Delaware Cosmetology and Barbering Practice Exam

Which hair structure determines the thickness of individual strands?

1. Cortex

2. Medulla

3. Cuticle

4. Follicle

The correct answer is: Medulla

The medulla is the innermost layer of the hair and plays a significant role in determining the thickness of individual hair strands. The presence and size of the medulla can vary from one hair strand to another. In some hair types, particularly in coarser strands, the medulla is more pronounced, contributing to the overall thickness and density of the hair. In contrast, the cortex, while crucial for the strength and color of the hair, does not directly determine the thickness itself—though it surrounds the medulla. The cuticle is the outermost protective layer of the hair and primarily functions to protect the inner layers, but it does not influence the strand thickness. The follicle is the structure in the skin from which the hair grows and involves the live part of the hair, but it does not affect the thickness of the individual strands once they have emerged from the scalp. Thus, the medulla is the key structure that determines how thick a strand of hair is.