Skin
Details
Latin cutis
Identifiers
Code TH H3.12.00.1.00001
Anatomical terminology

The human skin is the outer covering of the body. In [1] Human skin is similar to that of most other mammals, except that it is not protected by a fur. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin, hairy and glabrous skin.[2] The adjective cutaneous literally means "of the skin" (from Latin cutis, skin).

Because it interfaces with the environment, skin plays a key immunity role in protecting the body against pathogens[3] and excessive water loss.[4] Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue. This is often discolored and depigmented.

In humans, skin pigmentation varies among populations, and skin type can range from dry to oily. Such skin variety provides a rich and diverse habitat for bacteria that number roughly 1000 species from 19 phyla.[5][6]

Structure

Skin has mesodermal cells, pigmentation, or melanin provided by melanocytes, which absorb some of the potentially dangerous ultraviolet radiation (UV) in sunlight. It also contains DNA repair enzymes that help reverse UV damage, such that people lacking the genes for these enzymes suffer high rates of skin cancer. One form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner. This has led to the classification of people(s) on the basis of skin color.[7]

The skin is the largest organ in the human body. For the average adult human, the skin has a surface area of between 1.5-2.0 square metres (16.1-21.5 sq ft.), most of it between 2–3 mm (0.10 inch) thick. The average square inch (6.5 cm²) of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings.[8]

Skin is composed of three primary layers:

Epidermis

Epidermis, "epi" coming from the Greek meaning "over" or "upon", is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous epithelium with an underlying basal lamina.

The epidermis contains no blood vessels, and cells in the deepest layers are nourished almost exclusively by diffused oxygen from the surrounding air[9] and to a far lesser degree by blood capillaries extending to the upper layers of the dermis. The main type of cells which make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, basale. Cells are formed through mitosis at the basale layer. The daughter cells (see cell division) move up the strata changing shape and composition as they die due to isolation from their blood source. The cytoplasm is released and the protein keratin is inserted. They eventually reach the corneum and slough off (desquamation). This process is called "keratinization". This keratinized layer of skin is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out, making skin a natural barrier to infection.

2D projection of a 3D OCT-tomogram of the skin at the fingertip, depicting the stratum corneum (~500 µm thick) with the stratum disjunctum on top and the stratum lucidum in the middle. At the bottom are the superficial parts of the dermis. The sweatducts are clearly visible. (See also: Rotating 3D Version)

Components

The epidermis contains no blood vessels, and is nourished by diffusion from the dermis. The main type of cells which make up the epidermis are keratinocytes, melanocytes, Langerhans cells and Merkels cells. The epidermis helps the skin to regulate body temperature.require('Module:No globals')

local p = {}

-- articles in which traditional Chinese preceeds simplified Chinese local t1st = { ["228 Incident"] = true, ["Chinese calendar"] = true, ["Lippo Centre, Hong Kong"] = true, ["Republic of China"] = true, ["Republic of China at the 1924 Summer Olympics"] = true, ["Taiwan"] = true, ["Taiwan (island)"] = true, ["Taiwan Province"] = true, ["Wei Boyang"] = true, }

-- the labels for each part local labels = { ["c"] = "Chinese", ["s"] = "simplified Chinese", ["t"] = "traditional Chinese", ["p"] = "pinyin", ["tp"] = "Tongyong Pinyin", ["w"] = "Wade–Giles", ["j"] = "Jyutping", ["cy"] = "Cantonese Yale", ["poj"] = "Pe̍h-ōe-jī", ["zhu"] = "Zhuyin Fuhao", ["l"] = "literally", }

-- article titles for wikilinks for each part local wlinks = { ["c"] = "Chinese language", ["s"] = "simplified Chinese characters", ["t"] = "traditional Chinese characters", ["p"] = "pinyin", ["tp"] = "Tongyong Pinyin", ["w"] = "Wade–Giles", ["j"] = "Jyutping", ["cy"] = "Yale romanization of Cantonese", ["poj"] = "Pe̍h-ōe-jī", ["zhu"] = "Bopomofo", }

-- for those parts which are to be treated as languages their ISO code local ISOlang = { ["c"] = "zh", ["t"] = "zh-Hant", ["s"] = "zh-Hans", ["p"] = "zh-Latn-pinyin", ["tp"] = "zh-Latn", ["w"] = "zh-Latn-wadegile", ["j"] = "yue-jyutping", ["cy"] = "yue", ["poj"] = "hak", ["zhu"] = "zh-Bopo", }

local italic = { ["p"] = true, ["tp"] = true, ["w"] = true, ["j"] = true, ["cy"] = true, ["poj"] = true, } -- Categories for different kinds of Chinese text local cats = { ["c"] = "", ["s"] = "", ["t"] = "", }

function p.Zh(frame) -- load arguments module to simplify handling of args local getArgs = require('Module:Arguments').getArgs local args = getArgs(frame) return p._Zh(args) end function p._Zh(args) local uselinks = not (args["links"] == "no") -- whether to add links local uselabels = not (args["labels"] == "no") -- whether to have labels local capfirst = args["scase"] ~= nil

        local t1 = false -- whether traditional Chinese characters go first
        local j1 = false -- whether Cantonese Romanisations go first
        local testChar
        if (args["first"]) then
                 for testChar in mw.ustring.gmatch(args["first"], "%a+") do
          if (testChar == "t") then
           t1 = true
           end
          if (testChar == "j") then
           j1 = true
           end
         end
        end
        if (t1 == false) then
         local title = mw.title.getCurrentTitle()
         t1 = t1st[title.text] == true
        end

-- based on setting/preference specify order local orderlist = {"c", "s", "t", "p", "tp", "w", "j", "cy", "poj", "zhu", "l"} if (t1) then orderlist[2] = "t" orderlist[3] = "s" end if (j1) then orderlist[4] = "j" orderlist[5] = "cy" orderlist[6] = "p" orderlist[7] = "tp" orderlist[8] = "w" end -- rename rules. Rules to change parameters and labels based on other parameters if args["hp"] then -- hp an alias for p ([hanyu] pinyin) args["p"] = args["hp"] end if args["tp"] then -- if also Tongyu pinyin use full name for Hanyu pinyin labels["p"] = "Hanyu Pinyin" end if (args["s"] and args["s"] == args["t"]) then -- Treat simplified + traditional as Chinese if they're the same args["c"] = args["s"] args["s"] = nil args["t"] = nil elseif (not (args["s"] and args["t"])) then -- use short label if only one of simplified and traditional labels["s"] = labels["c"] labels["t"] = labels["c"] end local body = "" -- the output string local params -- for creating HTML spans local label -- the label, i.e. the bit preceeding the supplied text local val -- the supplied text -- go through all possible fields in loop, adding them to the output for i, part in ipairs(orderlist) do if (args[part]) then -- build label label = "" if (uselabels) then label = labels[part] if (capfirst) then label = mw.language.getContentLanguage():ucfirst(

Layers

Epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called stratum corneum and are sloughed off, or desquamated. This process is called keratinization and takes place within weeks. The outermost layer of the epidermis consists of 25 to 30 layers of dead cells.

Sublayers

Epidermis is divided into the following 5 sublayers or strata:

Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule. Arterial shunt vessels may bypass the network in ears, the nose and fingertips.

Dermis

The dermis is the layer of skin beneath the epidermis that consists of epithelial tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many nerve endings that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as from the Stratum basale of the epidermis.

The dermis is structurally divided into two areas: a superficial area adjacent to the epidermis, called the papillary region, and a deep thicker area known as the reticular region.

Papillary region

The papillary region is composed of loose areolar connective tissue. It is named for its fingerlike projections called papillae, that extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin.

In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin's surface. These epidermal ridges occur in patterns (see: fingerprint) that are genetically and epigenetically determined and are therefore unique to the individual, making it possible to use fingerprints or footprints as a means of identification.

Reticular region

The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of collagenous, elastic, and reticular fibers that weave throughout it. These protein fibers give the dermis its properties of strength, extensibility, and elasticity.

Also located within the reticular region are the roots of the hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels.

Tattoo ink is held in the dermis. Stretch marks from pregnancy are also located in the dermis.

Hypodermis

The hypodermis is not part of the skin, and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue, adipose tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (the hypodermis contains 50% of body fat). Fat serves as padding and insulation for the body.

Cross-section

Skin layers, of both hairy and hairless skin

Development

Skin color

Human skin shows high skin color variety from the darkest brown to the lightest pinkish-white hues. Human skin shows higher variation in color than any other single mammalian species and is the result of natural selection. Skin pigmentation in humans evolved to primarily regulate the amount of ultraviolet radiation (UVR) penetrating the skin, controlling its biochemical effects.[10]

The actual skin color of different humans is affected by many substances, although the single most important substance determining human skin color is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skinned humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in the veins of the dermis. The red color underlying the skin becomes more visible, especially in the face, when, as consequence of physical exercise or the stimulation of the nervous system (anger, fear), arterioles dilate.[11]

There are at least five different pigments that determine the color of the skin.[12][13] These pigments are present at different levels and places.

  • Melanin: It is brown in color and present in the basal layer of the epidermis.
  • Melanoid: It resembles melanin but is present diffusely throughout the epidermis.
  • Carotene: This pigment is yellow to orange in color. It is present in the stratum corneum and fat cells of dermis and superficial fascia.
  • Hemoglobin (also spelled haemoglobin): It is found in blood and is not a pigment of the skin but develops a purple color.
  • Oxyhemoglobin: It is also found in blood and is not a pigment of the skin. It develops a red color.

There is a correlation between the geographic distribution of UV radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that highlight higher amounts of UVR reflect darker-skinned populations, generally located nearer towards the equator. Areas that are far from the tropics and closer to the poles have lower concentration of UVR, which is reflected in lighter-skinned populations.[14]

In the same population it has been observed that adult human females are considerably lighter in skin pigmentation than males. Females need more calcium during pregnancy and lactation and vitamin D which is synthesized from sunlight helps in absorbing calcium. For this reason it is thought that females may have evolved to have lighter skin in order to help their bodies absorb more calcium.[15]

The Fitzpatrick scale[16][17] is a numerical classification schema for human skin color developed in 1975 as a way to classify the typical response of different types of skin to ultraviolet (UV) light:
I Always burns, never tans Pale, Fair, Freckles
II Usually burns, sometimes tans Fair
III May burn, usually tans Light Brown
IV Rarely burns, always tans Olive brown
V Moderate constitutional pigmentation Brown
VI Marked constitutional pigmentation Black

Aging

A typical rash
Skin infected with Scabies

As skin ages, it becomes thinner and more easily damaged. Intensifying this effect is the decreasing ability of skin to heal itself as a person ages.

Among other things, skin aging is noted by a decrease in volume and elasticity. There are many internal and external causes to skin aging. For example, aging skin receives less blood flow and lower glandular activity.

A validated comprehensive grading scale has categorized the clinical findings of skin aging as laxity (sagging), rhytids (wrinkles), and the various facets of photoaging, including erythema (redness), and telangiectasia, dyspigmentation (brown discoloration), solar elastosis (yellowing), keratoses (abnormal growths) and poor texture.[18]

Cortisol causes degradation of collagen,[19] accelerating skin aging.[20]

Anti-aging supplements are used to treat skin aging.

Photoaging

Photoaging has two main concerns: an increased risk for skin cancer and the appearance of damaged skin. In younger skin, sun damage will heal faster since the cells in the epidermis have a faster turnover rate, while in the older population the skin becomes thinner and the epidermis turnover rate for cell repair is lower which may result in the dermis layer being damaged.[21]

Functions

Skin performs the following functions:

  1. Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system.[3][4]
  2. Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury; see somatosensory system and haptics.
  3. Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heatloss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.
  4. Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss.[4] Loss of this function contributes to the massive fluid loss in burns.
  5. Aesthetics and communication: others see our skin and can assess our mood, physical state and attractiveness.
  6. Storage and synthesis: acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin.
  7. Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation.
  8. Absorption: the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is negligible".[9] In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in many other organisms.
  9. Water resistance: The skin acts as a water resistant barrier so essential nutrients aren't washed out of the body.

Skin flora

The human skin is a rich environment for microbes.[5][6] Around 1000 species of bacteria from 19 bacterial phyla have been found. Most come from only four phyla: Actinobacteria (51.8%), Firmicutes (24.4%), Proteobacteria (16.5%), and Bacteroidetes (6.3%). Propionibacteria and Staphylococci species were the main species in sebaceous areas. There are three main ecological areas: moist, dry and sebaceous. In moist places on the body Corynebacteria together with Staphylococci dominate. In dry areas, there is a mixture of species but dominated by b-Proteobacteria and Flavobacteriales. Ecologically, sebaceous areas had greater species richness than moist and dry ones. The areas with least similarity between people in species were the spaces between fingers, the spaces between toes, axillae, and umbilical cord stump. Most similarly were beside the nostril, nares (inside the nostril), and on the back.

Reflecting upon the diversity of the human skin researchers on the human skin microbiome have observed: "hairy, moist underarms lie a short distance from smooth dry forearms, but these two niches are likely as ecologically dissimilar as rainforests are to deserts."[5]

The NIH has launched the Human Microbiome Project to characterize the human microbiota which includes that on the skin and the role of this microbiome in health and disease.[22]

Microorganisms like Staphylococcus epidermidis colonize the skin surface. The density of skin flora depends on region of the skin. The disinfected skin surface gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital openings.

Clinical significance

Diseases of the skin include skin infections and skin neoplasms (including skin cancer).

Dermatology is the branch of medicine that deals with conditions of the skin.[2]

Society and culture

Hygiene and skin care

The skin supports its own antibiotics kill microbes, resulting in an overgrowth of yeast. The skin is continuous with the inner epithelial lining of the body at the orifices, each of which supports its own complement of microbes.

Cosmetics should be used carefully on the skin because these may cause allergic reactions. Each season requires suitable clothing in order to facilitate the evaporation of the sweat. Sunlight, water and air play an important role in keeping the skin healthy.

Oily skin

Oily skin is caused by over-active sebaceous glands, that produce a substance called sebum, a naturally healthy skin lubricant.[1] When the skin produces excessive sebum, it becomes heavy and thick in texture. Oily skin is typified by shininess, blemishes and pimples.[1] The oily-skin type is not necessarily bad, since such skin is less prone to wrinkling, or other signs of aging,[1] because the oil helps to keep needed moisture locked into the epidermis (outermost layer of skin).

The negative aspect of the oily-skin type is that oily complexions are especially susceptible to clogged pores, blackheads, and buildup of dead skin cells on the surface of the skin.[1] Oily skin can be sallow and rough in texture and tends to have large, clearly visible pores everywhere, except around the eyes and neck.[1]

Permeability

Human skin has a low [24][25] This protects the body from external particles such as toxins by not allowing them to come into contact with internal tissues. However, in some cases it is desirable to allow particles entry to the body through the skin. Potential medical applications of such particle transfer has prompted developments in nanomedicine and biology to increase skin permeability. One application of transcutaneous particle delivery could be to locate and treat cancer. Nanomedical researchers seek to target the epidermis and other layers of active cell division where nanoparticles can interact directly with cells that have lost their growth-control mechanisms (cancer cells). Such direct interaction could be used to more accurately diagnose properties of specific tumors or to treat them by delivering drugs with cellular specificity.

Nanoparticles

Nanoparticles 40 nm in diameter and smaller have been successful in penetrating the skin.[26][27][28] Research confirms that nanoparticles larger than 40 nm do not penetrate the skin past the stratum corneum.[26] Most particles that do penetrate will diffuse through skin cells, but some will travel down hair follicles and reach the dermis layer.

The permeability of skin relative to different shapes of nanoparticles has also been studied. Research has shown that spherical particles have a better ability to penetrate the skin compared to oblong (ellipsoidal) particles because spheres are symmetric in all three spatial dimensions.[28] One study compared the two shapes and recorded data that showed spherical particles located deep in the epidermis and dermis whereas ellipsoidal particles were mainly found in the stratum corneum and epidermal layers.[29] Nanorods are used in experiments because of their unique fluorescent properties but have shown mediocre penetration.

Nanoparticles of different materials have shown skin’s permeability limitations. In many experiments, gold nanoparticles 40 nm in diameter or smaller are used and have shown to penetrate to the epidermis. polyethylene glycol (PEG), PEG-amine, and carboxylic acid concluded the PEG and PEG-amine surface groups allowed for the greatest penetration of particles. The carboxylic acid coated particles did not penetrate past the stratum corneum.[29]

Increasing permeability

Scientists previously believed that the skin was an effective barrier to inorganic particles. Damage from mechanical stressors was believed to be the only way to increase its permeability.[32] Recently, however, simpler and more effective methods for increasing skin permeabiltiy have been developed. For example, ultraviolet radiation (UVR) has been used to slightly damage the surface of skin, causing a time-dependent defect allowing easier penetration of nanoparticles.[33] The UVR’s high energy causes a restructuring of cells, weakening the boundary between the stratum corneum and the epidermal layer.[34][33] The damage of the skin is typically measured by the transepidermal water loss (TEWL), though it may take 3–5 days for the TEWL to reach its peak value. When the TEWL reaches its highest value, the maximum density of nanoparticles is able to permeate the skin. Studies confirm that UVR damaged skin significantly increases the permeability.[34][33] The effects of increased permeability after UVR exposure can lead to an increase in the number of particles that permeate the skin. However, the specific permeability of skin after UVR exposure relative to particles of different sizes and materials has not been determined.[33]

Other skin damaging methods used to increase nanoparticle penetration include tape stripping, skin abrasion, and chemical enhancement. Tape stripping is the process in which tape is applied to skin then lifted to remove the top layer of skin. Skin abrasion is done by shaving the top 5-10 micrometers off the surface of the skin. Chemical enhancement is the process in which chemicals such as polyvinylpyrrolidone (PVP), dimethyl sulfoxide (DMSO), and oleic acid are applied to the surface of the skin to increase permeability.[35][36]

Electroporation is the application of short pulses of electric fields on skin and has proven to increase skin permeability. The pulses are high voltage and on the order of milliseconds when applied. Charged molecules penetrate the skin more frequently than neutral molecules after the skin has been exposed to electric field pulses. Results have shown molecules on the order of 100 micrometers to easily permeate electroporated skin.[36]

Applications

A large area of interest in nanomedicine is the transdermal patch because of the possibility of a painless application of therapeutic agents with very few side effects. Transdermal patches have been limited to administer a small number of drugs, such as nicotine, because of the limitations in permeability of the skin. Development of techniques that increase skin permeability has led to more drugs that can be applied via transdermal patches and more options for patients.[36]

Increasing the permeability of skin allows nanoparticles to penetrate and target cancer cells. Nanoparticles along with multi-modal imaging techniques have been used as a way to diagnose cancer non-invasively. Skin with high permeability allowed quantum dots with an antibody attached to the surface for active targeting to successfully penetrate and identify cancerous tumors in mice. Tumor targeting is beneficial because the particles can be excited using fluorescence microscopy and emit light energy and heat that will destroy cancer cells.[37]

Sunblock and sunscreen

Sunblock and sunscreen are different important skin-care products though both offer full protection from the sun.[38][39]

SunblockSunblock is opaque and stronger than sunscreen, since it is able to block most of the UVA/UVB rays and radiation from the sun, and does not need to be reapplied several times in a day. Titanium dioxide and zinc oxide are two of the important ingredients in sunblock.[40]

SunscreenSunscreen is more transparent once applied to the skin and also has the ability to protect against UVA/UVB rays as well, although the sunscreen's ingredients have the ability to break down at a faster rate once exposed to sunlight, and some of the radiation is able to penetrate to the skin. In order for sunscreen to be more effective it is necessary to consistently reapply and use one with a higher sun protection factor.

Diet

Vitamin A, also known as retinoids, benefits the skin by normalizing keratinization, downregulating sebum production which contributes to acne, and reversing and treating photodamage, striae, and cellulite.

Vitamin D and analogs are used to downregulate the cutaneous immune system and epithelial proliferation while promoting differentiation.

Vitamin C is an antioxidant that regulates collagen synthesis, forms barrier lipids, regenerates vitamin E, and provides photoprotection.

Vitamin E is a membrane antioxidant that protects against oxidative damage and also provides protection against harmful UV rays. [41]

Several scientific studies confirmed that changes in baseline nutritional status affects skin condition. [42]

The Mayo Clinic lists foods they state help the skin: yellow, green, and orange fruits and vegetables; fat-free dairy products; whole-grain foods; fatty fish, nuts.[43]

See also

References


-- Module:Hatnote -- -- -- -- This module produces hatnote links and links to related articles. It -- -- implements the and meta-templates and includes -- -- helper functions for other Lua hatnote modules. --


local libraryUtil = require('libraryUtil') local checkType = libraryUtil.checkType local mArguments -- lazily initialise Module:Arguments local yesno -- lazily initialise Module:Yesno

local p = {}


-- Helper functions


local function getArgs(frame) -- Fetches the arguments from the parent frame. Whitespace is trimmed and -- blanks are removed. mArguments = require('Module:Arguments') return mArguments.getArgs(frame, {parentOnly = true}) end

local function removeInitialColon(s) -- Removes the initial colon from a string, if present. return s:match('^:?(.*)') end

function p.findNamespaceId(link, removeColon) -- Finds the namespace id (namespace number) of a link or a pagename. This -- function will not work if the link is enclosed in double brackets. Colons -- are trimmed from the start of the link by default. To skip colon -- trimming, set the removeColon parameter to true. checkType('findNamespaceId', 1, link, 'string') checkType('findNamespaceId', 2, removeColon, 'boolean', true) if removeColon ~= false then link = removeInitialColon(link) end local namespace = link:match('^(.-):') if namespace then local nsTable = mw.site.namespaces[namespace] if nsTable then return nsTable.id end end return 0 end

function p.formatPages(...) -- Formats a list of pages using formatLink and returns it as an array. Nil -- values are not allowed. local pages = {...} local ret = {} for i, page in ipairs(pages) do ret[i] = p._formatLink(page) end return ret end

function p.formatPageTables(...) -- Takes a list of page/display tables and returns it as a list of -- formatted links. Nil values are not allowed. local pages = {...} local links = {} for i, t in ipairs(pages) do checkType('formatPageTables', i, t, 'table') local link = t[1] local display = t[2] links[i] = p._formatLink(link, display) end return links end

function p.makeWikitextError(msg, helpLink, addTrackingCategory) -- Formats an error message to be returned to wikitext. If -- addTrackingCategory is not false after being returned from -- Module:Yesno, and if we are not on a talk page, a tracking category -- is added. checkType('makeWikitextError', 1, msg, 'string') checkType('makeWikitextError', 2, helpLink, 'string', true) yesno = require('Module:Yesno') local title = mw.title.getCurrentTitle() -- Make the help link text. local helpText if helpLink then helpText = ' (help)' else helpText = end -- Make the category text. local category if not title.isTalkPage and yesno(addTrackingCategory) ~= false then category = 'Hatnote templates with errors' category = string.format( '%s:%s', mw.site.namespaces[14].name, category ) else category = end return string.format( '%s', msg, helpText, category ) end


-- Format link -- -- Makes a wikilink from the given link and display values. Links are escaped -- with colons if necessary, and links to sections are detected and displayed -- with " § " as a separator rather than the standard MediaWiki "#". Used in -- the template.


function p.formatLink(frame) local args = getArgs(frame) local link = args[1] local display = args[2] if not link then return p.makeWikitextError( 'no link specified', 'Template:Format hatnote link#Errors', args.category ) end return p._formatLink(link, display) end

function p._formatLink(link, display) -- Find whether we need to use the colon trick or not. We need to use the -- colon trick for categories and files, as otherwise category links -- categorise the page and file links display the file. checkType('_formatLink', 1, link, 'string') checkType('_formatLink', 2, display, 'string', true) link = removeInitialColon(link) local namespace = p.findNamespaceId(link, false) local colon if namespace == 6 or namespace == 14 then colon = ':' else colon = end -- Find whether a faux display value has been added with the | magic -- word. if not display then local prePipe, postPipe = link:match('^(.-)|(.*)$') link = prePipe or link display = postPipe end -- Find the display value. if not display then local page, section = link:match('^(.-)#(.*)$') if page then display = page .. ' § ' .. section end end -- Assemble the link. if display then return string.format('%s', colon, link, display) else return string.format('%s%s', colon, link) end end


-- Hatnote -- -- Produces standard hatnote text. Implements the template.


function p.hatnote(frame) local args = getArgs(frame) local s = args[1] local options = {} if not s then return p.makeWikitextError( 'no text specified', 'Template:Hatnote#Errors', args.category ) end options.extraclasses = args.extraclasses options.selfref = args.selfref return p._hatnote(s, options) end

function p._hatnote(s, options) checkType('_hatnote', 1, s, 'string') checkType('_hatnote', 2, options, 'table', true) local classes = {'hatnote'} local extraclasses = options.extraclasses local selfref = options.selfref if type(extraclasses) == 'string' then classes[#classes + 1] = extraclasses end if selfref then classes[#classes + 1] = 'selfref' end return string.format( '
%s
', table.concat(classes, ' '), s )

end

return p-------------------------------------------------------------------------------- -- Module:Hatnote -- -- -- -- This module produces hatnote links and links to related articles. It -- -- implements the and meta-templates and includes -- -- helper functions for other Lua hatnote modules. --


local libraryUtil = require('libraryUtil') local checkType = libraryUtil.checkType local mArguments -- lazily initialise Module:Arguments local yesno -- lazily initialise Module:Yesno

local p = {}


-- Helper functions


local function getArgs(frame) -- Fetches the arguments from the parent frame. Whitespace is trimmed and -- blanks are removed. mArguments = require('Module:Arguments') return mArguments.getArgs(frame, {parentOnly = true}) end

local function removeInitialColon(s) -- Removes the initial colon from a string, if present. return s:match('^:?(.*)') end

function p.findNamespaceId(link, removeColon) -- Finds the namespace id (namespace number) of a link or a pagename. This -- function will not work if the link is enclosed in double brackets. Colons -- are trimmed from the start of the link by default. To skip colon -- trimming, set the removeColon parameter to true. checkType('findNamespaceId', 1, link, 'string') checkType('findNamespaceId', 2, removeColon, 'boolean', true) if removeColon ~= false then link = removeInitialColon(link) end local namespace = link:match('^(.-):') if namespace then local nsTable = mw.site.namespaces[namespace] if nsTable then return nsTable.id end end return 0 end

function p.formatPages(...) -- Formats a list of pages using formatLink and returns it as an array. Nil -- values are not allowed. local pages = {...} local ret = {} for i, page in ipairs(pages) do ret[i] = p._formatLink(page) end return ret end

function p.formatPageTables(...) -- Takes a list of page/display tables and returns it as a list of -- formatted links. Nil values are not allowed. local pages = {...} local links = {} for i, t in ipairs(pages) do checkType('formatPageTables', i, t, 'table') local link = t[1] local display = t[2] links[i] = p._formatLink(link, display) end return links end

function p.makeWikitextError(msg, helpLink, addTrackingCategory) -- Formats an error message to be returned to wikitext. If -- addTrackingCategory is not false after being returned from -- Module:Yesno, and if we are not on a talk page, a tracking category -- is added. checkType('makeWikitextError', 1, msg, 'string') checkType('makeWikitextError', 2, helpLink, 'string', true) yesno = require('Module:Yesno') local title = mw.title.getCurrentTitle() -- Make the help link text. local helpText if helpLink then helpText = ' (help)' else helpText = end -- Make the category text. local category if not title.isTalkPage and yesno(addTrackingCategory) ~= false then category = 'Hatnote templates with errors' category = string.format( '%s:%s', mw.site.namespaces[14].name, category ) else category = end return string.format( '%s', msg, helpText, category ) end


-- Format link -- -- Makes a wikilink from the given link and display values. Links are escaped -- with colons if necessary, and links to sections are detected and displayed -- with " § " as a separator rather than the standard MediaWiki "#". Used in -- the template.


function p.formatLink(frame) local args = getArgs(frame) local link = args[1] local display = args[2] if not link then return p.makeWikitextError( 'no link specified', 'Template:Format hatnote link#Errors', args.category ) end return p._formatLink(link, display) end

function p._formatLink(link, display) -- Find whether we need to use the colon trick or not. We need to use the -- colon trick for categories and files, as otherwise category links -- categorise the page and file links display the file. checkType('_formatLink', 1, link, 'string') checkType('_formatLink', 2, display, 'string', true) link = removeInitialColon(link) local namespace = p.findNamespaceId(link, false) local colon if namespace == 6 or namespace == 14 then colon = ':' else colon = end -- Find whether a faux display value has been added with the | magic -- word. if not display then local prePipe, postPipe = link:match('^(.-)|(.*)$') link = prePipe or link display = postPipe end -- Find the display value. if not display then local page, section = link:match('^(.-)#(.*)$') if page then display = page .. ' § ' .. section end end -- Assemble the link. if display then return string.format('%s', colon, link, display) else return string.format('%s%s', colon, link) end end


-- Hatnote -- -- Produces standard hatnote text. Implements the template.


function p.hatnote(frame) local args = getArgs(frame) local s = args[1] local options = {} if not s then return p.makeWikitextError( 'no text specified', 'Template:Hatnote#Errors', args.category ) end options.extraclasses = args.extraclasses options.selfref = args.selfref return p._hatnote(s, options) end

function p._hatnote(s, options) checkType('_hatnote', 1, s, 'string') checkType('_hatnote', 2, options, 'table', true) local classes = {'hatnote'} local extraclasses = options.extraclasses local selfref = options.selfref if type(extraclasses) == 'string' then classes[#classes + 1] = extraclasses end if selfref then classes[#classes + 1] = 'selfref' end return string.format( '
%s
', table.concat(classes, ' '), s )

end

return p
  1. ^ a b c d e f "Skin care" (analysis), Health-Cares.net, 2007, webpage: HCcare
  2. ^ a b Marks, James G; Miller, Jeffery (2006). Lookingbill and Marks' Principles of Dermatology. (4th ed.). Elsevier Inc. ISBN 1-4160-3185-5.
  3. ^ a b
  4. ^ a b c
  5. ^ a b c
  6. ^ a b Pappas S. (2009). Your Body Is a Wonderland ... of Bacteria. ScienceNOW Daily News
  7. ^
  8. ^
  9. ^ a b
  10. ^
  11. ^
  12. ^ Handbook of General Anatomy by B. D. Chaurasia. ISBN 978-81-239-1654-5
  13. ^ Pigmentation of Skin
  14. ^
  15. ^
  16. ^
  17. ^
  18. ^ Alexiades-Armenakas, M. R., et al. The spectrum of laser skin resurfacing: nonablative, fractional, and ablative laser resurfacing. J Am Acad Dermatol. 2008 May;58(5):719-37; quiz 738-40
  19. ^ (subscription required)
  20. ^ (subscription required)
  21. ^
  22. ^ NIH Human Microbiome Project.
  23. ^ Theodor Rosebury. Life on Man: Secker & Warburg, 1969 ISBN 0-670-42793-4
  24. ^
  25. ^
  26. ^ a b
  27. ^
  28. ^ a b
  29. ^ a b Ryman-Rasmussen, J.P., Riviere, J.E. and Monteiro-Riviere, N.A. Penetration of Intact Skin by Quantum Dots with Diverse Physicochemical Properties. Toxicological Sciences 2006;91(1):159-165
  30. ^ Felipe, P., Silva, J.N., Silva, R., Cirne de Castro, J.L., Gomes, M., Alves, L.C., et al. Stratum Corneum Is an Effective Carrier to TiO2 and ZnO Nanoparticle Percutaneous Absorption. Skin Pharmacology and Physiology 2009;22:266-275
  31. ^
  32. ^
  33. ^ a b c d
  34. ^ a b Mortensen, L., Oberdorster, G., Pentland, A. and DeLoiuse, L. In Vivo Skin Penetration of Quantum Dot Nanoparticles in the Murine Model: The Effects of UVR" Nano Letters 2008;8(9) 2779-2787
  35. ^ Sokolov, K., Follen M., Aaron, J., Pavlova, I., Malpica, A., Lotan, R., et al. Real-Time Vital Optical Imaging of Precancer Using Anti-Epidermal Growth Factor Receptor Antibodies Conjugated to Gold Nanoparticles" Cancer Research 2003 May;63:199
  36. ^ a b c Prausnitz, M., Mitragotri, S. and Langer, R. Current Status and Future Potential of Transdermal Drug Delivery. Drug Discovery 2004 February;3:115-124
  37. ^ Gao, X., Cui, Y., Levenson, R., Chung, L. and Nie, S. In vivo cancer targeting and imaging with semiconductor quantum dots. Nature Biotechnology 2005;22(8):969-976
  38. ^
  39. ^ An update on Suncreens; 2007; P 23- 29. Available at www.aocd.org/resource/resmgr/jaocd/2007aug.pdf
  40. ^
  41. ^
  42. ^ [1]
  43. ^ http://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/healthy-skin/faq-20058184

External links

  • MedlinePlus Skin Conditions National Library of Medicine retrieved November 12, 2013.