California Cosmetology Written ExamChemical Texture ServicesEasy
Which layer of the hair shaft contains the majority of the disulfide, hydrogen, and salt bonds responsible for hair's strength and elasticity, making it the primary target of chemical texture services?
- ACuticle
- BCortex
- CMedulla
- DFollicle
Show answer & explanationAnswer & explanation
Correct answer: B. Cortex
The cortex is the middle layer of the hair shaft and houses the keratin protein chains held together by disulfide, hydrogen, and salt bonds. Perms and relaxers must penetrate the cuticle to reach the cortex, where the actual bond-breaking and reforming occurs.
Why the other options are wrong
- A. The cuticle is the protective outer layer, not the site of bond restructuring.
- C. The medulla is the innermost, often absent layer with no known cosmetic function.
- D. The follicle is a skin structure that houses the hair root, not part of the hair shaft's bond structure.
Cortex
The middle layer of the hair shaft containing keratin protein chains linked by disulfide, hydrogen, and salt bonds; the target of all chemical texture services.
- Contains ~90% of hair's mass
- Holds disulfide, hydrogen, and salt bonds
- Determines strength, elasticity, and curl pattern
Memory trick: 'Cuticle Coats, Cortex Controls' — cuticle protects, cortex holds the bonds