Understanding Hair Anatomy & Hair Growth Cycle

Hair plays a vital role in enhancing the personality of a human. As the hair is the first noticeable part of beauty for women as well as men. The scalp and hair conditions also have a more psychological impact on human societies. Even minor changes in hairs like greying of hair, early hair fall affect the self-confidence and self-esteem of an individual.

Acharya Charka considered Hair as Mala (Waste product)/ by-product of Asthi Dhatu (Bone), while Sharngdhara thinks of it as a Updhathu (tissue) of Asthi as are the nails and teeth, making all of these tissues intimately connected.

Before we talk about various hair and scalp concerns, it is important to understand the hair and scalp anatomy.

Hair Anatomy

Your hair structure can be divided into two parts:

  1. The structure inside the follicle.
  2. The structure of the hair shaft is present above the epidermis and is the visible part of the hair.
Structure Inside Follicle

A. Hair Bulb: It is the lowest part of your hair strand, which lies inside the follicle. The club-shape of the hair bulb helps it to get locked by the dermal papilla.

B. Dermal Papilla: It is the cone-shaped elevation which is present at the base of your hair follicle. It fits into the hair bulb and holds it. Dermal papilla is connected with the blood vessels.

C. Arrector Pili Muscle: It is an involuntary muscle present at the base of the hair follicle. You get goosebumps when arrector pili contracts.

D. Sebaceous Glands: These are the oil glands that are connected to the hair follicles. Sebaceous glands secrete sebum for your hair.

Structure Of Hair Shaft

A. Cuticle: It is the outermost layer of your hair strand. It acts as a protecting layer to the inner hair structure. A strong and integrated cuticle layer imparts shine and smoothness to your hair.

B. Cortex: It is the middle layer of the hair strand. The protein present in the cortex is responsible for the elasticity and color of your hair.

C. Medulla: It is the innermost layer in the hair strand. In general, it exists only in thick and coarse hairs. The purpose of the medulla has not been identified yet.

Hair Physiology   

The different layers of the visible part of hair (shaft) are due to the alterations in the morphology and structure of matrix cells of the bulb. In the matrix cells takes place protein synthesis -especially Keratin synthesis- which contributes to the strength and endurance of the hair shaft and to nail configuration as well. Keratin also lies in the skin. Keratin is a group of proteins that contain sulfur and is being produced in the keratogenous zone of the root. Hair consists of proteins (65% – 95%), lipids (1% – 9%), trace elements, polysaccharides, and water.

Phases of Hair Growth

A normal human being has approximately 1 million hair follicles on his body, of which 1 lacks hairs on the scalp. Hair growth happens in a cyclical process in your hair follicles. The cycle consists of four phases-anagen (growth), catagen (regression/transition), telogen (rest) and exogen (shedding). The whole cycle lasts for a few years for each of your hair strands on the scalp.

As per the ancient Ayurvedic wisdom, every human is comprised of three vital life energies called doshas namely Vata, Pitta, and Kapha. While the unique constitution levels of these three doshas determine the unique Prakruti of the person, it is believed that each dosha has a major influence on the Prakruti for a specific period in the lifetime of an individual.

Kapha dosha is believed to have a dominant role from childhood to adolescence, ie. Until the age of 16 years. This can be considered as the Kapha Kala of life. During adolescence or Kapha Kala, your hair will have the most convenient ambiance to remain healthy and strong.

Pitta dosha is believed to have a major role from adolescence to old age. i.e, until a person reaches 50 yrs of age, which can be considered as Pitta Kala of life.  Similarly, Vata dosha plays a predominant role in old age, i.e, from 50 yrs to the end of the lifetime, called Vata Kala. Most of the hair-related problems and hair loss are observed during Pitta and Vata Kala of human life.

A person can also have imbalanced Kapha dosha, which causes conditions like severe dandruff, hair loss, and other scalp infections. Now, let’s understand the different stages of hair growth and their correlation with Ayurvedic Kalas.

Hair growth happens in a cyclical process in your hair follicles. The cycle consists of four phases-

  • The growth phase (Anagen)
  • The regression/transition phase (Catagen)
  • The resting phase (Telogen)
  • The shedding phase (Exogen)
    Anatomical training poster. Hair growth phase step by step. Stages of the hair growth cycle. Anagen, telogen, catagen. Skin anatomy. Cross-section of the skin layers. Medical vector illustration
The whole cycle lasts for a few years for each of your hair strands on the scalp. In a normal healthy person’s scalp, about 85% of the hair follicles are actively growing hair (anagen hair) and about 15% are resting hair (telogen hair). A few hairs may also be in catagen. A hair follicle usually grows anagen hair for 4 years or so, then rests for about 4 months.  A new anagen hair begins to grow under the resting telogen hair and pushes it out.

The Anagen Phase – Growth Phase

The phase in which hair starts growing from the follicle root is called the Anagen phase. During anagen, the stem cells of the dermal papilla multiply to produce hair protein and fibers. This is a period of epithelial proliferation, in which bulb matrix cells undergo mitosis and proliferation to form the hair shaft.

Anagen hairs are fully pigmented and attached to the dermal papilla. They have long, indented roots covered with inner and outer root sheaths. Body hair is shorter than scalp hair due to a shorter anagen phase. 

The span of the anagen phase lasts from 2-7 years depending upon your Prakriti (genetics) and various internal and external factors, while it determines the length of that hair strand. Hair grows approximately 10-15cm per year. In general, the length of any human being’s hair is unlikely to grow more than one meter.

The duration of anagen varies depending on the body site, age, nutrition, and hormones. Stress and poor diet can shorten anagen.  Estrogen prolongs anagen. In male and female patterns of alopecia, dihydrotestosterone shortens the anagen phase and causes miniaturization of the hair follicles.

In Ayurvedic terms, the anagen phase can be correlated to Kapha Kala during which your hair grows steadily for a longer period. As you age, the transition of Kapha and Pitta Kala occurs, which results in a decrease in the span of the anagen phase.

Anagen Effluvium: Anagen effluvium is an abnormal, rapid loss of hair. Any insult that impairs mitosis of hair follicle keratinocytes can cause anagen effluvium. Disruption to cell division in the hair matrix makes the hair narrowed at its base and susceptible to breakage just above the zone of keratinization. The necrotic matrix forms plugs consisting of melanin, keratin, and inner root sheath which are extruded through the follicular opening. This process is known as tracheomalacia.

Sometimes, external factors like chemotherapy drugs, radiotherapy, oral contraceptives, vitamin A poisoning, chronic infections, other chemicals, etc. can result in an abnormal ending of the anagen phase.

According to Ayurveda, conditions like Indralupta (alopecia areata), Darunak (dandruff), Dadru Kushta (tinea infections), Eka kushta (psoriasis), etc. can also lead to anagen effluvium. This is due to high imbalances occurring in the dosha constituency of an individual.

Although severe hair loss is observed during anagen effluvium, hair starts to regrow again naturally after a few months in most cases.

The Catagen Phase – Transitional Phase

By the end of the anagen phase, the hair strand enters the catagen phase naturally. mitotic activity reduces and hair growth comes to a stop and hair gets detached from the root.

This is the transition or regression phase of hair growth which can be correlated to Pitta Kala in Ayurveda. During the catagen phase, The hair follicle renews itself by shrinking to 1/6th of its length.  Though the hair strand gets separated from the dermal papilla and stops receiving the nutrients, it does not shed off in the catagen phase as the shrunk walls of the hair follicle anchor the shaft part of the strand temporarily. And, this phase lasts for about 2-3 weeks in humans regardless of site.

At any given time, around 1% of your hair can be in the catagen stage on your scalp.

The Telogen Phase – Resting phase

By the end of the catagen phase, hair strand becomes a club and the dormant resting phase, telogen begins. Telogen hairs (also known as club hairs) have short, club-shaped roots that anchor them in the follicle. They lack a root sheath, unlike anagen hairs. The proximal part of the hair shaft is depigmented. Telogen hairs rest in the skin until they are forced out by new anagen hair growing underneath. At any given instance in time, approximately 10-15% of all hair follicles are in this phase.

This phase is closely related to Vata Kala in Ayurveda. Telogen phase lasts for 3-5 months during which before the follicle enters anagen again to emerge new hair emerge from the roots and slowly pushes up the previous club hair.

Telogen Effluvium: Telogen effluvium is the name for a common cause of hair prematurely excessive shedding of resting or telogen hair after some shock to the system. New hair continues to grow. This kind of hair loss is called Khalitya in Ayurveda.  As many as 70% of the anagen hairs can be precipitated into telogen, thus reversing the usual ratio.

This results in the hair prematurely entering the telogen phase, and eventually shed off.  Typical triggers include:

  • Childbirth: postpartum hair loss. This can resolve after a few months or transition into female pattern alopecia (round patches of hair loss or diffuse alopecia)
  • Physiological neonatal hair loss
  • Acute or chronic illness, especially if there is fever
  • Surgical operation
  • Accident
  • Psychological stress
  • Weight loss, unusual diet, or nutritional deficiency (eg, iron deficiency/)
  • Certain medications
  • Endocrine disorders (eg, hypothyroidism, hyperthyroidism)
  • Discontinuing the contraceptive pill
  • Overseas travel resulting in jetlag
  • Skin disease affecting the scalp (eg, erythroderma)
  • Excessive sun exposure.

 Telogen Effluvium mainly occurs due to an imbalance in Pitta and Vata doshas in an individual.

Exogen Phase

It is the last phase of the hair growth cycle when the hair strand completely detaches from the scalp and sheds off. This is the hair that you notice falling out while you comb or brush every day as around 50-100 strands undergo the exogen phase daily naturally.

Typically, hair growth lasts for about 4-7 years. However, it only happens for the first 2-3 cycles. As already discussed above, with growing age, the duration of the anagen phase shortens and the hair that grows back is thinner than previous hair. This can be related to the altering influence of different doshas as the individual grows.

At any point, you need to evaluate if you have normal hair fall caused by the natural hair growth cycle and understand your dosha imbalances to check if you are going through anagen effluvium or telogen effluvium.

Ayurveda bestows different dosha-specific herbal formulations which target the root cause of your hair loss while keeping your dosha levels in equilibrium.

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