During which phase of hair growth does the hair bulb move up through the follicle?

The hair bulb moving up through the follicle is a characteristic feature of the anagen phase of hair growth. During this phase, which is also known as the growth phase, hair actively grows and is deeply anchored in the follicle. As the hair bulb produces new cells, the hair strand continues to elongate and rise up through the follicle. This phenomenon is crucial for hair development, as it allows for the continuous production and renewal of hair.

In contrast, during the catagen phase, hair growth slows, and the hair follicle begins to shrink, which separates the hair from the bulb. The telogen phase is considered the resting phase, where hair is neither growing nor moving up through the follicle but is instead preparing to shed. The exogen phase refers to the process of shedding the old hair, which occurs after the telogen phase and does not involve any upward movement through the follicle.

Thus, the transition and growth processes that characterize the anagen phase ultimately lead to the hair bulb's upward movement within the follicle, marking it as the correct phase in this context.