When people grow up to juvenescent phase, the amount of stem cells in the body falls sharply, due to the apoptosis of adult stem cell under the pressure of internal environment.

• 人的成长发育进入青年期，机体内各种成体干细胞的数量急剧减少，起原因成体干细胞在体内外环境的压力下逐渐凋亡；