What is Skin?
{{about|skin on its own|the skin along with its hair, nails, and related things|Integumentary system}} [[Image:Human skin structure.jpg|thumb|200px|Close view of the ''skin'' on a human hand.]] '''Skin''' is the [[outside]] covering of [[mammals]] and some other animals. It has many purposes. First of all, it is a defense against the entry of [[pathogens]] such as [[bacteria]] and [[Parasitism|parasites]]. Second, it regulates (keeps in control) the body's temperature. It allows [[evaporation]] from its surface, and adjusts it. It is a physical defense, very strong in some animals, but rather weak in humans. The skin and hair on mammals has several purposes. In addition to [[temperature regulation]] and defense, some hair is used for signaling. Most animals add other defenses to their skin. [[Mammal|Mammals]] have [[hair]] or [[fur]] on their skin. [[Bird]]s have [[feather]]s on their skin. Most [[fish]], and [[reptile]]s, like [[snake]]s and [[lizard]]s, have [[Scale (zoology)|scales]] on their skin.<ref>{{Cite web|title=Skin: Layers, Structure and Function|url=https://my.clevelandclinic.org/health/articles/10978-skin|access-date=2021-11-11|website=Cleveland Clinic}}</ref> [[Humans]] can have different skin colours like [[black people]] and [[white people]] depending on their race and has to do with [[genetics]]. The skin is actually the largest [[organ]] of the human body. Without skin, humans would easily get infected with diseases. Skin helps regulate [[body temperature]]. Skin lowers the potentially harmful effects of [[Ultraviolet|UV rays]]. As part of the [[immune system]], skin can help warn people to certain diseases.<ref>{{Cite web|last=Team|first=Gundry MD|date=2021-11-04|title=What is healthy skin and how do you achieve it?|url=https://gundrymd.com/healthy-skin/|access-date=2021-11-11|website=Gundry MD|language=en-US}}</ref> Clean skin is important to health, and all mammals groom their hair and skin. [[Skin care]] is much work. Skins can be made into [[leather]]. Leather is sometimes used to