Where do mitotic cells in the hair begin their growth activity?

Where do mitotic cells in the hair begin their growth activity?

• A. Cortex
• B. Matrix
• C. Cuticle
• D. Medulla

Answer: (B)

Mitotic activity in hair starts in the hair matrix, the layer at the base of the follicle inside the hair bulb. Here, rapidly dividing keratinocytes produce new cells that will differentiate and migrate upward to form the hair shaft and its surrounding structures. As these cells differentiate, they give rise to the cortex, medulla, and cuticle of the hair; once they reach these parts, they stop dividing. The cortex, medulla, and cuticle are mature, keratinized portions of the hair, not sites of cell division.

Mitotic activity in hair starts in the hair matrix, the layer at the base of the follicle inside the hair bulb. Here, rapidly dividing keratinocytes produce new cells that will differentiate and migrate upward to form the hair shaft and its surrounding structures. As these cells differentiate, they give rise to the cortex, medulla, and cuticle of the hair; once they reach these parts, they stop dividing. The cortex, medulla, and cuticle are mature, keratinized portions of the hair, not sites of cell division.