The Hair structure and its growth stages
The hair structure is simple, but its function is important in a person’s social life. Hair consists solid proteins called keratin. Hair follicle fixes each hair to the skin. The hair bulb forms the base of hair follicle and it contains cells in division, which grow to make the hair shaft that appears outside the skin.
Blood vessels nourish the hair bulb cells, and transport hormones that control hair growth and its structure in different stages of life.
What is hair made of?
Your hair grows from hair bulbs present inside the skin. The part of the hair inside the follicle (under the skin surface) is called hair root, while the visible part is the hair body or shaft. At the base of the root there is hair bulbs in which absorb nutrients from blood and form new cells.
The hair follicle contains also:
- Dermal papilla: it is a conic nipple present in the base of follicle. It nourishes the hair bulb with blood, subsequently with nutrients. The dermal papilla is responsible of taking the vital nutrients for a healthy hair from blood and improving hair nutrition. Dermal papillae contain also Androgen receptors. Androgen causes hair atrophy. It is the hormone that controls hair growth as it can cause thinning hair and hair loss too.
- Sebaceous glands: it secretes oily matter to lubricate hair and keep it healthy and glimmering.
- Arrector Pili muscle: (a little muscle that surrounds the follicle) it responds to stimulus (fear or cold) making the follicle shrink and the hair stands erect. During that, the bulb takes nutrients from the dermal papilla to form new cells.
When these cells move up through the hair root, they differentiate and get filled with fibers and lose their nuclei. They are no more alive.
The hair shaft is composed of:
- A thin outer protective colorless layer to protect the cortex.
- Cortex, it gives the hair rigidity, color and texture
- Medulla (present in the permanent hair) between its cells exist lot of air vacuums.
In fact, your hair is composed of 91% proteins, and long peptide chains. These chains contained in fibers of the cortex. The amino acids of these chains consist of carbon, oxygen, hydrogen, nitrogen and sulfur (which are the main components of skin and nails).
We can clearly notice the essential role of proteins in hair structure and the importance of insuring the daily needs of protein to keep a healthy and strong hair.
How many hairs in the human head?
- In average, each person’s head contains about 100.000 hair bulb. Some people may have 150.000 or more.
- In child’s head, there are about 1100 bulb for each 1 cm². This number decreases when reaching 25 years old and becomes around 600, but that depends on the physical state of a person.
- At the age between 30 and 50, the number of hair bulbs decreases to more than 250-300 bulb for each cm², then, a slight hair loss starts while aging.
- Each bulb gives about 20 new hairs. Each new hair grows for several years and may reach more than 1 meter.
- Each hair falls at the end, and is replaced by a new one.
And now let us talk about hair growth cycle:
It is very important to understand hair growth cycle and the many problems that may face your hair. Hair growth cycle consists three stages: Anagen, Catagen and Telogen.
Anagen (growing phase):
Your hair grows around 1.25 cm per month, faster at summer than at winter. Anagen or growing phase lasts about 3-5 years, so the average of the total hair length is from 45 cm to 76 cm. The growing phase is longer in the Asian race and can last to 7 years, the hair length may reach 1 meter.
Catagen (regressing phase):
At the end of growing phase, your hair starts regressing in a transitional phase that last 10 days approximately.
Telogen (resting phase):
Finally, your hair starts telogen, a resting phase in which hair shedding occurs. After that, the hair follicles stay inactive for 3 months, then restart the cycle. Every single follicle starts growth cycle in different times, if the opposite, your hair would fall all at once. Instead, you will lose some hairs a day (80 hairs in a healthy head hair).
Hair loss is a problem occurs during growth when the cycle stops. It may be affected by some conditions as metabolism disorders and malnutrition.