173 Chapter 10 Answers: Integumentary System

10.2 Introduction to the Integumentary System: Review Questions and Answers

1. Name the organs of the integumentary system. The organs of the integumentary system are the skin, hair, and nails.
2. Compare and contrast the epidermis and dermis. The epidermis and dermis are the two distinct layers of the skin. The epidermis is the thinner outer layer of the skin, and the dermis is the thicker inner layer of the skin. The epidermis consists mainly of epithelial cells called keratinocytes, whereas the dermis consists mainly of connective tissues. The dermis also contains such structures as blood vessels, nerves, hair follicles, and sweat and oil glands. The epidermis, in contrast, does not contain any of these structures with the exception of sensory receptor cells called Merkel cells.
3. Identify functions of the skin. Functions of the skin include preventing water loss from the body, serving as a barrier to the entry of microorganisms, synthesizing vitamin D, blocking UV light, and helping to regulate body temperature.
4. Self-marking
5. What is the composition of hair? Hair is composed mainly of dead keratinocytes that are filled with keratin.
6. Describe three physiological roles played by hair. Answers may vary. Sample answer: Three physiological roles played by hair are reducing heat loss from the head, filtering particles out of inhaled air in the nose, and keeping harmful substances out of the eyes.
7. What do nails consist of? Nails consist mainly of keratin-filled, dead keratinocytes.
8. List two functions of nails. Answers may vary. Sample answer: Two functions of the nails are enhancing the sense of touch in the fingertips and protecting the ends of the fingers and toes.
9. In terms of composition, what do the outermost surface of the skin, the nails, and hair have in common? Answers may vary. Sample answer: The outermost surface of the skin, and the nails and hair are all mainly composed of dead cells called keratinocytes that are filled with keratin.
10. Identify two types of cells found in the epidermis of the skin. Describe their functions. Answers may vary. Sample answer: Keratinocytes are found in the epidermis and produce keratin to provide a waterproof, protective layer. Melanocytes are another type of cell in the epidermis and they produce melanin, which protects the dermis from UV radiation.
11. Which structure and layer of skin does hair grow out of? Hair grows out of follicles in the dermis.
12. Identify three main functions of the integumentary system. Give an example of each. Answers may vary. Sample answer: Three main functions of the integumentary system are to protect the body, sense the environment, and help maintain homeostasis. For example, the skin helps protect the body from pathogens; nails help enhance sensation by providing counterforce; and hair helps to maintain body temperature by preventing heat loss from the head.
13. What are two ways in which the integumentary system protects the body against UV radiation? Two ways that the integumentary system protects the body against UV radiation are melanin in the epidermis and hair on the head ­— both of which block the damaging effects of UV light.

10.3 Epidermis: Review Questions and Answers

1. What is the epidermis? The epidermis is the outer and thinner of the two main layers of the skin, the other layer being the dermis.
2. Identify the types of cells in the epidermis. Types of cells in the epidermis include epithelial cells called keratinocytes that produce keratin; melanocytes that produce the brown pigment melanin; immune cells called Langerhans cells that fight pathogens; and Merkel cells that respond to light touch.
3. Describe the layers of the epidermis. The innermost layer of the epidermis is the stratum basale, which contains basal cells and melanocytes. The next layer is the stratum spinosum, which is the thickest of the layers and contains Langerhans cells as well as spiny keratinocytes. The layer after that is the stratum granulosum, in which cells are nearly filled with keratin and starting to die. The stratum lucidum occurs next, but only on the palms of the hands and soles of the feet. It consists of stacks of translucent dead keratinocytes. The outermost layer of the epidermis is the stratum corneum, which consists of flat, dead, tightly packed keratinocytes.
4. Self-marking
5. State one function of each of the four epidermal layers found all over the body. Answers may vary. Sample answer: One function of the stratum basale is producing new keratinocytes by the division of basal stem cells. One function of the stratum spinosum is fighting infections with Langerhans cells. One function of the stratum granulosum is releasing lipids to form a lipid barrier in the epidermis. One function of the stratum corneum is to provide a tough protective barrier for underlying layers of the skin.
6. Explain three ways the epidermis protects the body. Answers may vary. Sample answer: Three ways the epidermis protects the body is by preventing physical damage, keeping out pathogens, and absorbing UV light so it cannot damage skin cells.
7. What makes the skin waterproof? The skin is waterproof because of lipids produced in the epidermis and because of tightly packed, keratin-filled epidermal cells in the stratum corneum.
8. Why is the selective permeability of the epidermis both a benefit and a risk? The selective permeability of the epidermis is a benefit because it allows the absorption of medications via topical ointments and skin patches. The selective permeability of the epidermis is a risk because it allows certain harmful substances such as lead to be absorbed through the epidermis.
9. How is vitamin D synthesized in the epidermis? Vitamin D is synthesized in the epidermis when UV light strikes vitamin D precursor molecules called 7-dehydrocholesterol and changes them to vitamin D3. The vitamin D3 is converted in the kidneys to calcitriol, which is the biologically active form of vitamin D.
10. Identify three pigments that impart colour to skin. The main pigment that imparts colour to the skin is melanin, the dark brown pigment produced by melanocytes in the stratum basale. In skin with low levels of melanin, two other pigments are also important. They include the pigment carotene that gives skin a yellowish tint and the pigment hemoglobin in blood vessels in the dermis that gives skin a pinkish tint.
11. Describe bacteria that normally reside on the skin, and explain why they do not usually cause infections. The surface of the human skin normally provides a home to countless numbers of bacteria belonging to about 1,000 bacterial species from 19 phyla. The concentrations and types of bacteria on the skin differ from one part of the body to another depending on the environment provided by the skin (such as oily or dry). The bacteria living on the skin do not usually cause infections because they keep each other in check so there is a healthy balance of microorganisms.
12. Explain why the keratinocytes at the surface of the epidermis are dead, while keratinocytes located deeper in the epidermis are still alive. Answers may vary. Sample answer: Keratinocytes are born in the deepest layer of the epidermis and then are pushed outwards as new keratinocytes are born. The blood vessels in the skin are located in the dermis, below the epidermis. Therefore, as the keratinocytes get pushed further away from the blood vessels and towards the outer surface of the skin, they begin to die because they can’t get needed substances from the blood.
13. Which layer of the epidermis contains keratinocytes that have begun to die? Stratum granulosum.
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15. Explain why our skin is not permanently damaged if we rub off some of the surface layer by using a rough washcloth. Answers may vary. Sample answer: New cells are continually being produced in the stratum basale of the epidermis and being pushed up towards the surface of the skin. So if we rub off some of the dead surface cells, new cells are there to replace them. Dead cells from the stratum corneum are continually being shed and replaced anyway — this is a normal process.

10.4 Dermis: Review Questions and Answers

1. What is the dermis? The dermis is the inner of the two major layers that make up the skin.
2. Describe the basic anatomy of the dermis. The basic anatomy of the dermis is a matrix composed of connective tissues, including collagen fibres, which provide toughness, and elastin fibres, which provide elasticity. A gel-like protein substance surrounds the fibres. Virtually all skin structures such as sensory receptors, blood vessels, and glands are also located in the dermis.
3. Compare and contrast the papillary and reticular layers of the dermis. The papillary layer is the upper and thinner layer of the dermis, whereas the reticular layer is the lower and thicker layer of the dermis. The papillary layer is composed of loosely arranged collagen fibres, whereas the reticular layer is composed of densely woven collagen fibres. The papillary layer has papillae extending upward toward the epidermis; the reticular layer lacks such papillae. Both layers contain sensory receptors and blood vessels, but other skin structures, including hair follicles and glands, are located only in the reticular layer.
4. What causes epidermal ridges, and why can they be used to identify individuals? Epidermal ridges are caused by the papillae of the papillary layer of the dermis in the palms of the hand and soles of the feet. Epidermal ridges can be used to identify individuals because their patterns are genetically determined so no two people (other than identical twins) have exactly the same epidermal ridge pattern.
5. Name the two types of sweat glands in the dermis, and explain how they differ. The two types of sweat glands in the dermis are eccrine glands and apocrine glands. Eccrine glands occur all over the body and have ducts that empty through pores onto the skin surface. Apocrine glands occur only in the armpits and groin and have ducts that empty into hair follicles. Apocrine sweat then travels to the skin surface on the shafts of hairs. Eccrine sweat functions to cool the body. Apocrine sweat is an oily substance produced only after puberty. When bacteria digest apocrine sweat, it causes body odor.
6. What is the function of sebaceous glands? The function of sebaceous glands is to produce the thick, oily substance called sebum, which waterproofs the hair and skin and helps prevent them from drying out.
7. Describe the structures associated with hair follicles. Structures associated with hair follicles include capillaries and nerve endings. Each hair follicle also has a sebaceous gland that secretes sebum into the follicle and a tiny arrector pili muscle that moves the follicle and causes the hair to stand up when it contracts.
8. Explain how the dermis helps regulate body temperature. When body temperature rises, sweat glands in the dermis secrete sweat. As the sweat evaporates, it cools the body. Blood vessels in the dermis also dilate, which brings more heat to the surface, where it can radiate into the environment. When body temperature falls, sweat glands stop producing sweat, and blood vessels in the skin constrict, thus conserving body heat. The arrector pili muscles also contract, raising hairs that trap insulating air near the surface.
9. Identify three specific kinds of tactile receptors in the dermis, along with the type of stimuli they sense. Answers may vary. Sample answer: Three specific types of tactile receptors in the dermis are Meissner’s corpuscles, which sense light touch; Pacinian corpuscles, which sense pressure and vibration; and Ruffini corpuscles, which sense stretching and sustained pressure.
10. How does the dermis excrete wastes? What waste products does it excrete? The dermis excretes wastes in sweat. It excretes excess water and electrolytes and also certain metabolic wastes such as urea.
11. What are subcutaneous tissues? Which layer of the dermis provides cushioning for subcutaneous tissues? Why does this layer provide most of the cushioning, instead of the other layer? Answers may vary. Sample answer: Tissues that are below the skin.  The reticular layer of the dermis provides cushioning for subcutaneous tissues because it is thicker and composed of densely woven collagen and elastin fibres. The papillary layer of the dermis is thinner and is composed of more loosely arranged collagen fibres, so it can’t provide as much cushioning for the tissues below.
12. For each of the functions listed below, describe which structure within the dermis carries it out.
    1. Brings nutrients to and removes wastes from dermal and lower epidermal cells – Blood vessels
    2. Causes hairs to move – Arrector pili muscles
    3. Detects painful stimuli on the skin – Free nerve endings

10.5 Hair: Review Questions and Answers

1. Compare and contrast the hair root and hair shaft. The hair root is the part of the hair that is inside the hair follicle, whereas the hair shaft is the part of the hair that is outside the hair follicle and above the surface of the skin. The only living part of a hair is the hair root. The hair shaft consists of dead cells.
2. Describe hair follicles. Hair follicles are structures in the dermis containing stem cells that can keep dividing and allow hair to grow. Hair follicles have sebaceous glands that produce sebum, which lubricates and waterproofs hair. Hair follicles also have tiny arrector pili muscles that make hairs stand up when they contract.
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5. Explain variation in human hair colour. Hair colour is due to the presence or absence of two different forms of the pigment melanin: eumelanin and pheomelanin. Eumelanin is the dominant pigment in brown hair and black hair, and pheomelanin is the dominant pigment in red hair. Blond hair is the result of having only a small amount of melanin. Gray and white hair occur when melanin production slows down and eventually stops.
6. What factors determine the texture of hair? Factors that determine the texture of hair include curl pattern (due, in turn, to the shape of the hair follicle and hair shaft), thickness (which depends on follicle size), and consistency (the result of follicle volume and how open the cuticle is).
7. Describe two functions of human hair. Answers may vary. Sample answer: One function of human head hair is to help the body retain heat and protect the skin on the head from UV light. A function of hair all over the body is to enhance the sense of touch.
8. What hypotheses have been proposed for the loss of body hair during human evolution? One hypothesis for the loss of body hair during human evolution is that it would have made sweating more efficient for cooling the body because sweat evaporates more quickly from less hairy skin. Another hypothesis is that it would have led to fewer parasites on the skin, which might have been especially important when humans started living together in larger, more crowded social groups.
9. Discuss the social and cultural significance of human hair. The social significance of hair includes its roles as indicators of biological sex, age, and ethnicity. For example, males tend to have more body hair than females, and facial hair is a notable secondary male sex characteristic. White hair is a sign of older age, and hair colour and texture can be a sign of ethnic ancestry. Culturally, hairstyle may be an indicator of social group membership. Many religious practices also involve the hair. For example, Sikh men grow their hair long and cover it with a turban.
10. Describe one way in which hair can be used as a method of communication in humans. Answers may vary. Sample answer: Humans can use the position of their eyebrows to communicate nonverbally to each other.
11. Explain why waxing or tweezing body hair — which typically removes hair down to the root — generally keeps the skin hair-free for a longer period of time than shaving, which cuts hair off at the surface of the skin. Answers may vary. Sample answer: When you remove a hair down to the root, it will take a longer time for a new hair to grow back through the dermis and epidermis and out to the surface of the skin, compared to shaving where the cut tip remains right at the surface of the skin.

10.6 Nails: Review Questions and Answers

1. What are nails? Nails are accessory organs of the skin made of sheets of dead keratinocytes. They are on the distal ends of the digits.
2. Self-marking
3. Explain why most of the nail plate looks pink. Most of the nail plate looks pink because the pink colour of the underlying nail bed shows through the nail. The nail bed is pink because its dermal layer contains capillaries.
4. Describe a lunula. A lunula is a whitish crescent shape that shows through the nail plate at the proximal end of a nail. This is where a small amount of the nail matrix is visible under the nail plate.
5. Explain how a nail grows. A nail grows from a deep layer of living epidermal tissues, called the nail matrix, at the proximal end of the nail. Stem cells in the nail matrix keep dividing to allow nail growth, forming first the nail root and then the nail plate as the nail continues to grow longer and becomes visible.
6. Identify three functions of nails. Answers may vary. Sample answer: Three functions of nails are protecting the ends of the digits, enhancing sensations and precise movements in the fingertips, and acting as tools.
7. Give several examples of how nails are related to health. Answers may vary. Sample answer: Several examples of how nails are related to health are: the colour of the nail bed can be used to quickly assess a patient’s oxygen and blood flow; how the nail plate grows out can reflect recent health problems; and nails can absorb several harmful substances that can cause health problems.
8. What is the cuticle of the nail composed of? What is the function of the cuticle? Why is it a bad idea to cut the cuticle during a manicure? The cuticle of the nail is composed of dead epithelial cells. The function of the cuticle is to seal the edge of the nail to prevent infection. Cutting the cuticle can create breaks in the skin that allow infectious agents to enter.
9. Is the nail plate composed of living or dead cells? Dead cells.

10.7 Skin Cancer: Review Questions and Answers

1. What is skin cancer? Skin cancer is a disease in which skin cells grow out of control due to DNA damage. It begins in the epidermis of the skin.
2. How common is skin cancer? Skin cancer is more common than all other cancers combined. One in five Americans develops skin cancer in his or her lifetime.
3. Self-marking
4. Compare and contrast the three common types of skin cancer. The three common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.
5. Identify factors that increase the risk of skin cancer. Factors that increase the risk of skin cancer include first and foremost exposure to UV light. The increase in cancer risk due to UV light is especially great in people who have had blistering sunburns at a young age. Besides UV light exposure, other risk factors for skin cancer include having light coloured skin, having many moles, being diagnosed with precancerous skin lesions, having a family history of skin cancer, having a personal history of skin cancer, having a weakened immune system, and being exposed to other forms of radiation or to certain toxic substances.
6. How does exposure to UV light cause skin cancer? UV light damages DNA in the skin, and damaged DNA can result in cancer.
7. In which layer of the skin does skin cancer normally start? The epidermis.
8. Which two skin cancers described in this section start in the same sub-layer? Include the name of the sub-layer and the cells affected in each of these cancers. Basal cell carcinoma and melanoma both start in the stratum basale layer of the epidermis. Basal cell carcinoma occurs in the basal cells and melanoma starts in the melanocytes.
9. Which type of skin cancer is most likely to spread to other organs? Explain your answer. Melanoma, because the other types are unlikely to spread, or metastasize.
10. Which form of skin cancer is the most deadly? Melanoma.
11. What are some ways people can reduce their risk of getting skin cancer? Explain your answer. Answers may vary. Sample answer: Since UV radiation causes the vast majority of cases of skin cancer, the risk of skin cancer can be reduced by avoiding exposure to UV light. This can be done by using sunblock or sunscreen, staying in the shade, and wearing protective clothing. Also, children and teenagers should be particularly protected from the sun since having blistering sunburns early in life greatly increases the risk of skin cancer.

10.8 Case Study Conclusion and Chapter 12 Summary Review Questions and Answers

1. Describe one way in which the integumentary system works with another organ system to carry out a particular function. Answers will vary. Sample answer: The skin of the integumentary system works with the cardiovascular system to help regulate body temperature through vasoconstriction or vasodilation of blood vessels in the dermis.
2. Self-marking
3. Describe two types of waterproofing used in the integumentary system. Include the types of molecules and where they are located. Answers will vary. Sample answer: The stratum corneum, the uppermost layer of the epidermis, is made of tightly packed, dead keratinocytes that are filled with keratin. This provides a waterproof barrier for the skin. Oily sebum produced by the sebaceous glands at the hair follicles helps to waterproof the hair.
4. Explain why nails enhance touch sensations. Nails enhance touch sensations because they are hard and provide counterpressure to the tips of the digits. Therefore, this enhances the detection of touch sensations by the sensory receptors in the skin.
5. Why do you think light coloured skin is a risk factor for skin cancer? Answers may vary. Sample answer: Light coloured skin is a risk factor for skin cancer because it contains less melanin that darker skin. Melanin protects the skin from UV radiation, and UV radiation can cause cancer. Therefore, people with lighter skin are at more risk of getting skin cancer.
6. Describe the similarities between how the epidermis, hair, and nails all grow. Answers may vary. Sample answer: The epidermis, hair, and nails all grow through the division of stem cells that produce keratinocytes. The new cells are born at the base of the structure (the stratum basale; base of the hair follicle; and nail matrix, respectively) and push the older cells out.
7. What does the whitish crescent-shaped area at the base of your nails (toward your hands) represent? What is its function? The whitish crescent-shaped area at the base of our nails is called the lunula and consists of the part of the nail matrix that shows through the nail plate. The nail matrix contains blood vessels and nerves as well as stem cells that divide to produce keratinocytes, which make up the nail. Division of these cells allows nail growth.
8. What is one difference between human hair and the hair of non-human primates? Answers may vary. Sample answer: Humans have much less body hair than non-human primates.
9. Describe the relationship between skin and hair. Answers may vary. Sample answer: Hair originates from hair follicles, which are found in the dermis of the skin. Hairs then travel up through the dermis and epidermis to emerge from the surface of the skin. Most of our bodies are covered in hair follicles. Also, sebaceous glands in the dermis secrete sebum that travels up the hair shaft to protect it, and arrector pili muscles in the dermis allow hairs to move.
10. What kind of skin cancer is a cancer of a type of stem cell? Basal cell carcinoma
11. For the skin and hair, describe one way in which they each protect the body against pathogens. Answers may vary. Sample answer: The skin provides a physical barrier against pathogens because the outer surface consists of tightly packed keratinocytes. Hairs in the nose trap pathogens and prevent them from entering deeper into the body.
12. If sweat glands are in the dermis, how is sweat released to the surface of the body? Sweat glands are in the dermis, but they have ducts that either travel through the epidermis to the surface of the skin directly, or to hair follicles so that sweat can be wicked up along the hair. This allows sweat that is produced in the glands to be released at the surface of the skin.
13. Explain why you think that physicians usually insist that patients remove any nail polish before having surgery.
14. Describe generally how the brain gets touch information from the skin. Answers may vary. Sample answer: Patients should remove nail polish before planned surgery, because the colour of the nail bed gives an indication of the oxygenation of the blood. If the surgical team cannot easily monitor this because of the presence of nail polish, it could seriously affect the health of the patient.