All hair follicles are formed in utero by 22 weeks. There are about five million hair follicles, about one million of those on the head and scalp, and 100,000 on the rest of the body. Hair follicles do not continue to grow during life. As we age, the number of hair follicles decreases as we stretch and grow.
Hair Structure: Hair Follicle
A piece of hair is one of the body’s most complicated structures. Hair has two separate structures: the hair follicle below the skin and the hair shaft above the skin. The hair follicle holds the hair in place and is where hair starts to grow. This stocking-like structure begins in the epidermis or top layer and extends out to the second layer of skin, or the dermis. A piece of tissue called the papilla is at the bottom of the hair follicle. This contains tiny blood vessels, also called capillaries. These nourish the hair root to keep hair growing and healthy. The hair follicle also contains the germinal matrix that produces new hairs. The bud of the follicle is a rounded structure found deep in the skin at the root of the hair. This surrounds the germinal matrix and the papilla. Several types of stem cells here turn into specialized cells that can renew themselves over time. The follicle is lined by an inner and outer sheath that protects and shapes the developing hair. The inner sheath follows the hair and goes to just before the opening of the oil gland, called the sebaceous gland. The sebaceous gland creates sebum, an oil that acts as the body's natural conditioner. Sebum is produced more during puberty and decreases with age. The outer sheath grows all the way up to the gland. Attached to the outer sheath is the arrector pilli muscle. This tiny bundle of muscle fiber causes hair to stand up when the muscle contracts. Hello goosebumps!
Hair Structure: Hair Shaft
Once the hair grows beyond the surface of the skin, the cells are no longer living. It is made up of keratin, a hardening protein that has three layers.
The inner layer, called the medulla, that may or may not be present.
The middle layer, called the cortex makes up most of the hair shaft. Both the medulla and cortex contain pigment cells that give hair color. The outer layer, called the cuticle that is formed by scales packed tightly together in an overlapping structure that looks like the shingles of a roof.
The Growth Cycle
Hair can be in one of three growth stages.
Anagen Phase: Stage 1 (2-5 years & 30-45 days)
This is the growth phase of hair, and hair can last several years in this stage. New hair will push old hair out of the follicle. The cells in the root of hair divide rapidly, resulting in the formation of new hair. Scalp hair can grow 1 to 1.5 cm every 28 days and stays in the active growth phase for 2-5 years. While eyelash, eyebrow, leg, arm, and nose hair remain in this phase for 30-45 days.
Catagen Phase: Stage 2 (3-6 weeks)
The catgen phase is a transitional phase that lasts 3-6 weeks. During this time, the follicles prepare for rest. About 3% of all scalp hair is in this phase at any time. Growth stops, hair follicles shrink, and portions of the hair follicles collapse and form the club hair.
Telogen Phase: Stage 3 (3-5 months)
This is the resting phase, and it can last for about 3-5 months. About 10-15% of hair is in the phase at any time. During this phase, the hair follicle is at rest, and the club hair is fully formed.
Exogen Phase: Stage 4
This is the shedding phase. During this time, the older hairs have finished their life cycle and will push out to make way for new growth. You can shed 25-100 telogen hairs every day during this cycle.
What is hair?
Hair is made of the protein keratin. This keratin is formed by amino acids that are sourced from the foods we eat. This protein is also found in fingernails, toenails, and skin.
Nutrients are essential building blocks for keratin protein and play a crucial part in hair health. The following nutrients are the most important for hair health.
Biotin is a water-soluble form of vitamin B. It helps to support hair growth and defend hair from environmental damage. It metabolizes amino acids from food. This helps keratin form in hair.
Iron supports hair growth as it helps to form red blood cells that deliver oxygen and nutrients to hair follicles.
Vitamin C is a powerful antioxidant that helps to protect hair follicles from damaging free radicals.
Niacin or vitamin B3 helps to repair the DNA in hair follicle cells.
Selenium & Zinc both are important for scalp protection.
Omega-3 helps with free radicals and pollutants. It infuses the hair with life, making it shinier and stronger. It helps in new hair growth by improving blood circulation in the scalp.
Vitamins A, B, C, and E all aid in cell growth and free radical prevention and nourish the follicles that stimulate growth.
Hormones & Organs involved:
Hormones play a significant role in hair production and are a complex interaction. Androgens are key regulators of hair growth. Melatonin, prolactin, melanocyte-stimulating hormone (MSH), thyroid hormones, cortisol, testosterone, and estrogens are also involved. Balanced hormones regulate the duration of various phases of the hair development cycle.
Androgens such as testosterone and dihydrotestosterone (DHT) bind to androgen receptors in hair follicles and can help regulate growth cycles. Estrogens help stimulate hair development by extending the anagen (growth) phase, increasing the number of active hair follicles, and keeping hair growing. Thyroid hormones such as T3 and T4 are essential for controlling the body's metabolism, which includes hair follicle growth. High cortisol levels can disrupt the hair growth cycle and cause hair to enter the telogen (resting) phase prematurely. Insulin and isulin-like growth factor-1 (IGF-1) can keep testosterone in check, helping with loss and thinning. Progesterone can alter the texture and volume of hair.
Aging can change hormones, resulting in changes in hair, including texture and location. Some medications can also affect the balance of hormones, resulting in an impact on hair growth.
According to traditional Chinese medicine, the health of the kidney and the liver play a significant role in the growth and maintenance of hair. The liver is the largest organ in the body, and because it breaks down food and creates proteins, it can affect the hair. Bile plays a vital role by breaking down nutrients and transporting them. The liver also produces hormones and proteins that are essential to hair growth.
Fun Hair Facts:
- A single strand of hair can support up to 6.5 lbs of weight.
- Each strand of hair can contain traces of 14 different minerals, including gold. Hair contains information about everything that has been in your bloodstream, including medicine, drugs, minerals, and vitamins.
- The most common hair color is black, and the rarest is red, which is found in 1% of the population.
- Hair is the fastest-growing tissue in the body, second to bone marrow.
Nutrition Support:
- Eggs
- Citrus
- Berries
- Bananas
- Chickpeas
- Strawberries
- Spinach
- Sweet Potatoes
- Avocados
- Brown Rice
- Oats
- Lean Meat
- Fish
- Nuts
- Seeds
- Pumpkin Seed Oil
- Olive Oil
- Sweet Peppers
- Oysters
- Meat
- Omegas
- Bone Broth
- Collagen
- Iron
- Zinc
- Biotin
- Iodine
- Folate
- Copper
- Selenium
- N-Acetyl-Cysteine
- Vitamins: B, E, C, D
Lifestyle Support:
- Reduce Stress
- Exercise
- Scalp Massage
- Use satin pillowcases
- Don’t brush your hair when wet
- Avoid heat styling
- Clarify your hair once a month
- Use hair masks regularly
- Wash and rinse hair in cool water
- Avoid smoking
- Use hair moisturizing oils
Herbal Friends of the Hair:
- Fo-ti
- Rosemary
- Horsetail
- Stinging Nettle
- Fenugreek
- Lavender
- Centella Asiatica
- Holy Basil
- Burdock
- Curry Leaves
- Hibiscus
- Spikenard
- Neem
- Water Hyssop
