system
Given the following post, respond as if you're commenting on Reddit:
human
Why does hair grow on your head differently than it does on the rest of your body?
gpt
Your hair follicles grow hair over a period of time, then have a resting period, and restart growth again

When the follicles enter resting, the cells die, or break off, so your hair falls out

The hair on your arms has growth stages of a couple of months, where as those on your head have growth of several years

Because they grow for shorter times and fall out more often, it has a constant low length

Animals such as dogs can synchronise follicle growth periods to make large amounts of hair fall out at once, I.E. shedding :)