The cortex is the main structure that gives your hair its strength and elasticity and houses the pigment melanin that determines your natural hair color.
From 2-D X-ray diffraction, standard signals were identified in both the equatorial plane and along the axial axis of hairs, possibly related to the coiled-coil phase of keratin proteins and the formation of intermediate filaments in the cortex.
Split Ends
Split ends can be seen at the ends of your hair and result from when the cuticle layer breaks down, exposing its inner cortex and making it vulnerable to damage. These split ends may have multiple causes, including over-processing with heat-styling tools or chemicals, environmental stressors, and physical trauma.
Traditional, or primary, split ends are among the most prevalent forms of split end damage, where cortical cells separate but still hold together essentially. This form usually arises due to dryness and can be avoided with regular trims, hydration, and by preventing heat tools or overprocessing your hair.
Tree splits, the most severe form of split end damage, occur when multiple branches of one strand emerge at once and look like unraveled rope. As more tree splits appear on any single strand, more damage occurs within its cortex; usually indicating you need to trim and deep condition your hair immediately.
Discoloration
The cortex is the thickest layer of hair, responsible for most of its pigment (color) in the hair shaft and much of its elasticity. Therefore, we must take great care in caring for and treating our locks with kindness – such as not overbrushing them too aggressively or subjecting them to too much water or sun.
The cuticle and cortex form the cell membrane complex, which binds hair matrix cells together. This complex is made up of 15nm proteinous delta layers sandwiched by two 5nm lipid beta layers; additionally, it also houses hair’s characteristic odor caused by the release of 18-methyl eicosanoic acid from the outermost delta layers of the cuticle, which then covalently bonds itself onto each keratin strand through 18-methyl eicosanoic acid released by the outer delta layer cuticle releases 18methyl eicosanoic acid covalently linked with its covalently linked keratin. Individual differences exist due to genetics.
Dryness
The cortex contains most of your hair’s pigment (color). It also houses many vital molecules like amino acids, nucleic acid, and minerals – all vulnerable to damage by perms and dyes.
At the core of some thicker hairs lies a layer of soft and thin cells filled with proteins and structural lipids known as the medulla, making some appear whiter than their surrounding cortex.
Like fish scales or roof tiles, a cuticle protects the cortex with scale-like protrusions. A healthy cuticle will limit water movement into and out of the cortex, keeping your hair’s hydration balance and flexibility balanced and intact. When damaged by chemicals or external factors, however, dryness and brittleness occur as a result of chemical processing or UV radiation; this results in split ends where harsh treatment, like hard brushing or too much sun/water exposure, wears away the cuticle altogether leaving just the cortex exposed.
