|MadSci Network: Anatomy|
Thanks for your interesting question. Human fingernails are not made of stiff hair but are actually made from skin cells.
Nails grow from a "growth plate" located at the base of the nail. It's the half-moon shaped area at the base of the nail near where the skin connects. Nails are fomed by special cells called epithelium. Epithelial cells grow from the growth plate and as they mature, they are pushed outward. During growth they die and the inside of the cells become filled with a hard protein called "Keratin". It is the keratin that makes our nails hard and tough.
Thanks again for your question.
Incidentally, keratin is one of the predominant proteins that make up hair. So, although fingernails are not made of 'stiff hair' they contain lots of keratin, just like strands of hair.
Try the links in the MadSci Library for more information on Anatomy.