Terminal hairs on the head are lubricated by a natural oil (sebum) produced by the sebaceous glands of the follicles. The amount of natural oil your glands produce is mostly determined by your genetic inheritance. However, for men and women, glands tend to produce more oil when levels of their hormones (androgens) are high. In many teenagers, a massive surge in hormone levels leads to raised grease production. This results in a tendency to greasy hair, which many young people would be well familiarized with. The good news is that most of them outgrow it.
Structure of the hair shaft
Smooth, glossy hair possess a much more complicated structure than one might imagine. Each one is comparable to a tree: all its moisture lies in its center, behind a tough outer layer of protective bark. If the 'bark' of the hair is well maintained, the whole hair remains in good condition but if the 'bark' is stripped off to expose the centre the hair may break.
The center part of the hair, called the cortex, makes up most of the hair shaft. It is the cortex that gives hair its special qualities such as elasticity and curl. It (cortex) is packed with strands of keratin, lying along the length of the hair. These keratin fibers are made of the low sulphur keratins, and are compressed into bundles of larger fibers. These are held together by a mass of sulphur rich keratins, the matrix. The fiber matrix combination is extremely strong and resists stretching and other strains such as twisting, much as does the glass fiber resin mixture from which many boats are built.