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The cortex, also known as the cortex, is the middle part of the hair shaft and plays a central role in the physical properties of the hair, such as strength, color and texture. It is located between the outer layer of the hair, the cuticle, and in some hair types an inner core, the medulla. The cortex consists mainly of long chains of keratin proteins connected by sulphur bridges. This protein structure gives the hair its elasticity and strength.
The cuticle is the outer layer of the hair shaft and consists of flat, overlapping scales that protect the hair from damage and give it shine. The integrity of the cuticle is crucial to the health of the hair, as damage to this layer can lead to dryness, breakage and a dull appearance.
Melanin, the pigment responsible for the color of hair (and skin), is also found in the cortex. There are two main types of melanin: eumelanin, which provides brown to black pigments, and pheomelanin, which provides red and yellow pigments. The specific mixture and concentration of these pigments determine the natural color of the hair.
The medulla, although not present in all hair types, is the innermost part of the hair shaft and consists of a loose arrangement of cells and air pockets. Its function is not fully understood, but it may play a role in thermal insulation.
Together, these components form the structure of the hair and determine its physical properties. The cortex, with its rich keratin structure and melanin content, is responsible for essential properties such as the hair’s strength, elasticity and color. The cuticle protects these inner layers and contributes to the overall appearance of the hair, while the medulla plays an additional, albeit less understood, role.
