Can someone explain to me how my nails are strong but my hair is very fragile I don't understand?

[Skyler123]

My nails are very strong and it takes a lot to break them. They usually just break off on their own when they get about half an inch long. But my hair is a different story. It breaks easily plus I have split ends. No matter how much I clip my ends my split ends never go away which leads me to believe that my hair is naturally prone to splitting. It sheds like crazy and its making growing it out longer very difficult and frustrating. I know that the same thing that causes nails to grow is the same that makes hair grow. So why am I having issues growing/maintaining length in my hair? My nails are very strong and durable and I have no problem growing them. I dont understand...
@Meep Meep. I don't do anything to my hair. I will however look into vitamins. That may be the issue back when I was exercising a lot and eating fruit my hair would actually grow quite rapidly.