We use them every day, but have you ever wondered if your lips don’t look, feel or act like other parts of your body? Why are they so red, so sensitive and so prone to dryness? And why did humans evolve to have lips, while other creatures—birds and turtles, for example—get by just fine without them?
“Lips are indispensable for eating, breathing and speaking,” says Noel Cameron, professor of human biology at Loughborough University in the UK.
The lips are, the teacher adds, very sensitive. According to the Jamaica Hospital, the lips contain approximately one million nerve endings, which are affected by touch as well as changes in temperature and humidity.
What is the role of the lips?
“The skin of the lip forms the boundary between the outer skin of the face and the inner mucous membrane of the inside of the mouth,” Cameron said. “The mucous membrane is a large area in the sensory cortex of the brain and is therefore very sensitive.” Cameron noted that because of this, the lips are capable of fine and gross muscle movements, respectively Live Science.
The ability to perform delicate and precise movements—provided by five muscles for raising the lips, moving up, and four for depressing the lips, moving down—allows people to communicate in the specific way. The lips are vital for “bilabial and labiodental consonant sounds, as well as vowel rounding,” Cameron said. Bilabial sounds can only be made using both lips – the letter “p” in picnic, for example, while labiodental sounds require the use of lips and teeth – the letter “f” in fructose.
Without using or moving your lips, Cameron added, it’s incredibly difficult to make certain sounds or pronounce certain letters. Try vocalizing the letters M, W or B without using your lips, for example, to get an idea of the difficulties a ventriloquist faces.
Red color spot
But why do lips look the way they do? Why are they so red, especially compared to other parts of the face? “The skin of the lip, with three to five cell layers, is very thin compared to typical facial skin, which has up to 16 layers,” Cameron said. “With a light skin color, the skin of the lips contains fewer melanocytes – cells that produce the pigment melanin, which gives the skin its color. Because of this, blood vessels appear through the skin of the lips, which leads to their noticeable red coloration.”
Cameron added that with darker skin color, the effect is less prominent because “the skin of the lips contains more melanin and is thus visually darker.” There are other differences between the lips and other parts of the human face, Cameron pointed out. The skin on the lips is very thin, not hairy and has no sweat glands. Therefore, it is relatively fragile, dry to the touch and easily detached.
It lacks the usual protective layer of sweat and body oils that keep skin smooth, inhibit pathogens and regulate heat. As a result, lips dry out faster and become chapped more easily. The lips, like the soles and palms, have no hair follicles, so hair cannot grow there. This is because these body parts are more efficient without hair – it would be much more difficult to grasp objects if our palms were hairy, while our lips would be less able to speak clearly if they were adorned with hair .
An introspection on lips
Of course, while vital for speaking and eating, lips are also frequently used for kissing. “It acts as an erogenous zone and as an attraction zone,” Cameron said.
In research published in 2010 in the journal Perceptionwhite participants could adjust the color and contrast of lips in photographs to enhance certain qualities.
The researchers found that participants were more likely to increase the redness of the lips to enhance the femininity and attractiveness of women’s faces. Even so, research boils down to the idea that “red” or red lips are a sign of sexual attractiveness.