Final answer:
About 85-90% of hair on a person's scalp is in the Anagen stage at any given time. This growth phase is the longest, lasting several years, and it's characterized by active division and elongation of the hair cells.
Step-by-step explanation:
The question addresses the hair growth cycle stages and the proportion of hair in each stage at any given time. During the Anagen stage, which is the active growth phase, hair cells divide rapidly, contributing to the lengthening of the hair shaft. This phase lasts several years, typically between 2 to 7 years. Thereafter, the hair enters the Catagen phase, a brief transitional period, followed by the Telogen phase, a resting stage that culminates in the shedding of hair before the Annagen stage recommences.
On average, it is estimated that about 85-90% of the hair on an individual's scalp is in the Anagen stage at any one time. This high percentage reflects the long duration of the Anagen phase relative to the other stages in the hair growth cycle. As a result, a majority of hair strands are actively growing, thus demonstrating the continuous nature of hair cycling in humans.