Hair and its Anatomy
It may come to a surprise to many of you that even a strand of hair is an amazing complex part of your body. A human’s hair growth starts inside the womb as a developing fetus. By the time a developing fetus reaches 22 weeks old, there are already 5 million follicles on the body. Interestingly enough, that is all of the follicles that will ever develop regardless of how long we live.
Hair’s Anatomy
Hair consists of a follicle in the skin that holds the shaft of hair that appears on the body. The follicle itself consists of multiple layers with each layer having a specific function. In the base of the follicle we find the papilla. The papilla is connected to the capillaries that supply blood to the cells around the bulb (the bottom part of the hair strand).
The follicle is surrounded by an inner and an outer sheath that helps the hair shaft to grow in the right direction and protects it from damage. Inner sheaths run next to the hair shaft, ending in the oil gland (sebaceous). Outer sheaths run into the glands aswell, but the end in the erector pili muscle. The erector pili muscle is the muscle that causes the hair to stand on end when the muscle contracts.Each hair shaft has three layers that is made up of keratin which is dead protein cells. The innermost layer, known as the medulla, is not always present in every hair shaft. The bulk of the hair shaft is provided by the second layer, called the cortex. The hair color is mostly determined by the pigmentation contained in this layer. The outermost layer of hair shafts is known as cuticles.Cuticles are comprised of a series of overlapping cells. The cuticle also gives luster and sheen to the hair.
Growing Hair
Scalp hair grows at an average rate of only 0.3mm to 0.4mm per day, adding to a mere six inches per year.
The three stages of hair growth.
Catagen Phase
This phase is the transitional phase and it runs about two or three weeks. At any given time approximately 3% of your hair is in this phase. During this period there is no hair growth and the out portion of the hair root sheath then shrinks and attaches itself to the root.
The Telogen Phase
This phase, known as the “resting period” is experienced by approximately 15% of your hair. The Telogen phase for scalp hair lasts for around 100 days and significantly longer for any other hair on your body.
Anagen Phase
The anagen phase is a period of activity in which the hair cells are dividing and new hair starts growing. This phase can last for as long as two to six years. People who have trouble growing their hair long usually experience shorter growth periods.
Hair Growth Disorders
Humans are mostly affected by two hair growth disorders. Hirsutism is the most common condition that affects mostly females. The condition is known for excessive thick and dark hair growth in in typical male areas. The areas may include the face, chest, areolae or the area around the nipple. The other common condition is called Hypertrichosis and it causes excessive hair growth in areas where visible hair is not normally present. Both Hirsutism and Hypertrichosis can be treated.
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