Final answer:
The anagen phase of hair growth lasts from three to five years. This phase is characterized by rapid cell division at the root of the hair, contributing to the lengthening of the hair shaft. After this phase comes the catagen phase and then the telogen phase, completing the hair growth cycle.
Step-by-step explanation:
The anagen phase generally lasts from three to five years. During this time, the cells at the root of the hair divide rapidly, which contributes to the growth of the hair shaft. The anagen phase is the first of three stages in the hair growth cycle and is followed by the catagen phase, a transitional period, and then the telogen phase, where the hair follicle is at rest. In the anagen phase, the hair typically grows at a rate of 0.3 mm per day, and an average of 50 hairs are lost and replaced daily. Factors such as hormonal changes, dietary changes, the aging process, and the influence of hormones can cause hair loss when more hair is shed than is replaced.