Hair growth is one of the most amazing aspects of the human body. And, although you have thousands of hairs all over your body, you probably think nothing of it. Did you know that once a fetus is about 22 weeks old he has developed five million follicles all over his body? And, that is all he will ever have too. Now, what else can we learn about the biology of hair?
What’s It Made Of?
The anatomy of a strand of hair is amazing. First, there is the follicle which is actually embedded into the skin. The hairs grow from the follicle through a shaft. The papilla lies at the base of the follicle as one of the many layers of the follicle. Next, capillaries help to connect the papilla to the blood supply. These surround the bottom of the hair called the bulb.
There are two sheaths that are in place to protect the hair shaft from being damaged surrounding the follicle. In one of them, runs next to the hair shaft and stops at the sebaceous gland. The other, the outer sheath, runs from the glad and stops at the erector pili muscle.
Keratin is dead protein cells that are what make up the hair shaft. The inside layer of them is the medulla. The second is the cortex and it provides the most hair shaft. Hair color is determined in this layer. The cuticle is the outside most layer and it has a series of overlapping cells. The luster of the hair comes from this layer.
How Growth Happens
Hair growth happens in three main stages. Did you know that your hair will only grow .3 to .4 millimeters per day? That is only six inches per year! Although it seems like it grows much more it really does not.
The Stages:
- Catagen Phase: This is the transition phase. It lasts about two to three weeks. There is no hair growth now, as the goal is for the outer portion of the hair root sheath to shrink and then attach itself to the root.
- Telogen Phase: The resting period. About 15% of your hair is in this stage at any given time. It takes about 100 days for the scalp hair and much longer for the body hair to go through this stage.
- Anagen Phase: Hair cells are dividing and new hair growth is happening. It can last for as long as two to six years! Do you have trouble growing your hair long? This happens because your hair in this stage does not last nearly this long.
What Can Go Wrong?
There are several hair abnormalities that can happen. These hair disorders can strike just about anyone, but are in most cases rare. One, hirsutism is when individuals, mostly women, have excessive hair growth that is in odd places. For most women, the hair is darker and coarser than it should be. It can occur on the face, chest or the areola.
Another condition known as hypertrichosis is very rare and happens when individuals suffer from hair that grows thickly in areas of the body that it normally would not.
These conditions can be treated fairly well if help is sought out. Hair growth, while a very common and seemingly ordinary thing, actually is much more complex than people imagine. But, understanding how it works can help you to understand how to rid your body of unwanted hair.