Hair anatomy: the shaft

The cells produced by the hair bulb gradually keratinized and peek out from the surface of the scalp… Here is the hair shaft, whose structure is divided into 3 concentric parts: 

 ·         the medulla is the inner part of the hair, formed by cells arranged in a column. It is the medulla that determines the shade of the hair (dark or light); 
·         the cortex is the middle part of the hair shaft, formed by elongated cells that determine its resistance. Pigment granules are found in the interstices between these cells: just as the medulla determines the shade, the cortex determines the color of the hair (and also their shape and consistency);  
·         the cuticle is the external part of the hair, formed by cells with a particular flaky arrangement, necessary for its protective function.  The consistency of the cuticle determines the appearance of the hair: if it is damaged, the hair will appear dull or brittle. 

Read also:
Hair anatomy: the bulb and the root