Chapter 5
The Integumentary System
I. The Skin and the Hypodermis (pp. 106–112, Figs. 5.1–5-5)
A. The skin and its appendages make up the integumentary system; it is the largest of the body organs.
B. Technically, the hypodermis is not part of the integument, but it does share some of the skin’s functions. This
fatty layer lies just deep to the skin.
C. The two distinct regions of the skin are the epidermis and the dermis. (pp. 107–110, Figs. 5.2–5.4)
1. The epidermis is keratinized stratified squamous epithelial tissue. It consists of five layers in thick skin and
four layers in thin skin.
a. Stratum basale
b. Stratum spinosum
c. Stratum granulosum
d. Stratum lucidum (occurs only in thick, hairless skin of palms and soles)
e. Stratum corneum
2. Distinguish each layer of the epidermis by the types of cells present and their specific functions.
3. The leather-like dermis is the second major layer of skin and is composed of strong, flexible connective
tissue.
D. The hypodermis is the fatty layer beneath the skin that primarily contains adipose tissue and areolar connective
tissue. (p. 112, Figs. 5.1–5.2)
E. Flexure lines are deep grooves in the palms, soles, wrists, and ankles. The lines are the result of bending the
skin at the joints.
F. Skin color is the result of three pigments: melanin, carotene, and hemoglobin.
II. Appendages of the Skin (pp. 112–117, Figs. 5.6–5.9)
A. Hair and hair follicles are considered appendages of the skin. Hair follicles are the tubular invaginations of
epidermis from which hairs grow.
B. Hairs are of two types:
1. Terminal hairs typify those on the head and have a growth cycle of approximately four years.
2. Vellus hairs are the body hairs of children and females and have a growth cycle of several months.
C. Sebaceous (oil) glands occur over the entire body except palms and soles and secrete sebum.
D. Sweat (sudoriferous) glands are coiled simple tubular glands, located over the entire skin surface except the
nipples and parts of the external genitalia.
1. Sweat is a filtrate of blood comprised primarily of water with salts and metabolic wastes.
E. Sweat glands are of two types: eccrine and apocrine
1. Eccrine sweat glands are more numerous and produce true sweat.
2. Apocrine sweat glands become active at puberty, secrete a viscous substance, and are localized to the
axillary and genital areas.
a. Sweat from these glands may be used for sexual signaling in mate selection.
b. Secretions from apocrine glands have been identified as human pheromones.
F. Nails are a scalelike modification of the epidermis made of hard keratin.
III. Disorders of the Integumentary System (pp. 118–120, Figs. 5.11–5.12)
A. The most common skin disorders result from microbial infections.
B. In severe burns, the catastrophic loss of body fluids is the foremost threat to life; the second threat is
overwhelming infection.
C. Skin cancer is the most common type of cancer; primarily, it is caused by overexposure to UV rays in sunlight.
1. Basal cell carcinoma is the least malignant and the most common.
2. Squamous cell carcinoma arises from the keratinocytes of the stratum spinosum.
3. Melanoma is the most aggressive type and has the greatest tendency to metastasize.
IV. The Skin Throughout Life (p. 120)
A. Structures of skin develop from several specific sources.
1. Epidermis develops from embryonic ectoderm.
2. Dermis and hypodermis arise from mesoderm.
3. Melanocytes develop from embryonic neural crest cells.
B. Most aspects of skin aging are not intrinsic but are caused by sunlight. Sun-exposed skin is wrinkled, loose,
marked with age spots, and inelastic; protected aged skin is mostly unwrinkled and unmarked.
SUPPLEMENTAL STUDENT MATERIALS to Human Anatomy,
Fifth Edition
Chapter 5: The Integumentary System
To the Student
This chapter relates the specifics of skin anatomy to its myriad of functions. Your concept of an organ is broadened to
include the skin and its appendages, and what an organ it is! None other is so versatile and familiar to us. Our skin
reveals our overall health, age, and emotional state. We are cognizant of our environment, internally and externally.
Skin provides protection in numerous ways. What an amazing material it is to resist heat and cold, harsh chemicals, and
bacteria. Knowledge of skin structure also will better enable you to understand damage to skin from burns and diseases,
such as cancer.
Step 1: Understand the anatomy of the skin and the hypodermis.
- Distinguish between epidermis, dermis, and hypodermis.
- Identify specific types of tissues associated with the skin and the hypodermis, noting individual functions.
- Identify specific types of cells associated with skin structure, noting individual functions.
- Organize the skin and the hypodermis into recognized layers.
- Explain skin color.
Step 2: Describe the appendages of skin.
- Name five general skin appendages.
- For each appendage, describe the structure and relate it to its individual functions.
- Explain how an appendage of the skin is considered as an organ.
Step 3: Learn about disorders of the integumentary system.
- Name two major bodily threats from severe burn.
- Classify burns by severity.
- Explain the rule of nines.
- Identify the major risk factor for skin cancer.
- Identify three types of skin cancer, indicating degree of occurrence and curability.
Step 4: Summarize the skin throughout life.
- Identify embryonic origins for the epidermis, dermis, hypodermis, and melanocytes.
- Describe the skin of a 6-month-old fetus.
- Describe the skin of old age.
- Explain factors causing wrinkles.