At birth, your body already had all the hair follicles it would ever have. They may change in size, but you will not develop new ones. The average Caucasian has about five million hairs on his body and only 100,000 to 150,000 of these grow on the head. Blonds tend to have more head hair and redheads have a little less than average, says hairlosshelp.com. Each hair grows on its own cycle, so that you are losing a portion of your hair at all times but new hair is growing.
Anatomy
A hair's anatomy has two primary parts, the follicle and the shaft. The follicle is a pocket-like structure below the surface of the skin that provides a supporting structure and nourishment for the hair shaft. It receives oils from the surrounding sebaceous glands and distributes this oil along the hair shaft. The hair root fits into the follicle. Only one hair grows in each follicle. Melanocytes--cells that produce pigment--grow along the edges of the follicles and release melanin directly into the hair shaft.
Anagen Stage
Hair grows in three stages, the first of which is the anagen stage. This is the growth period for the hair shaft and it normally lasts between two and eight years. During this phase, the follicle moves deeper into the skin layers to get more blood to nourish the shaft. The cells at the root of the shaft divide rapidly. They convert to keratin as they push above the skin line. Hair normally grows at a rate of about one-half inch per month.
Catagen Stage
When a hair's growing phase ends, it enters a brief transitional phase--the catagen stage--which lasts two to four weeks. During this time, the follicle undergoes significant changes. It shrinks to approximately one-sixth its size during the anagen phase, the lower portion disintegrates and it detaches from its blood supply. The hair shaft begins to move up through the skin layers as the follicle disintegrates. At any one time, 3 percent of your hair is in this phase.
Telogen Stage
After the transitional phase, the follicle enters a resting phase--the telogen stage--which lasts two to four months. The shaft remains attached to the follicle but it no longer has nourishment, so it does not grow. When this stage is complete, the hair will fall out and the follicle will re-enter the anagen stage and being to grow a replacement hair. Approximately 10 to 15 percent of your hair is in this stage at any given time and the loss of 50 to 100 strands of hair per day is quite normal.
Individuals
All hair grows through the same three-stage process, but the length of each stage differs for each person. Depending on the length of your anagen stage, your hair may grow to a total length of 12 to 48 inches if you don't cut it. If you have difficulty growing your hair long, it's probably because you have a short anagen stage. Hair thinning stems from a short anagen stage and an unusually long telogen stage. This eventually causes the hair follicles to shut down completely. Non-genetic factors, such as chemotherapy, medication, thyroid disease and hormonal changes may cause temporary or permanent disruption to the hair growth cycle.
Member Comments