Cracked fingernails and why they don't split

Fingernails strong by design

If you've ever wondered why cracked fingernails don't just painfully split down the middle or simply been grateful that they don't, Dr. Roland Ennos can tell you why.

Fingernails have three fibrous layers. The outer and inner layer have fibers running in all directions that give the fingernail its flexibility. The outermost layer also wraps around the sides to help prevent cracks from forming in the first place. The thick middle layer has fibers that traverse the nail, sending those cracks laterally instead of into the quick.

To test his theory of nail mechanics, Dr. Ennos attached instrumented scissors to a measuring device and found that nails were twice as difficult to cut towards the base as across it...Consequently cracks are deflected around the end of the nail, protecting the nail bed from damage.