93 10.1 Case Study: Skin, Hair, and Nails – Decorative but Functional
Created by CK-12 Foundation/Adapted by Christine Miller
Case Study: Wearing His Heart on His Sleeve
Aiko, 22, and Larissa, 23, met through mutual friends and hit it off right away. They began dating and just four months later, they are now madly in love. They spend as much time as they can with each other, and have decided to move in together when Larissa’s roommate moves out. They are even discussing getting married one day.
Inspired by his passion for Larissa, Aiko is considering getting her name tattooed on his arm. As you probably know, tattoos are designs on the skin created by injecting pigments into the skin with a needle. Aiko looks up different tattoo styles online, and starts to envision what he would want in a tattoo.
One day at a street festival, Aiko sees a sign that says “Henna Tattoos.” Henna tattoos are not technically tattoos — they are temporary designs that artists can create on the skin using a paste made out of the leaves of the henna plant. The henna stains the skin a reddish-brown colour, and once the paste is scraped off, the design typically remains on the skin for a few weeks. The use of henna to create designs on the skin is called mehndi. It is traditionally used by people in and from regions such as India, Pakistan, the Middle East, and Africa to celebrate special occasions, particularly weddings. Mendhi is often done on the palms of the hands and soles of the feet, where the designs usually come out darker than on other areas of the skin. You can see some examples of henna art in the images below.
Figure 10.1.2 Examples of henna art.
Aiko asks the mehndi artist to inscribe Larissa’s name on his arm, so that he can see whether he likes it without making the permanent commitment of a real tattoo. Two days later, Aiko visits his parents. They are not familiar with mehndi, and they have a moment of panic when they think he got a real tattoo. Aiko reassures them that it is temporary, but tells them that he is thinking about getting a real tattoo.
His parents are concerned. His father points out that he has not known Larissa long — what if they break up and he regrets the tattoo? His mother additionally worries about whether tattoos are safe. Aiko says that he doesn’t think he will regret the decision, but if he does, he can cover it up with another tattoo or get it removed with laser treatments. He also tells them that he would go to an artist and shop that are reputable, and take appropriate safety precautions. His parents warn him that getting a tattoo removed may not be as simple as he thinks, and that he should think very carefully before making such a permanent decision.
Humans have long decorated and adorned their skin with tattoos, makeup, and piercings. They also colour, cut, straighten, curl, and remove their hair; and paint, grow, and cut their nails. The skin, hair, and nails make up the integumentary system. As you read this chapter, you will learn about the important biological functions that these organs carry out, beyond being a convenient canvas for personal expression. At the end of the chapter you will find out if Aiko got his tattoo. You will also learn more about how tattoos, mehndi, and laser tattoo removal work, as well as the important considerations to protect your health if you are thinking about getting a tattoo.
In this chapter you will learn about the structure and functions of the integumentary system, along with its relationships to culture, evolution, and health. Specifically, you will learn about:
- The functions of the organs of the integumentary system — the skin, hair, and nails — including protecting the body, helping to regulate homeostasis, and sensing and interacting with the external world.
- The two main layers of the skin: the thinner outer layer (called the epidermis) and the thicker inner layer (called the dermis).
- The cells and layers of the epidermis and their functions, including synthesizing vitamin D and protecting the body against injury, pathogens, UV light exposure, and water loss.
- The composition of epidermal cells and how the epidermis grows.
- The composition and layers of the dermis and their functions, including cushioning other tissues, regulating body temperature, sensing the environment, and excreting wastes.
- The specialized structures in the dermis, which include sweat and sebaceous (oil) glands, hair follicles, and sensory receptors that detect touch, temperature, and pain.
- The structure and biological functions of hair, which include retaining body heat, detecting sensory stimuli, and protecting the body against UV light, pathogens, and small particles.
- How hair grows, how variations in hair colour and texture arise, and hypotheses about the evolution of hair in humans.
- The sociocultural roles of hair, including its expression of characteristics like sex and age, as well as cultural identity and social cues.
- The structure and functions of nails, which includes protecting the fingers and toes, enhancing the detection of sensory stimuli, and acting as tools.
- How nails grow and how they can reflect and affect our health.
- Skin cancer — which is the most common form of cancer — and its types and risk factors.
As you read the chapter and learn more about the skin, think about the following questions:
- Why do you think real tattoos are permanent, but mehndi is not?
- Why do you think mehndi might come out darker on the palms of the hands and soles of the feet than on other areas of the skin?
- What do you think are some of the health concerns about tattoos?
- Henna for hair by Andrey “A.I.” Sitnik ( www.sitnik.ru ) on Wikimedia Commons is released into the public domain (https://en.wikipedia.org/wiki/Public_domain).
- Henna on foot in Morocco by Bjørn Christian Tørrissen on Wikimedia Commons is used under a CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/deed.en) license.
- Mehndi (front) by AKS.9955 on Wikimedia Commons is used under a CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/deed.en) license.
- Tags: Hand Jewelry Ornaments. . .Henna by BenBernardBags on Pixabay is used under the Pixabay License (https://pixabay.com/ja/service/license/).