The Hair Cuticle

The hair cuticle is the outermost part of the hair shaft. It is formed from dead cells, overlapping in layers, which form scales that strengthen and protect the hair shaft. Although the cuticle is the outermost layer, it is not responsible for the color of the hair. Melanin found in the cortex is the pigment that gives hair its color.

Each cuticle cell contains a thin outer membrane, the epicuticle ( estimated between 50-100 angstroms thick).  This layer is in turn covered by strongly bound lipids (mostly the fatty acid 18-methyleicosanoic acid) called the F-layer. The F layer represents the outermost surface of hair. Beneath the cuticle outer cell membrane are three major layers: the A layer, a resistant layer with a high cystine content (>30%); the exocuticle, sometimes called the B layer, also rich in cystine (~15%); and then the endocuticle, low in cystine content (~3%).   The cystine rich layer create keratin-associated proteins which are robust structures.