The effects of lipid penetration and removal from subsurface microcavities and cracks at the human cuticle sheath.

An analysis of the light interference patterns produced by the penetration and removal of lipids from the cuticle sheath has shown that cuticle cells in their virgin state have a few intrinsic imperfections in the form of voids and cracks. The experiments also showed that when the cuticle sheath undergoes friction, extension, torsion, and thermal stresses additional microvoids, cavities, and gaps are created at the cuticle cells subsurface. Because of the activity of the sebaceous glands it is quite normal to find these cavities filled with exogenous lipids. Cuticle sheath dehydration, lipid addition, and lipid removal indicate that the viscoelastic deformations giving rise to microcavities can be reversible or irreversible. The presence of exogenous lipids in these cavities was found to be critical in maintaining the mechanical integrity of the cuticle cells. Regions presenting microcavities and cracks produced by reversible deformations were seen to fully recover and heal with the onset of a plasticization effect produced by the synergy of lipids and water. In contrast, microcavities produced by irreversible deformations were always filled with lipids. In both cases the lipids acted as weak adhesives, in particular, in those cavities and gaps opened in the cuticle cell interfaces.