What is Skin: Definition and 157 Discussions

Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.Other animal coverings, such as the arthropod exoskeleton, have different developmental origin, structure and chemical composition. The adjective cutaneous means "of the skin" (from Latin cutis 'skin'). In mammals, the skin is an organ of the integumentary system made up of multiple layers of ectodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, and birds. Skin (including cutaneous and subcutaneous tissues) plays crucial roles in formation, structure and function of extra-skeletal apparatus such as horns of bovids [e.g. cattle] and rhinos, cervids' antlers, giraffids' ossicones, armadillos' osteoderm, and os penis/ os clitoris.All mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises which appear to be hairless.
The skin interfaces with the environment and is the first line of defense from external factors. For example, the skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, and the production of vitamin D folates. Severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented. The thickness of skin also varies from location to location on an organism. In humans for example, the skin located under the eyes and around the eyelids is the thinnest skin in the body at 0.5 mm thick, and is one of the first areas to show signs of aging such as "crows feet" and wrinkles. The skin on the palms and the soles of the feet is 4 mm thick and is the thickest skin on the body. The speed and quality of wound healing in skin is promoted by the reception of estrogen.Fur is dense hair. Primarily, fur augments the insulation the skin provides but can also serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is very hard and thick, and can be processed to create leather. Reptiles and most fish have hard protective scales on their skin for protection, and birds have hard feathers, all made of tough beta-keratins. Amphibian skin is not a strong barrier, especially regarding the passage of chemicals via skin and is often subject to osmosis and diffusive forces. For example, a frog sitting in an anesthetic solution would be sedated quickly, as the chemical diffuses through its skin. Amphibian skin plays key roles in everyday survival and their ability to exploit a wide range of habitats and ecological conditions.

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  1. S

    What do large moles on the body indicate?

    People usually dislike people with big birthmarks (I mostly mean sexual attractiveness, but not only). It seems that the presence of moles correlate with something bad in the organism. With what? Is that possibly that the moles can correlate with bad features of character? I have found the...
  2. DaveC426913

    Nail Growth: How Skin Under Nails Moves

    I feel 12 years old asking this. Your nails grow. Isn't the skin attached to the underside of the nail? Why doesn't it pile up at your finger tips? It doesn't, so that must mean your nail slides over the skin like a glacier over land?
  3. Buzz Bloom

    Medical An Odd Description of Skin Cancer Cause from UV Radiation

    Scientific American June 2, 2022 Vol 32 Number 6 Page 62 Title: Skin Cancer around the World Two Quotes: “The main cause of skin cancer is the exposure to the sun’s ultraviolet rays…” “UV radiation is about 40% stronger in New Zealand than it is at corresponding latitudes in the Northern...
  4. bluesteels

    Quick question about the heat Q transferred between water and skin

    My work Q= 0.025 * 4190 * (34-100) = -6910 but on chegg but did they do Q= 0.025 * 4190 * (100-34) = 6910. I thought the initial is 100C and final is 34 because it goes from 100 to 34
  5. B

    In Vibroacoustic Therapy does the transducers have to be on the skin ?

    In vibroacoustic therapy does the transducers have to be touching the skin ? I get that power is lost in the air, but it is enough to matter ?
  6. Narayanan KR

    A Question on Skin Effect and Eddy Currents

    When you try to create time varying magnetic fields in solid metals, there is severe heating due to eddy currents, when you increase the frequency, just like in NDT(non destructive testing) the magnetic field is pushed away from the core to the periphery due to eddy currents opposing the field...
  7. D

    Engineering Over-consolidation pressure / negative skin friction of clay

    However, I can't find any proof on this ? Can someone help to explain this ?
  8. T

    Skin depth of multilayered (2-layer) wire

    Homework Statement:: Not a specific question, more just a conceptual clarification for a project. But generally: What is an equation for the effective skin depth of a multilayered (in this case only 2 layers) wire, as a function of the resistivities and relative permeabilities of both of the...
  9. iVenky

    I Is London depth in superconductors analogous to skin depth?

    London penetration depth that's defined for superconductors has a similar equation to skin depth in conductors derived from maxwell's equations. Are they equivalent?
  10. C

    Is the skin depth of tarnished silver any different than untarnished?

    That's it, just the question. I am figuring that the tarnish is an irrelevance as it does not participate either magnetically or electrically, so any RF current passing through the [still metallic] silver top layer, albeit with tarnish over the top, will pass through the same thickness of...
  11. mark!

    Is a black skin related to melanin's relation with adrenaline?

    Why is it generally accepted that black skin is only caused by melanin, due to the intensity of UV radiation, in order to protect the body from skin cancer to develop? Because melanin is also, together with adrenaline, linked to the precursor: dopamine, thus both chemicals share the same pathway...
  12. T

    Is this urban legend about clams and oysters true? (men's skin)

    I herd about this, is it true. Is eating clams or oysters good for mens skin?
  13. Zachrz

    Safe Endothermic reactions for skin

    Hi, Its my first time here in PF, I was wondering what could be a fast endothermic reaction(with water) that does not burn the skin/ cause severe allergic reactions when/after touching or in contact with the reaction. (With high rate of cooling and hopefully no bubbles or gas forming). E.g to be...
  14. Sophrosyne

    The physics of eye and skin color

    I was reading about why blue eyes look blue. After all, the human body does not create any blue pigment. It turns out, it's the same reason the sky is blue: the Tyndall effect. When there is minimal pigmentation, the first frequencies of light to scatter are the blue frequency waves. When there...
  15. X

    A Powder XRD sample prep question

    Hello, I have an unusual case in that I am using XRD to study plant skins before and after certain chemical treatments. So the resulting pattern will have a lot of amorphous regions but also some characteristic peaks showing the presence of fatty acids, etc. Basically I grind everything to a...
  16. P

    Hydrogen bonding in human skin

    if the human skin consists of hydrogen, then why does not happen hydrogen bond through contact with something or with another person?
  17. R

    Does moisture increase friction on skin?

    This may be one of those things that everybody knew but me (come to think of it, I think I'll add it to the "things I learned today" thread elsewhere). There are some plastic bags I use which come on a roll. I have been struggling to open them when I remove a bag from the roll, rubbing...
  18. K

    Can Splinters and Fillings Join the Bloodstream?

    If you have fillings (such as from iron dusts or carbon fiber) stuck in your skin? would it eventually join with your blood flow? What is the filter system of the blood where it couldn't accept the smallest particle and how big is the particle? Imagine iron dust filling or 1 carbon fiber...
  19. Bystander

    Medical Is the New Skin Commercial's Brush Applicator Unsanitary?

    Has anyone got thoughts/opinions on the brush applicator for the product being a bit unsanitary? Just saw it, and the cut in the model's hand is being "painted" shut/closed with a brush that is obviously being returned to the bottle. Is there not potential for wound fluid(s) to...
  20. G

    Skin effect and electric shock question

    recently i saw a thread where skin depth was mentioned (I guess in one of my own threads) and then it got me thinking, well imagine we have a rather thick wire thick enough so that for a given frequency there is almost no current running in the middle of the wire due to skin effect. let's take...
  21. C

    I What is meant by "low frequencies"? (EM skin depth question)

    I'm studying conductors, where complex wave number ##K=k+iα## and complex index of refraction ##N=n+iκ## is introduced. My textbook(Fowles Optics) says that for "very low frequencies", skin depth δ is equal to ##δ=\frac{1}{α}=\sqrt{\frac{λ_0}{cπσμ_0}}##. What is "very low frequency"? How much...
  22. F

    Skin temperature increase due to radiation absorption

    Hello, I am trying to figure out how much the human skin temperature would increase when the skin is illuminated by radiation of a certain intensity (W/m^2). We can assume that the skin has an emissivity and absorptivity both equal to 1. For instance, imagine the skin illuminated by the sun (I=...
  23. D

    Strange question:which chemicals cause skin reactions

    A little complicated and interesting story, I will get down to the point: I need a number of substances that cause skin rashes/skin redness or overall has a bad reaction to human skin. This is all for research purposes for natural skin products me and a group of friends are developing.
  24. Jackson Lee

    Why Does the Skin Effect Not Reverse into a Core Effect in AC Conductors?

    Hey, guys. There is something interesting about the skin effect, which also made me curious:wink:. Could you please help to solve it? The following is what I got from Wiki. It is said that, according to theory of induction, induced current would oppose the change of magnetic field. Then when...
  25. I

    Is there a common name for protective layer of an organism?

    Hello, is there a common name/word/terminology for any protective layers on an organism, for example, skin on humans, bark on a tree, etc?
  26. E

    Maximizing Wattage in DIY Heaters: Impedance Matching with ZVS Power Supply

    Hi folks, I want to build a heater similar to this http://www.thermon.com/us/products.aspx?prodid=10 , using a ZVS power supply from ebay (such as this one -http://www.ebay.com/itm/381569526996?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) ) As well I would like to replace...
  27. mertcan

    The Logic Behind Equating Differential Operators to Numbers in Electromagnetism

    hi, nowadays I try to get involved electromagnetic waves equations, and I came across that $$ \nabla $$ is treated like $$ ik $$ and $$ \frac {\partial } {\partial t} $$ is treated like $$ -iw $$ And if you look at the part painted with orange in my attachment, afterwards you can see that $$...
  28. S

    Which Skin Colour Distribution Map is Most Reliable?

    I see 2 commonly quoted maps for distribution of native human skin colour. Both are old; they have a lot of odd divergences - as well as many matching features, some of which are hard to explain. One is Biasutti, 1940: https://upload.wikimedia.org/wikipedia/commons/8/81/Map_of_skin_hue_equi.png...
  29. T

    Skin effect and magnetic field of a flattened conductor?

    A conductor with a large high frequency AC current causes a "Skin Effect" meaning that most of the current flows at the surface of the conductor. What does the skin effect look like if you have a conductor with one side flattened? And what does the resulting magnetic field look like? See...
  30. Anton Alice

    I What is the connection between the skin effect and electromagnetic waves?

    First of all, hello. I have a problem in understanding the skin effect. Often I read, that the skin effect is directly caused by eddy fields inside the conductor, which oppose the "desired" current flow. Problem at this is, that the eddy fields are not in phase with the desired current. The...
  31. Docscientist

    Which is more harmful to skin?

    Homework Statement Amoung soap and detergent,which is more harmful to our skin? Homework Equations None The Attempt at a Solution Soap is what we use for bathing so if it is harmful we wouldn't have used it.The detergents are used for washing clothes more often. So I think detergents are harmful.
  32. T

    EM wave shielding & skin depth

    If I use 10mm (thickness) of a metal for the sides of a Faraday cage, with a 5mm skin depth at the frequency to be shielded, & increase the v/m of the EM wave to be blocked gradually, will there be a stage where the skin depth will increase to 6mm, or is 5mm the maximum limit?
  33. D

    Can skin be positively or negatively charged?

    Is it possible for skin to hold a negative or positive charge on one part of the body, such as the back of a hand? How does this occur? Thank you
  34. E

    Materials to make skin friction negligible

    Hi, I need to run wind tunnel tests on a simple shape which will be made of foam whilst the skin friction is to be negligible. Is there easy ways of cover the model to achieve this ? thanks
  35. W

    Skin depth: Same for current as for incoming EM wave?

    For a good conductor, an incoming plane electromagnetic wave will be attenuated exponentially as it penetrates a distance ##z## into the conductor, ##|\vec{E}(z)| = |\vec{E_0}|e^{-z/ \delta}##. ##\delta## is called the "skin depth". The current generated by this incoming electromagnetic wave is...
  36. finnch

    UVA vs UVB: Why does UVA penetrate deeper into the skin?

    Hello, My name is Chris and I am trying to understand why UVA radiation, with a longer wavelength, penetrates deeper into the skin than UVB which has a shorter wavelength. Since E=hv=hc/ λ and , then how does a lower energy and lower intensity UVA wave penetrate deeper into the skin than a...
  37. finnch

    UVA/UVB Light: Why does UVA penetrate deeper into the skin?

    [Mentor's Note: Thread moved from New Member Introductions] Hello, My name is Chris and I am trying to understand why UVA radiation, with a longer wavelength, penetrates deeper into the skin than UVB which has a shorter wavelength. Since E=hv=hc/ λ and then how does a lower energy...

    How to join honeycomb and skin in ansys apdl for sandwich structure

    I modeled honeycomb core and face sheet seperately now i want to add or glue them to make a sandwich but it shows error so how can i join them.anyone please
  39. P

    Evolving with skin stronger than bone

    Is it possible for an organism to evolve with skin stronger than bone? theoretically? As in, a humanoid only instead of strong bones, it has strong skin? Would that make sense biologically? Thank you for any aid!
  40. P

    Pressures indenting surfaces that are stone, metal or skin

    Hello everyone, thank you for helping me in the other post, this one is different but includes pressure and how to calculate how much of it is present when an object is being "indented" or dug into. I come from a forum that discusses fictional characters a lot and we find it highly enjoyable to...
  41. G

    Understanding Skin Depth in DC and AC Fields: Confusion and Clarification

    Hello. The skin depth is nothing but measure of penetration depth of EM Wave when it is incident on the conductor. It is well known that the skin depth is decreased when the EM wave frequency increases. But thinking about DC field. We know that when DC is applied to metal (metal is installed...
  42. beowulf.geata

    Current density and skin depth

    Homework Statement A thin metallic strip on a circuit board has length L, width a and thickness t, with L>>a>> t. Derive an expression for the resistance between the ends of the strip at frequency f, assuming that the skin depth is small compared with the thickness t. Homework Equations The...
  43. P

    Skin effect-skin depth-good conductors

    I am desperate with an assignment and i would be grateful if someone could answer the following question. I read about skin effect and skin depth and i found the following one. "The skin effect depends upon the nature of material used for the conductor diameter of the wire, frequency, shape of...
  44. H

    How Does the Skin Effect Differ from Gamma Ray Penetration in Conductors?

    Skin Effect: . where = resistivity of the conductor = angular frequency of current = 2π × frequency = relative magnetic permeability of the conductor = the permeability of free space ------------------------------ From Wiki According to Skin Effect, the higher the frequency, the less...
  45. F

    Diffusion rate of oxygen through skin

    Homework Statement i) At rest a 70 kg person with an area of 1.7 m2 consumes around 14 litres of oxygen per hour. Around 2% of this is provided by diffusion through their skin. Calculate the diffusion rate for oxygen through human skin, in millilitres per second per square metre. ii) What...
  46. L

    How skin reduces impact force on bones

    I am very interest in knowing about how skin reduced force that can damage bone. I guess it act like a protective layer by flexing and stretching such as a trampoline. Also skin redistribute the force and spread out evenly and the soft tissue play role here too. Please help if someone have any...
  47. A

    What is the working principle of wire grid polarizers?

    Hello forum, I have a few doubts on EM. 1. The skin depth formula for constant current(DC) shows that there can be current uniformly distributed through the cross-section of a conductor.However as there can be no electric field within a conductor(as per Maxwell's equations) there can be no...
  48. M

    If water molecules are so smallwhy don't they go through skin pores?

    I read that essential oils can go through the skin. I am told that there are more water molecules in just 10 drops of water than stars in the whole universe, so if they are so tiny, why don't they go through the skin membrane pores, which are perfectly visible under an optical microscope? You...