I thought I'd go for something more bizarre with this series, so I chose to show a single hair. Hair plays a very important part in the human body, & if viewed in one of those cross-sections of skin, it almost looks like a leafless stalk. I used a brown hair, since that's shown most often in diagrams. The red sleeve on the doll's arm represents the tiny muscle every hair on the human body has attached to it. (This is what causes the hairs on your skin to stand up when you're cold or scared). Her boots are supposed to be the tiny blood vessel every single hair is attached to. These provide nutrients to keep the hair shaft healthy & allow it to keep on growing. I added a few extra tiny blood vessels using those long ribbons.
Human hair is made from a protein called Keratin, the same protein that makes up finger/toenails. If you look at a hair in an electron-microscope photo, you'd see what looks like a palm-tree trunk--scales of keratin growing up in layers over a central shaft.
I actually read in a human body book on skin (hair was included & had its own chapter), that even today, scientists have no idea why humans have long hair on their heads & nowhere else.