Why do Nail Plates Snap off at the Free Edge Rather than Split?

Internal Structure of Nail Cells and the Arrangement of Keratin Fibrils

There are many reinforcing bonds holding nails cells together. These form randomly in all directions, so it would be expected that the plate would be equally resistant to cracking in all directions. Clearly, that is not the case. The nail plate is highly prone to breaking in one direction, across the width of the plate as shown in the banner Image (above). Only in an unusual circumstance does a break or split occur down the length of the plate. The reason for this is the internal structure of each nail cell.

Crack Propagation and the Role of Keratin Fibril Arrangement

Each nail cell is filled with many short strands of keratin called “fibrils” and they have the appearance of tiny fibers. These fibers aren’t randomly distributed, but instead are uniformly stacked into neat piles, much like logs of wood are stacked. These stacks of fibrils lay across the width of the nail plate with their ends pointing toward the sidewalls (see image above). This arrangement makes it much easier for a crack to travel between the fibrils, rather than across or through them. This keratin fiber arrangement leads the cracks to turn toward the sidewalls and prevents cracks from spreading down the length of the plate.

Preventing Catastrophic Injuries: How Nail Plates Protect Themselves

Cracks move like water flowing downhill; they take the path of least resistance. This helps to prevent the nail plate from splitting open to expose the underlying nail bed. In this way, the nail plate protects itself from catastrophic injuries that can lead to serious infections. The plate can split down its length, but when it does, often the crack follows a deep groove that formed in the nail plate.

Conclusion

The unique internal structure of nail cells and the arrangement of keratin fibrils play a crucial role in the way nail plates break or snap off.

The presence of reinforcing bonds in random directions would suggest equal resistance to cracking in all directions, but that is not the case.

The stacks of fibrils across the width of the nail plate create an organized structure that allows cracks to travel between the fibrils rather than across or through them. This arrangement directs cracks towards the sidewalls, preventing them from spreading down the length of the plate.

By following the path of least resistance, the nail plate safeguards itself from catastrophic injuries that could lead to severe infections. Although the plate can still split down its length, it often does so along a deep groove that has formed, further protecting the underlying nail bed.

Understanding the internal structure of nail cells sheds light on the remarkable ability of nail plates to withstand forces and maintain their integrity.

FAQ’s

Q: Why do nail plates snap off at the free edge rather than splitting?
A: Nail plates primarily snap off at the free edge due to the unique internal structure of nail cells. The arrangement of keratin fibrils, stacked across the width of the nail plate, creates a path of least resistance for cracks to travel between the fibrils rather than across or through them. This directed crack propagation towards the sidewalls prevents splitting along the length of the plate.

Q: How does the internal structure of nail cells contribute to their strength?
A: The internal structure of nail cells plays a significant role in the strength of nail plates. The presence of reinforcing bonds that form randomly in all directions provides overall resistance to cracking. However, the organized arrangement of keratin fibrils, resembling stacked logs of wood, further enhances this strength. By uniformly stacking the fibrils across the width of the nail plate, cracks are more likely to follow the path between the fibrils rather than across them, thereby maintaining the plate’s integrity.

Q: Can nail plate splitting lead to serious infections?
A: Yes, nail plate splitting can potentially lead to serious infections. However, it is important to note that nail plates have mechanisms in place to protect themselves from such catastrophic injuries. When splitting does occur, it often follows a deep groove that has formed in the nail plate, minimizing the exposure of the underlying nail bed. This protective measure helps reduce the risk of infections. Nevertheless, it is essential to maintain proper nail hygiene and promptly address any splits or injuries to prevent complications.