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CHAPTER
5
The Integumentary System
Objectives
The Skin
2. Describe the factors that normally contribute to skin color. Briefly describe how changes
in skin color may be used as clinical signs of certain disease states.
Appendages of the Skin
3. List the parts of a hair follicle and explain the function of each part. Also describe the
functional relationship of arrector pili muscles to the hair follicles.
5. Describe the structure of nails.
7. Compare and contrast eccrine and apocrine glands.
Functions of the Integumentary System
8. Describe how the skin accomplishes at least five different functions.
Homeostatic Imbalances of Skin
9. Summarize the characteristics of the three major types of skin cancers.
Developmental Aspects of the Integumentary System
Suggested Lecture Outline
I. The Skin (pp. 150–157; Figs. 5.1–5.4)
A. The skin consists of two regions: the outermost epidermis, an epithelial tissue; and the
inner dermis, a connective tissue (p. 151; Fig. 5.1).
B. The hypodermis, also called the superficial fascia, is subcutaneous tissue beneath the skin
consisting mostly of adipose tissue that anchors the skin to underlying muscle, allows
skin to slide over muscle, and acts as a shock absorber and insulator (p. 151; Fig. 5.1).
C. Epidermis (pp. 151–154; Fig. 5.2)
1. The epidermis is a keratinized stratified squamous epithelium that consists of four cell
types, arranged in four to five layers.
2. Cells of the Epidermis
3. Layers of the Epidermis
a. The stratum basale (basal layer) is the deepest epidermal layer and is the site of
mitosis.
b. The stratum spinosum (prickly layer) is several cell layers thick and contains
keratinocytes, melanin granules, and the highest concentration of dendritic cells.
D. Dermis (pp. 154–156; Figs. 5.3–5.4)
1. The dermis is composed of strong, flexible connective tissue and is well supplied with
blood vessels, nerves, and lymphatic vessels.
2. The dermis is made up of two layers: the thin, superficial papillary layer that forms
II. Appendages of the Skin (pp. 157–162; Figs. 5.5–5.7)
A. Hairs and Hair Follicles (pp. 158–160; Fig. 5.5)
1. Hairs, or pili, are flexible strands produced by hair follicles that consist of dead,
keratinized cells.
a. The main regions of a hair are the shaft, which projects from the skin, and the root,
2. Structure of a Hair Follicle
a. Hair follicles fold down from the epidermis into the dermis and occasionally into
the hypodermis.
b. The deep end of a hair follicle is expanded, forming a hair bulb, which is sur-
rounded by sensory nerve endings called a hair follicle receptor, or root hair plexus.
3. Types and Growth of Hair
a. Hairs can be classified as pale, fine vellus hairs, or longer, more coarse terminal
hairs.
age.
4. Hair Thinning and Baldness
a. After age 40, hair is not replaced as quickly as it is lost, which leads to hair thinning
and some degree of balding, or alopecia, in both sexes.
B. Nails (p. 160; Fig. 5.6)
1. A nail is a scalelike modification of the epidermis that forms a protective covering on
the dorsal side of the distal finger or toe.
C. Sweat (Sudoriferous) Glands (pp. 160–161; Fig. 5.7)
1. Eccrine, or merocrine, sweat glands produce true sweat and are abundant on the palms
of the hands, soles of the feet, and forehead.
a. Secretion of eccrine glands is regulated by the sympathetic nervous system and is
D. Sebaceous (Oil) Glands (pp. 161–162; Fig. 5.7)
1. Sebaceous glands secrete sebum, an oily secretion, and are found all over the body,
except the palms of the hands and soles of the feet.
3. Secretion by sebaceous glands is stimulated by hormones.
III. Functions of the Integumentary System (pp. 162–164)
A. Protection (pp. 162–163)
1. Chemical barriers include skin secretions that inhibit bacterial growth and melanin that
protects skin from UV damage.
B. The skin plays an important role in body temperature regulation by using the sweat
glands of the skin to cool the body and constriction of dermal capillaries to prevent heat
loss (p. 163).
C. Cutaneous sensation is made possible by cutaneous sensory receptors, which are part of
the nervous system, in the layers of the skin (p. 163).
IV. Homeostatic Imbalances of Skin (pp. 164–167; Figs. 5.8–5.10)
A. Skin Cancer (pp. 164–165; Fig. 5.8)
1. Basal cell carcinoma results from invasive proliferation of cells of the stratum basale
and is the least malignant and the most common skin cancer.
B. Burns (pp. 165–167; Figs. 5.9–5.10)
1. A burn is tissue damage resulting from intense heat, electricity, radiation, or certain
chemicals, all of which denature cell proteins and cause cell death to affected areas.
V. Developmental Aspects of the Integumentary System (p. 167)
A. The epidermis develops from the embryonic ectoderm, and the dermis and the
hypodermis develop from the mesoderm.
B. By the end of the fourth month of development the skin is fairly well formed.
Cross References
Additional information on topics covered in Chapter 5 can be found in the chapters listed below.
1. Chapter 3: Desmosomes
2. Chapter 4: Stratified squamous epithelium, keratinized; basement membrane; loose
(areolar) connective tissue; dense irregular connective tissue; fibers in matrix of connec-
tive tissue; simple coiled tubular glands; simple branched alveolar glands; merocrine
glands; holocrine glands
Lecture Hints
1. The strata basale and spinosum are often referred to collectively as the growing layers
(stratum germinativum). Some authors consider the stratum germinativum to be only the
stratum basale. Students are easily confused if terminology is not consistent between
lecture, text, and lab test.
4. Discuss the activity of melanocytes, melanin production, and degree of ultraviolet radia-
tion. Point out the genetic basis of melanocyte activity and the geographic distribution of
ancestral humans as an explanation for racial variation. Explain the effect of the degree
of exposure to UV radiation and tanning in individuals.
Activities/Demonstrations
1. Audiovisual materials are listed in the Multimedia in the Classroom and Lab section of
this Instructor Guide (p. 387).
2. Show the students a picture of a heavily wrinkled person. Ask them to list all the factors
that have contributed to the skin deterioration seen.
Critical Thinking/Discussion Topics
1. What role does the skin play in the regulation of body temperature?
2. Why exactly can animals with thick fur, such as Alaskan huskies, resist extremely cold
temperatures?
58 INSTRUCTOR GUIDE FOR HUMAN ANATOMY & PHYSIOLOGY, 9e Copyright © 2013 Pearson Education, Inc.
6. The air is 80˚F and the lake temperature is 70˚F. Why do you first feel cold when you
enter the water? Why do you feel chilled when exiting the water?
7. Why does axillary hair not grow as long as hair on the scalp? How long would scalp hair
grow if it were not cut?
11. Individuals living in Ohio may be able to go out into the sun for three hours and not burn,
but if they go to Florida during spring break, they may become sunburned after only two
hours. Why?
12. Describe the difference between the A and B types of ultraviolet rays relative to skin
damage.
1. Explore the literature on the latest techniques and materials such as synthetic skin and
bioprinted skin used for skin grafting.
2. The long-term effects of sunburn seem to include severe wrinkling of the skin and skin
cancer. What are the latest statistics on this problem and what has been done to correct it?
List of Figures and Tables
All of the figures in the main text are available in JPEG format, PPT, and labeled & unlabeled
format on the Instructor Resource DVD. All of the figures and tables will also be available in
Transparency Acetate format. For more information, go to www.pearsonhighered.com/educator.
Figure 5.1 Skin structure.
Figure 5.2 The main structural features of the skin epidermis.
Figure 5.6 Skin appendages: Structure of a nail.
Figure 5.7 Skin appendages: Cutaneous glands.
Answers to End-of-Chapter Questions
Multiple-Choice and Matching Question answers appear in Appendix H of the main text.
Short Answer Essay Questions
14. Generally not. Most fibald” men have fine vellus hairs that look like peach fuzz in the
fibald” areas. (p. 159)
15. On an extremely hot, sunny summer day your integumentary system will function to
maintain homeostasis in several ways. First, your skin will sweat. Sweating is a form of
16. First-degree burns affect only the epidermis; second-degree burns affect down to the der-
mis; and third-degree burns affect down to the subcutaneous tissue and muscle. (p. 166)
17. Hair formation begins with an active growth phase, followed by a resting phase. After the
resting phase a new hair forms to replace the old one. Factors that affect growth cycles
19. Wrinkling is due to the loss of elasticity of the skin, along with the loss of the subcutane-
ous tissue, and is hastened by prolonged exposure to wind and sun. (p. 167)
20. a. When a blocked sebaceous gland becomes infected, it produces a pimple. (p. 162)
b. Noninfectious dandruff is the normal shedding of the stratum corneum of the scalp.
(p. 154)
e. A freckle is a small area of pigmentation in the epidermis, caused by an accumulation
of melanin. (p. 157)
21. (a) Porphyria. Porphyria victims lack the ability to form the heme of Hb. Buildup of
22. Stratum corneum cells are dead. By definition, cancer cells are rapidly dividing cells.
(pp. 154, 164)
23. Nail body: the visible attached portion of the nail. Nail root: the embedded portion of the
nail. Nail bed: the epidermis that extends beneath the nail. Nail matrix: the proximal,
thickened portion of the nail bed responsible for nail growth. Eponychium: the cuticle. If
Critical Thinking and Clinical Application Questions
1. His long-term overexposure to ultraviolet radiation in sunlight is considered a risk factor
for the development of skin cancer. The ABCD rule is a set of diagnostic criteria used to
2. The two most important problems encountered clinically with a victim of third-degree
burns are a loss of body fluids resulting in dehydration and an electrolyte imbalance, and
3. Chronic physical irritation or inflammation can lead to excessive hair growth in the
region affected due to an increase in blood flow to the area. (p. 159)
4. The appendectomy incision ran parallel to the less dense filines of cleavage” that separate
bundles of collagen fiber in the dermis. The gallbladder incision cut across them. (p. 155)
5. A woman such as this, even though she lives in a climate with ample direct sunlight, has
Suggested Readings
Christensen, Damaris. fiHair Today, Gone Tomorrow?” Science News 160 (16) (Oct. 2001):
254–255.
Da Forno, P. D., and G. S. Saldanha. fiMolecular Aspects of Melanoma.” Clinics in
Laboratory Medicine 31 (2) (June 2011): 331–343.
Garnick, Marc. fiThe Sunshine D-lemma.” Harvard Health Letter 3 (Aug. 2008): 6–7.
Kirchweger, Gina. fiBlack and White.” Discover 22 (2) (Feb. 2001): 32–33.
Ko, S. H., et al. fiThe Role of Stem Cells in Cutaneous Wound Healing: What Do We Really
Know?” Plastic and Reconstructive Surgery 127 (Suppl. 1) (Jan. 2011): 10S–20S.
Krueger, James G. fiTreating Psoriasis with Biologic Agents.” Science and Medicine 8 (3)
(May/June 2002): 150–161.
Kwasniak, L. A., and J. Garcia-Zuazaga. fiBasal Cell Carcinoma: Evidence-Based Medicine
and Review of Treatment Modalities.” International Journal of Dermatology 50 (6) (June
2011): 645–658.
