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21.4: The Integumentary System

Difficulty Level: At Grade Created by: CK-12
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Lesson 21.4: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. The skin is the major organ of the integumentary system.

_____ 2. The average square inch of skin has 65 sweat glands.

_____ 3. The average square inch of skin has 60,000 pigment-producing cells.

_____ 4. The skin consists of two distinct layers.

_____ 5. There are no nerve endings or blood vessels in the epidermis.

_____ 6. Melanin is a yellow pigment.

_____ 7. UV light decreases melanin output.

_____ 8. The dermis is made of tough connective tissue.

_____ 9. Sebum increases the growth of microorganisms on the skin.

_____ 10. The skin helps regulate body temperature.

_____ 11. One common problem of the skin is acne.

_____ 12. Acne is caused by a virus.

_____ 13. Skin cancer is caused mainly by excessive exposure to UV light.

_____ 14. People with lighter skin are at greater risk of developing skin cancer.

_____ 15. Skin cancers are generally symmetrical.

Lesson 21.4: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

Functions of the Skin

The skin has multiple roles in the body. Many of these roles are related to homeostasis. The skin’s main functions are preventing water loss from the body and serving as a barrier to the entry of microorganisms. In addition, melanin in the skin blocks UV light and protects deeper layers from its damaging effects.

The skin also helps regulate body temperature. When the body is too warm, sweat is released by the sweat glands and spreads over the skin surface. As the sweat evaporates, it cools the body. Blood vessels in the skin also dilate, or widen, when the body is too warm. This allows more blood to flow through the skin, bringing body heat to the surface, where it radiates into the environment. When the body is too cool, sweat glands stop producing sweat, and blood vessels in the skin constrict, or narrow, thus conserving body heat.


1. What are the skin's two main functions?

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2. What is the function of melanin in the skin?

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3. How does sweat regulate body temperature when the body is too warm?

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4. How do blood vessels in the skin regulate body temperature when the body is too cool?

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Lesson 21.4: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. The average square inch (6.5 cm2) of skin has how many blood vessels?
    1. 10
    2. 20
    3. 30
    4. 40
  2. Exposure to UV light stimulates the skin to produce which vitamin?
    1. A
    2. B
    3. C
    4. D
  3. Melanin in the skin blocks
    1. water.
    2. incadescent light.
    3. UV light.
    4. oxygen.
  4. Acne affects approximately what percent of teens?
    1. 30
    2. 55
    3. 75
    4. 85
  5. Skin cancers
    1. are generally asymmetrical.
    2. have irregular borders.
    3. may be very dark in color.
    4. all of the above
  6. The main component of hair is
    1. keratin.
    2. hemoglobin.
    3. myoglobin.
    4. insulin.
  7. Which of the following are functions of hair?
    1. prevents dust particles from reaching the lungs
    2. prevents heat loss from the body
    3. provides sensory input
    4. all of the above
  8. Which of the following are located in the dermis?
    1. sebaceous glands
    2. sweat glands
    3. hair follicles
    4. all of the above

Lesson 21.4: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.


_____ 1. tough, fibrous protein produced by skin cells

_____ 2. lower layer of the skin, located directly beneath the epidermis

_____ 3. structure where hair originates

_____ 4. protective, waterproof layer of skin

_____ 5. brownish pigment that gives skin much of its color

_____ 6. condition in which red bumps called pimples form on the skin

_____ 7. outer layer of skin, consisting of epithelial cells

_____ 8. produces the salty fluid called sweat

_____ 9. produces an oily substance called sebum

_____ 10. a fiber that is found only in mammals

_____ 11. includes the skin, nails and hair

_____ 12. disease in which skin cells grow out of control


a. acne

b. dermis

c. epidermis

d. hair

e. hair follicle

f. integumentary system

g. keratin

h. melanin

i. sebaceous gland

j. skin cancer

k. stratum corneum

l. sweat gland

Lesson 21.4: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. The __________________ is the major organ of the integumentary system.

2. The innermost cells of the epidermis are continuously dividing through _________________ to form new cells.

3. The epidermis also contains _______________________, which are cells that produce melanin.

4. The amount of melanin produced is determined by heredity and exposure to ______________ light.

5. The dermis is attached to the epidermis by __________________ fibers.

6. Sweat glands open to the surface through __________________ in the skin.

7. Blood vessels in the skin ______________________ when the body is too warm.

8. The underlying cause of acne is excessive secretion of ______________________.

9. The best way to prevent skin cancer is to avoid UV exposure by using sunscreen and wearing ___________________ clothing.

10. A brown spot on the skin is likely to be a harmless __________________, but it could be a sign of skin cancer.

11. All the organs of the integumentary system help the body maintain __________________.

12. Hair provides ____________________ input when objects brush against it or it sways in moving air.

Lesson 21.4: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Name two common problems of the skin, describing each problem and the underlying cause of each.

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