Personally, I'm most grateful for having skin all over my body. Skin has so many functions, I don't even think I could name them all. I mean, just take a few moments, and think about what it would be like to not have skin.
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Have you thought about it? Without skin, you would just be a huge, throbbing muscle mass that doesn't even look human. You'd be in great pain all the time. Can you imagine standing out in the desert heat with no skin? Bacon, anyone?
You'd look like something from Resident Evil. Also, without skin, you wouldn't be able to keep cool or warm. When you're cold, you get goose bumps, which helps create insulation. And when you're hot, your skin excretes sweat that evaporates and keeps you cool! Skin also protects us from the sun (to an extent) and prevents water loss.
Not to mention, without skin, you wouldn't be able to feel anything. Our skin contains the nerves which make up our sense of touch and ability to feel cold and heat. Skin is also vital to the way we look; it's what makes you look like you! Everyone has a different appearance, all thanks to the wonderful thing that is skin.