Hair largely serves as a sensory device. The base of each and every hair has many sensitive nerve fibers which send signals whenever the exterior portion of the hair is stimulated through touch. Hair also protects the body from debris. Eyebrows and eyelashes catch debris before it can irritate the eye, and nostril hair keeps debris out by first ensnaring it, and then triggering a sneeze.
All hair has many different structures that enable it to grow hair. The most important ones are:
The shape of the hair follicle determines the shape of the accompanying hair. A perfectly ovular hair follicle will produce straight hair. In contrast, a slightly less circular follicle will produce wavy hair, and a more narrow follicle is what produces hair that is curvy and kinky. There is no distinct advantage to having a particularly shaped hair follicles, though each hair type comes with its own unique characteristics.
The hair follicle plays an active role during the three stages of a hair’s lifecycle:
The androgen known has DHT can reduce the ability to produce healthy new hair. Over time, DHT can have a shrinking effect on the diameter of the follicle itself. With a reduced diameter, it will produce thin, brittle hair that can shed easily. While this may impact the length of the anagen and telogen phases at first, eventually the follicular structure may be too narrow to develop hair at all. This process is known as miniaturization. Miniaturization can be addressed with medications such as Rogaine and Propecia.