Issue link: https://www.ahpindiestylist.com/i/1547346
50 AHP Indie Stylist Volume 7 Issue 2 GETTY IMAGES HAIR ANATOMY: KNOWING THE LAY OF THE LAND e hair strand is already dead by the time it clears the scalp. e only living portion of hair is tucked inside the follicle, where matrix cells divide, fi ll with keratin, and are pushed upward and outward in a process called keratinization. 1 By the time a hair strand is visible to us, it has no blood supply, no nerve connection, and no cellular machinery with which to heal itself. is is the fi rst principle of hair recovery, and it's the one that controls everything else. Hair can't regenerate the way skin can. What we call "repair" is really patching, reinforcement, protection, and intelligent management of a nonliving fi ber. Your ability to reach for the right tools and master this process is what your clients truly pay for. Our hair fi bers have a complex and elegant architecture. 2 e outermost layer, the cuticle, consists of 5–10 overlapping layers of fl attened, translucent cells arranged like shingles on a roof, all pointing down toward the tip. A thin lipid layer, called the F-layer, coats the cuticle, waterproofs the hair fi ber, and gives it natural slip. e cuticle is the strand's fi rst line of defense against damage. It controls how much water enters and leaves the cortex beneath it. e cortex is the bulk of the fi ber. It's a dense bundle of keratin proteins twisted into progressively larger cables and held together by diff erent types of chemical bonds: • Disulfide bonds, the strong covalent links between sulfur atoms in the amino acid cystine, give hair its permanent shape and much of its strength. • Hydrogen bonds and salt bonds are weaker and temporary. ey break with water and heat, which is why hair can be reshaped when wet and why humidity undoes a blowout. e strand's shape also tells us something about its natural strength. Straighter strands have a round, more even cross section, and that geometry imparts natural strength. However, curly and coiled strands have an elliptical, irregular, or narrowed cross section, which can compromise their natural strength. Instead of running in one direction, coily strands also change direction constantly along their length. Every twist, turn, and reversal is a potential weak point where the cuticle li s slightly and mechanical stress can lead to breakage. Clients with highly textured hair also tend to have less cuticle-layering protection to work with. e shape of the strands also means that natural oils have diffi culty making the journey from root to tip, and it's trickier to apply protective conditioning products evenly. ese fragile strands appear tough but are more prone to breakage than other types. THE ANATOMY OF A DAMAGED STRAND When hair is damaged, the lipid layer strips away fi rst, so the strand loses its water resistance. Cuticle scales chip, crack, and li , causing the surface to become rough and porous. Once the cuticle is breached, the cortex loses protein fragments every time the hair is washed, and the strand's ability to hold moisture collapses. A worn cuticle is a porous cuticle. Porous hair drinks in water quickly and loses it just as fast. It swells excessively with every wash, and tangles because its raised scales snag against neighboring strands. Repeated swelling and contraction produce the hair's own fatigue damage in the cuticle, so porosity becomes self-accelerating. Le unmanaged, the fi ber thins, splits, and fi nally fractures. Damaged hair Healthy hair