The hair composition or physical thickness and length of hair depends on what type of hair it is. Vellus hair is the fine fuzz type of hair that’s often called peach fuzz. It's very fine and colourless and often almost invisible to the naked eye.
The average Caucasian person has 5 million hairs of which 100,000 – 150,000 are on the head. Blondes not only have more fun, they also have more hair, about 140,000 more than average, Brunettes have slightly higher than average hair about 105,000 hairs, and redheads have a little less than average about 90,000 hairs. African Americans have about 108,000 strands.
Hair that is dark and very visible is known as Terminal hair. Terminal hair is the hair that we refer to when we talk about hair. Whether a hair is a fine Vellus hair or a thick dark hair depends entirely on the follicle that is producing the hair. In balding men thick terminal hair is often replaced by fine Vellus hair. This is the result of the hair follicle being miniaturised which means shrinking of the hair follicle and a lack of oxygen to the dermal papilla which carries nourishment to the hair follicles. In order to grow healthy hair one must have both of these functioning properly.
Here are some terms that may be useful to know when you talk with a Trichologist. Hair is composed of Keratin, a special protein that also produces our fingernails and toenails and forms the protective outer layer of our skin. Each strand of hair consists of three concentric layers, the cuticle, the cortex and the medulla.
The outer layer is called the cuticle and is thin and colourless, its job is to protect the thicker cortex which contains the melanin. Melanin is responsible for the colour of your hair and the actual colour depends on what kind of melanin you have. There are two kinds, Eumelanin which creates brown or black hair, and Pheomelanin which makes hair appear red. Blonde hair is a result of very low amounts of melanin, the shade of the blonde again depends upon which type of melanin you have. Grey hair is a result of a lack of melanin, which is often caused by age, but can also be caused by stress and illness. The innermost layer of hair is called the medulla and reflects light giving hair the various colour tones it has. That’s why hair colour looks a lot different in sunlight than it does in the shade.
Whether you have straight or curly hair depends on the shape of the cortex. If the cross section of the cortex is round you will have straight hair, if the cortex is oval shaped you will have curly or wavy hair.