landmass of Eurasia with Europe, and of Afro-Eurasia with both Europe and Africa. In general terms, it is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, and on the north by the Arctic Ocean. The border of Asia with Europe is a social constructionism, historical and cultural construct, as there is no clear physical and geographical separation between them. A commonly accepted division places Asia to the east of the Suez Canal separating it from Africa; and to the east of the Turkish straits, the Ural Mountains an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Skin
Dark skin is a type of human skin color that is rich in melanin pigments. People with dark skin are often referred to as black people, although this usage can be ambiguous in some countries where it is also used to specifically refer to different ethnic groups or populations. The evolution of dark skin is believed to have begun around 1.2 million years ago, in light-skinned early hominid species after they moved from the equatorial rainforest to the sunny savannas. In the heat of the savannas, better cooling mechanisms were required, which were achieved through the loss of body hair and development of more efficient perspiration. The loss of body hair led to the development of dark skin pigmentation, which acted as a mechanism of natural selection against folate (vitamin B9) depletion, and to a lesser extent, Direct DNA damage, DNA damage. The primary factor contributing to the evolution of dark skin pigmentation was the breakdown of folate in reaction to ultraviolet radiat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dermatology
Dermatology is the branch of medicine dealing with the Human skin, skin.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. Page 537. . It is a speciality with both medical and surgical aspects. A List of dermatologists, dermatologist is a specialist medical doctor who manages diseases related to skin. Etymology Attested in English in 1819, the word "dermatology" derives from the Ancient Greek, Greek δέρματος (''dermatos''), genitive of δέρμα (''derma''), "skin" (itself from δέρω ''dero'', "to flay") and -λογία ''wikt:-logia, -logia''. Neo-Latin ''dermatologia'' was coined in 1630, an anatomical term with various French and German uses attested from the 1730s. History In 1708, the first great school of dermatology became a reality at the famous Hôpital Saint-Louis in Paris, and the first textbooks (Willan's, 1798–1808) and atlases (Jean-Louis-Marc Alibert, Alibert's, 1806–1816) appeared in print around the same time.Freedber ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UV Light
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs, Cherenkov radiation, and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. The photons of ultraviolet have greater energy than those of visible light, from about 3.1 to 12 electron volts, around the minimum energy required to ionize atoms. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack sufficient energy, it can induce chemical reactions and cause many substances to glow or fluoresce. Many practical applications, including chemical and biological effects, are derived from the way that UV radiation can interact with organic molecules. These i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Health Effects Of Sun Exposure
Exposure of skin to ultraviolet radiation from sunlight presents both positive and negative health effects. On the positive side, UV exposure enables the synthesis of vitamin D3, which is essential for bone health and potentially plays a role in inhibiting certain cancers. While vitamin D can also be obtained through dietary supplements, UV exposure offers benefits such as enhanced subdermal nitric oxide production and improved endorphin levels, which are not achievable through supplementation alone. Additionally, exposure to visible light supports melatonin synthesis, maintains circadian rhythms, and reduces the risk of seasonal affective disorder. However, UV radiation is also a mutagen and carcinogen for the skin, posing significant risks. Acute exposure can lead to painful sunburns and increase the likelihood of developing serious skin conditions later in life. Prolonged exposure is associated with the development of skin cancers, photoaging or premature skin aging, im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
