Hair Parts

Hair growth is something that we take for granted until we start noticing a tremendous difference in our appearance. Understanding hair loss starts with understanding the many different parts of the hair, and HOW it grows. Hair growth starts while the baby is still in the mother's womb and continues until death. But in between that time a lot can happen and hair growth can stop for several different reasons including:

- the types of shampoo/conditioner used
- blow dryer
- too much sun and wind exposure
- perms, bleach, highlights, and hot oil treatments
- poor nutrition
- illness, condition, or disease

Hair grows everywhere on the human body except on the palms of our hands and the soles of our feet, but many hairs are so fine they're virtually invisible. Hair is made up of a protein called keratin (the same protein in nails) produced in hair follicles in the outer layer of skin; as follicles produce new hair cells, old cells are being pushed out through the surface of the skin at the rate of about six inches a year.

Hair has two separate parts: the root and the hair shaft. The root is the part of the hair located just under the skin surface. The hair follicle houses the entire hair root. The follicle lies below the scalp and produces the hair strand that you see growing out of your head. The follicle is alive.

At the root, the papilla is where all of the action takes place; it is a rich blood and nerve supply that nourishes the hair shaft and produces hair cells. The bulb is a white sack located on the lower part of the hair that covers the papilla.

The hair shaft is what is grows out of the hair follicle and is what we consider to be our "hair". It has three parts; the cuticle, cortex and medulla. The inner layer is called the medulla and may not be present (because of chemical damage).

The next layer is the cortex and the outer layer is the cuticle. The cortex makes up the majority of the hair shaft. There are pigment cells that are distributed throughout the cortex and medulla giving the hair its characteristic color.

The cuticle makes up the largest section of your hair and protects the cortex. The cuticle is formed by tightly packed scales in an overlapping structure similar to roof shingles, which holds your hair together. The cuticle is made of long, molecular chains of amino acids (protein).

The hair shaft is dead, and is simply made up of fragile, dead keratin cells that have no regenerative properties. Hair grows from the follicle at an average rate of half an inch per month. Each hair grows for about four to seven years, after which it enters a "resting phase" and then falls out.

A new hair begins growing in its place anywhere between three weeks and three months later. At any one time, about 90% of the hair on a person's scalp is growing. Each follicle has its own life cycle that can be influenced by age, disease, and a wide variety of other factors.

This life cycle is divided into three phases that each strand of hair must go through during its cycle. These phases are the subject of our next posting, entitled "Hair Life Cycles".



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