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Fig. 1: Undamaged hair |
Tonya McKay writes:
As a polymer scientist with a love for biological structures, I find hair and skin to be extremely fascinating systems. Human hair is an intricate composite structure comprised of keratin proteins, lipids, polysaccharides, water and pigment particles. All of the individual components are complex and perform very specific functions. Those of us with curly hair are concerned a lot about our hair’s texture and porosity (a popular buzz word of late). These two factors are primarily based upon the structure of the cuticle — the outer layer of our hair.
The scanning electron microscope image in Figure 1 shows highly magnified detail of the exterior surface of a strand of human hair. The external layer is called the cuticle, and is much like bark on a tree. Both the cuticle layer and tree bark are made up of many smaller, individual pieces (called scales when referring to the cuticle) that work together as one overall unit to perform a function. The job of the cuticle is to provide protection to the hair shaft from mechanical and thermal damage, while allowing moisture in and out as needed. The cuticle structure is an amazing work of nature, because it is strong, yet flexible, and is made up of many pieces, which allows it to act as a seal to protect the inner cortex of the hair, and yet also allows it to be permeable, or porous.
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