Created by CK-12 Foundation/Adapted by Christine Miller Show
Art for All ErasPictured in Figure 10.2.1, is Maud Stevens Wagner, a tattoo artist from 1907. Tattoos are not just a late 20th and early 21st century trend. They have been popular in many eras and cultures. Tattoos literally illustrate the biggest organ of the human body: the skin. The skin is very thin, but it covers a large area — about 2 m2 in adults. The skin is the major organ in the . What Is the Integumentary System?In addition to the skin, the includes the hair and nails, which are organs that grow out of the skin. Because the organs of the integumentary system are mostly external to the body, you may think of them as little more than accessories, like clothing or jewelry, but they serve vital physiological functions. They provide a protective covering for the body, sense the environment, and help the body maintain . The SkinThe is remarkable not only because it is the body’s largest organ: the average square inch of skin has 20 blood vessels, 650 sweat glands, and more than 1,000 nerve endings. Incredibly, it also has 60,000 pigment-producing cells. All of these structures are packed into a stack of cells that is just 2 mm thick. Although the skin is thin, it consists of two distinct layers: the epidermis and dermis, as shown in the diagram (Figure 10.2.2). Figure 10.2.2 The epidermis is the thinner outer layer of skin, and the dermis is the thicker inner layer of skin. The latter contains structures such as blood vessels and sweat glands.Outer Layer of SkinThe outer layer of skin is the . This layer is thinner than the inner layer (the dermis). The epidermis consists mainly of epithelial cells, called , which produce the tough, fibrous protein . The innermost cells of the epidermis are that divide continuously to form new cells. The newly formed cells move up through the epidermis toward the skin surface, while producing more and more keratin. The cells become filled with keratin and die by the time they reach the surface, where they form a protective, waterproof layer. As the dead cells are shed from the surface of the skin, they are replaced by other cells that move up from below. The epidermis also contains , the cells that produce the brown pigment melanin, which gives skin most of its colour. Although the epidermis contains some sensory receptor cells — called — it contains no nerves, blood vessels, or other structures. Inner Layer of SkinThe is the inner, thicker layer of skin. It consists mainly of tough , and is attached to the epidermis by collagen fibres. The dermis contains many structures (as shown in Figure 10.2.2), including blood vessels, sweat glands, and hair follicles, which are structures where hairs originate. In addition, the dermis contains many sensory receptors, nerves, and oil glands. Functions of the SkinThe skin has multiple roles in the body. Many of these roles are related to . The skin’s main functions are preventing water loss from the body and serving as a barrier to the entry of microorganisms. Another function of the skin is synthesizing vitamin D, which occurs when the skin is exposed to ultraviolet (UV) light. Melanin in the epidermis blocks some of the UV light and protects the dermis from its damaging effects. Another important function of the skin is helping to regulate body temperature. When the body is too warm, for example, the skin lowers body temperature by producing sweat, which cools the body when it evaporates. The skin also increases the amount of blood flowing near the body surface through vasodilation (widening of blood vessels), bringing heat from the body core to radiate out into the environment. The sweaty hair and flushed skin of the young man pictured in Figure 10.2.3 reflect these skin responses to overheating. Figure 10.2.3 Both sweating and flushing of the skin are signs that the skin is working to cool the body.Hair Figure 10.2.4 Eyelashes protect the eyes.is a fibre found only in mammals. It consists mainly of keratin-producing . Each hair grows out of a in the . By the time the hair reaches the surface, it consists mainly of dead cells filled with . Hair serves several homeostatic functions. Head hair is important in preventing heat loss from the head and protecting its skin from UV radiation. Hairs in the nose trap dust particles and microorganisms in the air, and prevent them from reaching the lungs. Hair all over the body provides sensory input when objects brush against it, or when it sways in moving air. Eyelashes and eyebrows (see Figure 10.2.4) protect the eyes from water, dirt, and other irritants. NailsFingernails and toenails consist of dead filled with . The keratin makes them hard but flexible, which is important for the functions they serve. prevent injury by forming protective plates over the ends of the fingers and toes. They also enhance sensation by acting as a counterforce to the sensitive fingertips when objects are handled. In addition, the fingernails can be used as tools. Interactions with Other Organ SystemsThe skin and other parts of the work with other organ systems to maintain .
The science of skin – Emma Bryce, TED-Ed, 2018. Why do we have to wear sunscreen? – Kevin P. Boyd, TED-Ed, 2013.
Scarification | National Geographic, 2008. AttributionsFigure 10.2.1 Maud_Stevens_Wagner -The Plaza Gallery, Los Angeles, 1907 from the Library of Congress on Wikimedia Commons is in the public domain (https://en.wikipedia.org/wiki/public_domain). Figure 10.2.2 Anatomy_The_Skin_-_NCI_Visuals_Online by Don Bliss (artist) from National Cancer Institute, on Wikimedia Commons is in the public domain (https://en.wikipedia.org/wiki/public_domain). Figure 10.2.3 shashank-shekhar-Db1J_qp_ctc [photo] by Shashank Shekhar on Unsplash is used under the Unsplash License (https://unsplash.com/license). Figure 10.2.4 Eyelashes by aryan-dhiman-93NBu0zG_H4 [photo] by Aryan Dhiman on Unsplash is used under the Unsplash License (https://unsplash.com/license). Reference National Geographic. (2008). Scarification | National Geographic. YouTube. https://www.youtube.com/watch?v=Lfhot7tQcWs&t=1s TED-Ed. (2018, March 12). The science of skin – Emma Bryce. YouTube. https://www.youtube.com/watch?v=OxPlCkTKhzY&feature=youtu.be TED-Ed. (2013, August 6). Why do we have to wear sunscreen? – Kevin P. Boyd. YouTube. https://www.youtube.com/watch?v=ZSJITdsTze0&feature=youtu.be How does the integumentary contribute to immunity?It retains body fluids and defends against the entry of invaders such as viruses, bacteria and parasites. It also helps to maintain a constant body temperature. Skin contains receptors that sense, for example, temperature, touch and pain.
How does the integumentary system work with the other body systems?The skin and other parts of the integumentary system work with other organ systems to maintain homeostasis. The skin works with the immune system to defend the body from pathogens by serving as a physical barrier to microorganisms. Vitamin D is needed by the digestive system to absorb calcium from food.
Which layer of the skin is part of the body's immune system?Protects your body: Langerhans cells in the epidermis are part of the body's immune system. They help fight off germs and infections. Provides skin color: The epidermis contains melanin, the pigment that gives skin its color.
How do the integumentary and lymphatic systems work together?The lymphatic system delivers lymph, white blood cells, and antibodies to the site of any infection the breaches the barrier of the integumentary system. Additionally, the lymphatic system helps to protect the integumentary system by pumping lymph through the skin of the integumentary system.
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