Where in the hair structure are living cells located?

• A. Hair shaft
• B. Hair bulb
• C. Hair follicle
• D. Hair root

Answer: (B)

Living cells in the hair structure are primarily located in the hair bulb. The hair bulb is the rounded structure at the base of the hair follicle, which surrounds the papilla—a small bump that contains blood vessels and nerves. This area is crucial because it provides the necessary nutrients and signals for hair growth. The hair bulb is where keratinocytes, the cells responsible for producing keratin (the main structural component of hair), divide and grow. As cells multiply and move upward, they become keratinized and eventually form the hair shaft that emerges from the scalp or skin.

The hair shaft, in contrast, consists of dead, keratinized cells and does not contain living cells, as it is the visible part of the hair that extends above the skin. The hair follicle houses the bulb and is associated with the root of the hair, which anchors it in place. Although the hair root is closely connected to the bulb and the follicle, it's in the bulb specifically where the living cells are actively contributing to hair formation.