Do you ever feel like you have to shave the hair on your legs more frequently in the summer than you do in the winter? If so, it’s not all in your imagination! Believe it or not, hair all over your body grows a bit faster in the summer than it does in the winter. In fact, while we’re on the topic of hair’s growth, you might be interested to know that hair also grows faster during the day than it does at night. How is this all this possible? Our hair has muscles!
It may seem crazy to think, but it’s true, your hair has muscles! As many of you already know, your skin is the largest organ of your body. Not only does it make a good canvas for all the makeup and beauty trends we test out, but it also works to protect your body’s complex system of bones, muscles, tissue, nerves, blood vesicles and more. What you may not have previously known is that both hair and nails are actually modified forms of skin. In fact, hair grows just about everywhere on the body with the exception of three areas – can you guess where hair doesn’t grow? If you guessed the palms of the hands, soles of the feet, and lips, then you’re correct.
Arrector Pili Muscle
The what?! You’re probably asking yourself. Remember how at the beginning of the article we told you that your hair has muscles? Well, being that there are about 320 different types of muscles in the human body, scientist figured it would be easier to identify them by giving each one a name – makes sense. Anyways, “arrector pili” is the name given to the muscles of the hair. Of course, your strands aren’t exactly weightlifting all day, but the arrector pili are getting quite the workout. The muscle isn’t on the part of the strand that you style, it’s actually attached to the root of the hair follicle under the skin. When the muscle contracts you’ll see goose bumps (this is why we never get goosebumps on the soles of our feet, palms of our hands, or lips – because there’s no hair there, remember!?).
If you’re confused as to why the muscle contracts on its own to create goosebumps, that’s okay, we’re going to clear it all up for you right now. As explained above, the arrector pili are attached to the hair follicle, but it’s not just a single unit. Rather the muscle is made up of tons of smooth muscle fibers which create it follicular muscle unit. This unit branches out to attach itself to numerous hair follicles. Unlike your biceps and triceps which rely on the cerebrum to send a signal to the peripheral nervous system telling the muscles when to flex and relax, the arrector pili are controlled by the sympathetic branch of the autonomic nervous system. This means that the contraction of the muscle is involuntary, and it typically stimulated by external sensations (such as a cool breeze) and internal emotions (such as fear). When you experience a certain sensation or emotion, the sympathetic nervous system is being stimulated and causing the muscles to contract, thus giving you goosebumps.