Fibril and hence the whole muscle. Elastin is a fibrous protein common in various soft tissues, like skin, blood vessels and lung tissue. Each monomer connects with each other, forming a 3D network, with ability to endure over 200% strain before deformation. Keratin is a structural protein mainly found in hair, nails, hooves, horns, quills. Basically keratin is formed by polypeptide chains, which coil into α-helices with sulfur cross-links or bond into β-sheets linked by hydrogen bonding. β-keratin, which is tougher than α-conformation, is more common in birds and reptiles. Resilin is an elastomeric insect protein, consisting of both α-helices and
Facial hair developing facial hair, especially after menopause, though typically significantly less than men. Men may style their facial hair into beards, moustaches, goatees or sideburns; others completely shave their facial hair. The term "whiskers", when used to refer to human facial hair, indicates the hair on the chin and cheeks. The moustache forms its own stage in the development of facial hair in adolescent males. Facial hair in males does not always appear in a specific order during puberty and varies among some individuals but may follow this process: Depending on the periods and countries, facial hair was prohibited in the