A discrete transition zone between cuticle and cortex layers of a human hair fibre: changes observed in the presence of breast cancer.

Attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy of hair fibres shows a discrete transition zone (DTZ) between the hard protective cuticle layer and the softer elongated cortical cells of the cortex. The DTZ is composed of flattened orthocortical cells located on the outer perimeter of the cortex and appears to range in thickness between 2 and 3.6 μm.