Types of Hair
Morphologically, there are 3 types of hair growing on the human body. These are vellus hairs, terminal hairs and intermediate hairs.
Vellus hairs are short hairs of a centimeter or two long. A vellus hair contains little or no pigment, and thus, is colorless. Vellus hair follicles do not have adjacent sebaceous glands. At the same time, their shaft does not have a melanin layer. Vellus hairs are fine and soft, and are not cosmetically important.
Terminal hairs are long hairs that grow on the scalp and in many people on the body. They are produced by hair follicles with adjacent sebaceous glands. Terminal hairs have large, darkly pigmented hair fibers that have a medulla at the innermost part.
An intermediate hair shows the characteristics of both vellus hairs and terminal hairs. Intermediate hairs have a medulla and contain a moderate amount of pigment, less than that found in the terminal hair type. During the balding process terminal hair follicles and intermediate hair follicles change in such a way that they no longer produce terminal hairs. In these areas, hair follicles grow vellus hairs rather than terminal hairs.