Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

5. Integumentary System

Hair

Anatomy & Physiology

5. Integumentary System

Hair

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1:17 minutes

Problem 31

Textbook Question

Many people change the natural appearance of their hair, either by coloring it or by altering the degree of curl in it. Which layers of the hair do you suppose are affected by the chemicals added during these procedures? Why are the effects of the procedures not permanent?

Verified step by step guidance

Understand the structure of the hair: Hair is composed of three layers—cuticle (outermost layer), cortex (middle layer), and medulla (innermost layer). The cuticle protects the inner layers, while the cortex contains keratin and melanin, which determine hair's strength, texture, and color.

Identify the layers affected by chemical treatments: Hair coloring and curling/straightening treatments primarily affect the cortex. The cortex contains the pigment (melanin) responsible for hair color and the keratin protein structure that determines the hair's shape and texture.

Explain how chemicals interact with the cortex: Hair coloring chemicals penetrate the cuticle to reach the cortex, where they alter the melanin to change the hair color. Curling or straightening treatments break and reform the disulfide bonds in keratin within the cortex, changing the hair's shape.

Discuss why the effects are not permanent: Hair grows continuously from the follicle, and new hair is unaffected by the chemical treatments. Additionally, environmental factors like washing, UV exposure, and mechanical stress gradually degrade the chemical changes, causing the hair to revert to its natural state over time.

Conclude with the role of the cuticle: The cuticle acts as a protective barrier, but it can be damaged during chemical treatments, leading to weakened hair. Proper care is essential to maintain hair health after such procedures.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hair Structure

Hair is composed of three main layers: the cuticle, cortex, and medulla. The cuticle is the outermost layer, providing protection, while the cortex contains the majority of the hair's pigment and strength. The medulla is the innermost layer, which may be absent in some hair types. Understanding these layers is crucial for comprehending how chemical treatments affect hair.

Chemical Hair Treatments

Chemical treatments, such as coloring and perming, primarily target the cortex, where the hair's natural pigment and structure are located. These processes involve breaking and reforming the disulfide bonds in the hair's protein structure, allowing for changes in color and curl. The specific chemicals used can alter the hair's physical and chemical properties temporarily.

Hair Growth Cycle

The hair growth cycle consists of three phases: anagen (growth), catagen (transition), and telogen (resting). Since hair is continuously growing and shedding, the effects of chemical treatments are not permanent because new hair growth will eventually replace treated hair. This cycle explains why color and curl alterations fade over time as untreated hair emerges.