We use them every day, but have you ever thought that your lips don’t look, feel or act like other parts of your body? Why are they so red, so delicate, and so prone to drought? And why did humans evolve to have lips when other creatures—birds and turtles, for example—get along just fine without them?
“Lips are fundamental to eating, breathing and speech,” says Noël Cameron, professor of humanities biology at Loughborough University in the UK, Live Science said in an email.
Lips, Cameron noted, are sensitive. According to the Jamaica Hospital (opens in new tab)Lips contain around 1 million nerve endings, which is why they are so strongly affected by touch and changes in temperature and humidity.
“The skin of the lip forms the boundary between the outer skin of the face and the inner lining of the inside of the mouth,” Cameron said. “The mucosa is represented by a large area in the sensory cortex Brain and is therefore highly sensitive.”
Cameron found that because of this, the lips are capable of fine and gross muscular movement.
Related: Can Lip Balm Make Your Chapped Lips Worse?
This ability for delicate and precise movements—provided by five muscles for lip-lifting (upward motion) and four for lip-lifting (downward motion)—enables people to communicate in the ways we do.
Lips are critical to “bilabial and labiodental consonant sounds, as well as vowel rounding,” Cameron said.
Bilabial sounds can only be produced using both lips (the letter “p” in Picnic, for example), while labiodental sounds require the use of both lips and teeth (the letter “f” in fructose).
Without using or moving your lips, Cameron added, it’s incredibly difficult to make some sounds or pronounce certain letters: For example, try vocalizing the letters M, W, or B without using your lips to get an idea to get out of the difficulties you face ventriloquist.
red in the face
But why lips see how you do it? Why are they so red, especially compared to other parts of the face?
“The skin of the lip is very thin, at three to five layers of cells, compared to typical facial skin, which has up to 16 layers,” Cameron said. “With light skin color, the lip skin contains fewer melanocytes (cells which produce melanin pigments that give skin its color). For this reason the blood vessels appear through the skin of the lips, resulting in their striking red hue.”
Cameron added that the effect is less pronounced on darker skin tones because “the skin on the lips contains more melanin and is therefore optically darker.”
There are also other differences between the lips and other parts of the human face, Cameron pointed out.
“Lip skin is very thin, not hairy and has no sweat glands. Therefore, it is relatively fragile, feels dry and tears easily. It doesn’t have the usual protective layer of sweat and body oils that keep skin smooth, inhibit pathogens and regulate heat. As a result, the lips dry out more quickly and become chapped more easily.”
Lips, like the soles of the feet and the palms of the hands, do not have hair follicles, so hair cannot grow there. This is because these body parts are more effective without hair – it would be much more difficult to grasp objects if our palms were hairy, while our lips would be less capable of clear speech if hair-encumbered.
A moment on your lips
Of course, while lips are essential for speaking and eating, they are also commonly used for kissing. “They act as an erogenous zone and as a point of attraction,” Cameron said.
In a 2010 research published in the journal perception (opens in new tab), white participants could adjust the color and contrast of lips in photos to enhance certain qualities. Researchers found that participants were more likely to increase lip redness to improve the femininity and attractiveness of women’s faces. Despite this, there are mixed opinions in research that the color “red” (or red lips) is a sign of sexual attractiveness.
Originally published on Live Science.
https://www.livescience.com/32193-why-are-lips-red.html Why are human lips red?