Where does hair growth primarily begin?

Hair growth primarily begins at the hair bulb. The hair bulb is the rounded structure at the base of the hair follicle, which houses the living cells that divide and multiply to produce the hair shaft. This process of cell division is essential for hair growth, as new cells push older ones upward, forming the hair shaft that is visible above the skin.

The hair bulb contains vital components such as dermal papilla, which is responsible for providing nutrients and signaling for growth. However, the actual starting point of hair growth itself is located at the hair bulb, where the hair formation process initiates.

The hair shaft, on the other hand, is the elongated part of the hair that is visible above the skin and does not play a role in hair growth initiation. The follicle opening refers to the external part of the follicle where the hair emerges, but it is not where growth actually occurs. While the dermal papilla provides crucial support and nourishment, it is part of the hair bulb and indicates that growth is centered there. Thus, the correct answer highlights the key anatomical structure involved in the initiation of hair growth.