Skin Maintains Structural Rigidity

Biological Strategy

Humans

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Protect From Excess Liquids

While water is essential to life, too much water or other liquids can overwhelm living systems. Excess liquids can, for example, decrease a living system’s access to oxygen, promote excessive bacterial or fungal growth, or strip away soil and nutrients. To prevent the accumulation of excess liquids, living systems must control the movement of liquids across their boundaries or surfaces. They do so using waterproofing materials or structures, slowing flow, and/or facilitating flow to move the liquid away. Plant leaves, for example, commonly have waxy surfaces comprised of water-repelling chemicals to keep water from engorging the leaves or facilitating bacterial and fungal growth.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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Human skin maintains its structural rigidity while expanding in water due to helical fibers of keratin woven into a three-dimensional pattern.

"’Our model provides an explanation as to why the skin maintains its structural rigidity and expansion in water, which was something that was never quite able to be explained,’ says [Myfanwy Evans of the Australian National University in Canberra]. Evans says the stratum corneum is made up of fibers of keratin that are woven together in a three-dimensional pattern. The researchers found the particular weave of the keratin enables it to act like a sponge, staying robust while absorbing water. The helical fibers also straighten out, allowing the material to expand and increase the volume of water it can hold, says Evans. But the key point is that as the material expands, all of the contacts between each of the fibers are maintained. ‘Contact between fibers are what gives the material structural stability,’ says Evans. ‘In this expansion all of those inter-fiber contacts are maintained so the material stays as a rigid material.’ Hence the remarkable properties of skin while we soak in the bath…[Evans] says the new understanding will make it easier for scientists to make materials that have this same property as skin." (Salleh 2011:1)

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