The Science of Hair: Hair Structure and the Growth Cycle

When properly applied and maintained, hair extensions can blend seamlessly with your natural hair, giving you the desired look without damaging it.

Our hair is more than just for looks—it's a biological miracle that serves multiple purposes, from protection to temperature regulation. This article will help you understand hair structure and the growth cycle, helping you better care for your hair and address common concerns.

 

Hair anatomy 101

Before we discuss the intricacies of hair growth, it's essential to understand the basic anatomy of hair.

Types of hair

Human hair comes in two main varieties:

1. Vellus hair: This is the fine, short "peach fuzz" covering most of our body. It's usually colorless and barely noticeable.

2. Terminal hair: Thicker and longer, terminal hair is typically considered "hair." It includes the hair on our scalp, eyebrows, eyelashes, and body hair that develops during puberty.

Hair structure

Image: International Journal of Molecular Sciences

Each hair is composed of three main parts:

1. Hair shaft: The visible part of the hair that extends beyond the skin surface

2. Hair root: The portion of the hair below the skin's surface

3. Hair follicle: A sheath of skin and connective tissue that surrounds the hair root

Let's take a closer look at the components of a hair follicle:

 

The hair growth cycle

Image: International Journal of Molecular Sciences

The hair growth cycle consists of four distinct stages:

1. Anagen phase (Growth phase)

   1. Duration: 2-7 years for scalp hair

   2. Characteristics:

      1. Active cell division in the hair matrix

      2. Continuous hair growth at about 1 cm per month

      3. About 80-90% of scalp hairs are in this phase at any given time

2. Catagen phase (Transitional phase)

   1. Duration: 2-3 weeks

   2. Characteristics:

      1. Hair growth stops

      2. Hair follicle shrinks and detaches from the dermal papilla

      3. Only about 1% of hairs are in this phase at any time

3. Telogen phase (Resting phase)

   1. Duration: 3-4 months

   2. Characteristics:

      1. Hair is no longer growing but remains attached to the follicle

      2. About 10-15% of hairs are in this phase

      3. New hair begins to form in the follicle beneath the resting hair

4. Exogen phase (Shedding phase)

5. Characteristics:

   1. Old hair is shed from the follicle

   2. Typically, 50-100 hairs are shed per day

   3. New hair continues to grow in the follicle

Understanding these stages is crucial for addressing hair concerns and promoting healthy growth.

Factors influencing hair growth and health

Several factors can affect the hair growth cycle and overall hair health:

1. Genetics: Determines hair color, texture, and susceptibility to certain hair conditions

2. Nutrition: Proper intake of proteins, vitamins, and minerals is essential for healthy hair

3. Hormones: Hormonal changes can significantly impact hair growth and loss

4. Environmental factors: Exposure to UV radiation, pollution, and harsh chemicals can damage hair

Common hair growth concerns

Hair loss (Alopecia)

There are several types of alopecia, including:

1. Androgenetic alopecia: Male and female pattern baldness

2. Alopecia areata: An autoimmune disease causing patchy hair loss

3. Telogen effluvium: Temporary hair shedding due to stress or other factors

Causes of hair loss can include:

• Genetics

• Hormonal changes

• Medical conditions

• Medications

• Stress

• Nutritional deficiencies

Treatment options for hair loss may include:

• Topical medications (e.g., minoxidil)

• Oral medications (e.g., finasteride)

• Hair transplantation

• Scalp micro-pigmentation

• Low-level laser therapy

Slow hair growth

Some people may experience slower-than-average hair growth. This can be due to:

• Genetics

• Age

• Nutritional deficiencies

• Damage to the hair follicles

To promote faster hair growth, maintain a healthy diet rich in proteins, vitamins, and minerals and massage the scalp to stimulate blood flow. Also, avoid harsh chemical treatments and heat styling and use gentle hair care products.

Thinning hair

Thinning hair can occur due to:

• Age-related changes in hair follicles

• Hormonal imbalances

• Nutritional deficiencies

• Certain medical conditions

To address thinning hair, use volumizing hair products, consider hair thickening treatments, and consult a healthcare provider to rule out underlying medical conditions.

Nurturing healthy hair growth

To promote optimal hair health and growth:

1. Diet and supplements:

   1. Consume a balanced diet rich in protein, iron, vitamins A, C, D, and E, and fatty acids
   2. Consider supplements like biotin, collagen, omega-3 fatty acids, and amino acids to augment the hair cycle

2. Scalp care:

   1. Keep the scalp clean and free from buildup

   2. Use a gentle shampoo and conditioner suitable for your hair type

   3. Massage the scalp regularly to stimulate blood supply and flow

3. Hair care practices:

   1. Avoid excessive heat styling and chemical treatments

   2. Use a wide-toothed comb to detangle wet hair gently

   3. Trim hair regularly to prevent split ends

How hair extensions work with natural hair

Hair extensions can be a great way to add length, volume, or both to your natural hair. They work by attaching additional hair, either synthetic or human, to your existing hair. Here's how different types of extensions interact with your natural hair:

1. Clip-in extensions: Temporary and easy to apply, these attach to your natural hair with small clips

2. Tape-in extensions: Thin wefts of hair are sandwiched between sections of your natural hair using adhesive tape

3. Sew-in extensions: Wefts of hair are sewn onto small braids of your natural hair

4. Fusion extensions: Small sections of extension hair are bonded to your natural hair using heat or adhesive

When properly applied and maintained, hair extensions can blend seamlessly with your natural hair, giving you the desired look without damaging it.

The science is everything

Understanding the science behind hair structure and growth is key to maintaining healthy, beautiful hair. By knowing the hair growth cycle and the factors that influence it, you can effectively make informed decisions about your hair care routine and address common concerns.

Remember that everyone's hair is unique, and what works for one person may not work for another. If you're experiencing persistent hair issues, it's always best to consult with a healthcare provider or trichologist for personalized advice and treatment.

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Frequently asked questions

What structure is responsible for hair growth?

The hair bulb, located at the bottom of the hair follicle, is responsible for hair growth. It contains the hair matrix cells and the dermal papilla, which work together to produce new hair cells and nourish the growing hair.

Does hair grow from root to tip?

Yes, hair grows from root to tip. New cells are produced in the hair matrix at the base of the hair follicle. As these cells divide and push upward, they harden and form the hair shaft, which emerges from the skin's surface.

What are the four stages of hair growth?

The four stages of hair growth are:

1. Anagen phase (Growth phase): Active hair growth lasting 2-7 years for scalp hair.

2. Catagen phase (Transitional phase): A brief 2-3 week period where growth stops and the follicle shrinks.

3. Telogen phase (Resting phase): A 3-4 month period where the hair remains in the follicle but doesn't grow.

4. Exogen phase (Shedding phase): The old hair is shed, allowing new growth.

Understanding these stages of hair growth can help you better care for your hair and address any growth-related concerns.