Definition of shell and skin

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Shell, has a lot of meaning and significance, including:
1. leather-hard pieces of skin eg coconuts;
2. parts of the coconut shell that hard to spot the water, being
3. which resembles the shell is the head;
Parts of the hollow shell where coconut shoots, bottom; manly parts of the upper parts of the shell shell which is located at the top if it's coconuts hanging stems.
head head bone that protects the contents of the head, especially the brain, cranium; skull; cranium; - knee bone behind the knee crease; pattela rotula; - fiddle fiddle parts that used to echo the sound, usually made ​​of shell. now discuss skin problems ,soft skin is the outer covering of vertebrates . Other animal coverings such as the arthropod exoskeleton has different developmental origin , structure and chemical composition .In mammals , the skin is the largest organ of the integumentary system made ​​up of multiple layers of ectodermal tissue , and keep the underlying muscles , bones , ligaments and internal organs .All mammals have some hair on their skin , even marine mammals which apparently hairy . Skin interface with the environment and is the first line of defense from external factors .For example , the skin plays an important role in protecting the body against pathogens and excessive water loss of other functions are insulation , temperature regulation , sensation , and the production of folate vitamin D.Severely damaged skin may heal by forming scar tissue . It is sometimes discolored and depigmented . Skin thickness also varies from location to location in the organism . In humans , for example , located under the skin around the eyes and eyelids are 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 " crow's feet " and wrinkles . The skin on the palms and soles of the feet is 4 mm thick and thick skin in the body . The speed and quality of wound healing in the skin promoted by the acceptance of estrogen .Fur is dense hair . Especially , insulating fur adds leather supply but can also serve as a secondary sexual characteristic or as camouflage . In some animals , the skin is very hard and thick , and can be processed to create leather . Reptiles and fish have hard protective scales on their skin for protection , and birds have hard feathers , all made ​​of tough β - keratin . Amphibian skin is not a strong barrier to passage of chemicals and is often subject to osmosis and diffusion strength . For example , a frog sitting in the anesthetic solution will quickly sedated , because the chemical diffuses through the skin . 
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