Chapter 4: Cytomechanics of Hair

The document describes the cytomechanics of hair, explaining that hair is a complex tissue made up of cuticle and cortex cells that function mechanically as a unit. The mechanical properties of hair are determined by the cell membrane complex (CMC), macrofibrils composed of microfibrils or intermediate filaments (IFs), and the surrounding matrix material. The IFs are made up of α-keratin molecules arranged in a specific pattern influenced by their amino acid composition and sequence. Hair's mechanical properties are attributed to various molecular interactions, including mechanical interlocking, hydrophobic effects, hydrogen bonding, Coulombic interactions, and particularly strong disulfide bridges. Mechanical models for hair consider it as a two-component system of microfibril and matrix. A key aspect of hair's mechanical behavior is the transition of microfibril molecules from an α-helical to a β-sheet structure under stress. While hair exhibits negligible longitudinal swelling in water, it experiences significant radial swelling.