: How and why does the hairs on your body stand during different conditions?

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: How and why does the hairs on your body stand during different conditions?

In: Biology

The skin is not a perfectly smooth, continuous surface even though it may look like it. When you look very closely, you’ll notice little dots called pores. Skin pores are linked to sweat glands under the skin, which are parts of your skin that produce sweat (which contains water) and release it onto your skin. Once on the skin, the sweat evaporates into the air, giving a cooling effect for your skin.

Now water is also used in the body in reactions that generate heat, which are important in keeping you warm when it’s cold outside. So you don’t want to lose any water when you’re cold.

In parts of the body where hair grows, some of the pores have hair coming out of them. These hairs usually lie flat (on your arm for example) but stand up when it’s cold. This closes off the skin pores, preventing water from being lost as sweat, meaning that you have more water to use to generate heat (and no water is used to keep you cool by sweating).

Hairs also stand up when you’re scared or get goosebumps. What these 3 have in common is that they all cause you to shiver, which causes blood vessels to become temporarily narrower to reduce the heat lost from blood.

The way the hairs stand up is that they are attached to these small muscles next to the sweat glands, called “arrector pili” muscles. These will contract in response to shivering and cause the hairs to stand up.