Milady Cosmetology Practice Exam

Which layer of hair must have its side bonds broken to change the natural wave pattern?

1. Cortex

2. Cuticle

3. Medulla

4. Outer Layer

The correct answer is: Cortex

The cortex is the correct choice because it is the main structural layer of the hair that contains the fibrous protein and is responsible for the hair's strength, durability, and moisture. The cortex also houses the hair's natural wave pattern, which is determined by the arrangement of the keratin proteins within it. To alter the natural wave pattern of the hair, such as during perming or relaxing treatments, the disulfide bonds (a type of side bond) within the cortex must be broken and then reformed. This process allows the hair to take on a new shape or style. The other layers, such as the cuticle, serve as a protective outer layer and do not actively influence the internal structure and wave patterns of the hair. The medulla, while present in some hair types, is often absent in finer hair and does not play a role in the wave pattern. Therefore, breaking the side bonds within the cortex is essential for changing the natural wave pattern.