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Hair Growth Cycle

How Hair Grows

hair growthBefore we discuss alopecia or hair loss treatment options, we must first learn about the stages of hair growth. On average, a person typically has between 100,000 and 150,000 hairs on their head at a given time. These hairs are known as “terminal hairs.”

As humans advance in age, their ability to reproduce terminal hairs is diminished and those terminal hairs are replaced with vellus hairs; which is often referred to as “baby fuzz” because it mimics the texture of a newborn’s hair. Alopecia results when the 75 to 100 dead or damaged hairs that we lose on a daily basis are not regrown.

The 3 Phases of the Hair Growth Cycle

Phase One: Active Growth (Anagen)

Anagen is the active phase of the hair growth. The cells in the root of the hair are dividing rapidly. A new hair is formed and pushes the club hair (a hair that has stopped growing or is no longer in the anagen phase) up the follicle and eventually out.  During this phase the hair grows about 1 cm every 28 days. Scalp hair stays in this active phase of growth for two to nine years. As the anagen phase shortens, hair will become noticeably finer and thinner, and with less pigment.

The hair on the arms, legs, eyelashes, and eyebrows have a very short active growth phase of about 30 to 45 days, explaining why they are so much shorter than scalp hair.

Phase Two: Regressive Phase (Catagen)

The catagen phase, which is also known as the hair loss phase, typically lasts three to four weeks and can be associated with brushing or shampooing. In this phase, dead or damaged hairs are lost to make way for new hair growth. Growth stops and the outer root sheath shrinks and attaches to the root of the hair. This is the formation of what is known as a club hair. About 3% of all hairs are in this phase ant any time.

Phase Three: Resting Phase (Telogen)

Telogen is the resting phase because the hair is not growing or falling out. This usually accounts for 6% to 8% of all hairs. This phase lasts for about 100 days for hairs on the scalp and longer for hairs on the eyebrow, eyelash, arm, and leg. During this phase, the hair follicle is completely at rest and the club hair is completely formed. Pulling out a hair in this phase will reveal a solid, hard, dry, white material at the root. About 25 to 100 telogen hairs are shed normally each day.

Hair Restoration Definitions

Hair Follicles – Hair has two distinct structures – first, the follicle itself, which resides in the skin, and second, the shaft, which is what is visible above the scalp.

Hair Shafts – The hair shaft is made of a hard protein called keratin and is made in three layers. This protein is actually dead, so the hair that you see is not a living structure.

Schedule a consultation with Dr. Serrão to learn more about the Hair Restoration Program at Serrao Rejuvenation Center.  Contact us or Call 407.896.3772 today!

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