The Integumentary System: the Protective Covering

Chapter

THE INTEGUMENTARY 8 SYSTEM: THE PROTECTIVE COVERING

LEARNING OBJECTIVES

➯ Discuss the functions of the integumentary ➯ Describe the structure and growth of hair system and nails ➯ List and describe the layers of the skin ➯ Explain how the body regulates temperature through the integumentary system ➯ Explain the healing process of skin

TEACHING STRATEGIES

1. When discussing one of the functions of the skin—protection or a barrier against pathogen invasion, for example—make the point that

FACTOIDS

1. The word integument comes from the Latin meaning “to cover.” 2. New shoes may cause the skin of the foot to blister. This is because the

ETHICAL DILEMMAS

1. The greatest ethical dilemma that comes from the integumentary system arises from skin color. What possible reason could anyone have

ANSWERS TO TEST YOUR KNOWLEDGE Test Your Knowledge 8–1 Answers, p. 176 1. a. epidermis b. dermis c. subcutaneous fascia (hypodermis) 2. a. prevention of fluid loss b. prevention of infection c. vitamin D production d. temperature regulation e. sensory input f. fat storage

3. d 4. c 5. c Test Your Knowledge 8–2 Answers, p. 182 1. b 2. c 3. b 4. d

ANSWERS TO THE CASE STUDY, P. 188

She has a contact dermatitis, probably caused by poison ivy. The vesicles have begun to form around her eyes because of contact spreading. When she scratches the vesicles on her legs and then rubs her eyes, she spreads the poison ivy.

ANSWERS TO REVIEW QUESTIONS, P. 188

Multiple Choice 1. a, 2. b, 3. c, 4. d, 5. b

Fill in the Blank 1. epidermis; dermis; hypodermis 2. eccrine; apocrine 3. sebum 4. freckles 5. bilirubin

Short Answer 1. The skin has several functions. It functions as a barrier against bacteria entering the body. The skin, when exposed to sun, produces vitamin D. Because the skin is keratinized, it is waterproof and helps prevent fluid loss. Body fluids can only pass through the skin as sweat. The skin also helps control body temperature. Blood vessels in the skin dilate, sending more blood to the skin if your temperature rises. You also sweat to increase evaporative cooling. Blood vessels in the skin constrict, decreasing blood flow to the skin, if your body temperature falls. Fat storage as well as sensory input are also skin functions. 2. The epidermis is composed of stratified squamous epithelial cells. In the deepest sublayer, the basal layer (stratum basale), the cells are living. All the cells of the epidermis are born in the basal layer. After the cells are born, they move toward the surface layer, the horny layer

(stratum corneum). As they move toward the surface, the cells die and become filled with keratin. Dead cells are sloughed from the surface of the skin and replaced every 2 to 4 weeks. 3. Melanin is a pigment that shields the nuclei of skin cells from UV radiation. The source of most UV radiation is sunlight. So, as sunlight exposure increases, so does your body’s attempt to protect against UV damage. 4. Burns are classified by depth and extent. Burn depth is divided into four classes. First-degree burns are superficial damaging only the epidermis. Second-degree burns are more serious, damaging the epidermis and part of the dermis. First- and second-degree burns are partial thickness burns. Third-degree burns burn through the epidermis and the dermis, completely destroying the skin. Fourth-degree burns destroy muscle and bone. Third- and fourth-degree burns are full- thickness burns. Extent of a burn is expressed as percentage of body burned. The rule of nines is used to estimate the percentage of the body that is burned. 5. There are several skin accessory structures. Sweat glands secrete water either to regulate body temperature or as a sexual attractant. Hair follicles produce hair and are associated with arrector pili muscles, which create goose bumps when the air is cold. Sebaceous glands, which secrete sebum (oil) to lubricate the skin, are also associated with hair follicles.