American Academy of Professional Coders (AAPC) Practice Exam

At what week does a developing fetus have its lifetime supply of hair follicles?

1. 20 weeks

2. 22 weeks

3. 24 weeks

4. 26 weeks

The correct answer is: 22 weeks

The correct answer is 22 weeks. During pregnancy, the development of hair follicles occurs at various stages, and by around the 22nd week of gestation, the fetus has generated the majority of the hair follicles it will have for its entire life. This process is part of the fetal development that gives rise to hair covering the skin, known as lanugo, which begins to form as early as 14 to 16 weeks but peaks around this 22-week mark. Each hair follicle is established during this critical timeframe, marking a significant milestone in the development of the fetus's integumentary system. Other weeks mentioned do not represent the specific point when the lifetime supply of hair follicles is fully formed; thus, they are not the correct choice. Each of those other weeks corresponds to different stages of development for other systems or structures, but it is at 22 weeks that the hair follicles are essentially finalized for the future.