The Structure and Growth of Hair

As mammals, we have hair almost everywhere on our bodies. Some is unnoticeable because it is soft, fine vellus hair, while other places on our body have thick, noticeable hair called terminal hair. This protein is an important part of regulating our bodies' temperatures, but it can also be unsightly or embarrassing and need removal.

We have three types of hair: lanugo, vellus, and terminal. Lanugo is only present on our bodies while we are still in the womb. Vellus hair is the nearly unnoticeable that covers our bodies, and at the onset of puberty, some of this hair turns into the thicker, darker terminal hair. All three types of hair are composed of a protein called keratin, which is the same material that composes our nails and the outer layer of skin.

The main difference between vellus and terminal hair is that the former is made up of two layers, while the latter has three. Terminal has an inner core, called the medulla. Both of the types have a layer called the cortex, which is in charge of the strength and color. Lastly, the outer surface for both terminal and vellus is called the cuticle. It is thin and colorless and serves mainly to protect the cortex.

Under the surface of the skin, there is a complex that is in charge of growing the hairs. The root of the hair itself is held in the follicle, which is where the components necessary for hair growth come together. Connected to the follicle is the dermal papilla, which contains blood vessels that bring oxygen and nutrients to the cells that produce hair. Additionally, hormones are carried in to the dermal papilla and interpreted as instructions for growth. For example, androgen is a male hormone that may signal the production of terminal hair on the face.

Contrary to what you may think, hair is not constantly growing. It actually has three distinct phases that together make up one growth cycle. The three phases are constantly repeated, which means that your hair is always going through one growth cycle after another. First, hair spends most of its time in the anagen phase, or growth phase. After 2-6 years, it transitions into catagen phase for 1-2 weeks. During this time, the follicle shrinks and separates from the dermal papilla. Lastly, the telogen phase is the resting period. Hair is in this for 5-6 weeks.

Each follicle is independent from the others as to when it enters each growth cycle. This is why laser hair removal requires that you go in for treatment several times, since hair must be targeted during the growth phase. However, once you get laser treatment and all your follicles are zapped, you can be hair-free forever.

For more information regarding the laser hair removal process, talk to the cosmetic dermatologist Dr. Zimmet of Zimmet Vein & Dermatology today.