Hair Anatomy and Physiology
Demystifying the structure and growth of hair.
1.1 Hair Anatomy and Composition: Demystifying the Shaft
Hair is a complex structure primarily composed of proteins, water, and micronutrients. Its natural moisture is maintained by sebum, an oil produced by the sebaceous glands at the hair follicle. The visible part of the hair, the shaft, is a three-layered structure.
The Medulla
The **medulla** is the soft, hollow center of the hair shaft. Think of it like the "pith" inside a plant stem. It's only found in thicker hair types, not in fine hair. Its presence can make hair more likely to split.
The Cortex
The **cortex** is the main body of the hair. It makes up most of the hair's mass and strength, like the "trunk" of a tree. This is where the pigment that gives hair its color is stored.
The Cuticle
The **cuticle** is the outermost protective layer, made of tiny, overlapping cells that look like "shingles on a roof" or "fish scales." When hair is healthy, these scales lie flat, making the hair look shiny and feel smooth.
This cuticle layer is a great indicator of hair health. When hair is damaged by heat or harsh products, the cuticle cells lift and create gaps. This is why damaged hair looks frizzy and dull—it's losing moisture through these gaps, like a leaky roof. Many hair treatments are designed to flatten these scales again to restore shine and strength.
Cell Membrane Complex (CMC)
The **Cell Membrane Complex (CMC)** acts like a glue or "intercellular cement" that holds the hair cells together. When you bleach or straighten your hair, this "glue" can be broken down. This is why over-processed hair can feel fragile and brittle—the internal structure is literally falling apart.
1.2 Hair Physiology: The Growth Cycle and Its Implications
Hair growth is a cyclical, slow process that occurs in four distinct phases:
Anagen Phase
This is the **active growth phase**, which can last from 2 to 7 years. During this time, the hair is actively growing from the follicle. The longer this phase lasts, the longer your hair can grow.
Catagen Phase
A short **transitional phase** lasting a few weeks. The hair follicle shrinks and detaches from its blood supply, preparing to rest.
Telogen Phase
A **resting phase** that lasts for a few months. The hair is fully formed but is not actively growing. A new hair begins to form beneath it.
Exogen Phase
The **final stage** where the old hair sheds to make way for the new hair. This is why it's normal to lose around 50-100 hairs a day.
**Myth vs. Reality**: Hair treatments don't make hair grow faster. The speed of growth is determined by genetics. However, treatments that strengthen the hair shaft can prevent breakage, which allows your hair to reach its full potential length. So it might feel like your hair is growing faster, but it's really just getting stronger and not breaking as often!
Hair Anatomy and Physiology
Demystifying the structure and growth of hair.
1.1 Hair Anatomy and Composition: Demystifying the Shaft
Hair is a complex structure primarily composed of proteins, water, and micronutrients. Its natural moisture is maintained by sebum, an oil produced by the sebaceous glands at the hair follicle. The visible part of the hair, the shaft, is a three-layered structure.
The Medulla
The **medulla** is the soft, hollow center of the hair shaft. Think of it like the "pith" inside a plant stem. It's only found in thicker hair types, not in fine hair. Its presence can make hair more likely to split.
The Cortex
The **cortex** is the main body of the hair. It makes up most of the hair's mass and strength, like the "trunk" of a tree. This is where the pigment that gives hair its color is stored.
The Cuticle
The **cuticle** is the outermost protective layer, made of tiny, overlapping cells that look like "shingles on a roof" or "fish scales." When hair is healthy, these scales lie flat, making the hair look shiny and feel smooth.
This cuticle layer is a great indicator of hair health. When hair is damaged by heat or harsh products, the cuticle cells lift and create gaps. This is why damaged hair looks frizzy and dull—it's losing moisture through these gaps, like a leaky roof. Many hair treatments are designed to flatten these scales again to restore shine and strength.
Cell Membrane Complex (CMC)
The **Cell Membrane Complex (CMC)** acts like a glue or "intercellular cement" that holds the hair cells together. When you bleach or straighten your hair, this "glue" can be broken down. This is why over-processed hair can feel fragile and brittle—the internal structure is literally falling apart.
1.2 Hair Physiology: The Growth Cycle and Its Implications
Hair growth is a cyclical, slow process that occurs in four distinct phases:
Anagen Phase
This is the **active growth phase**, which can last from 2 to 7 years. During this time, the hair is actively growing from the follicle. The longer this phase lasts, the longer your hair can grow.
Catagen Phase
A short **transitional phase** lasting a few weeks. The hair follicle shrinks and detaches from its blood supply, preparing to rest.
Telogen Phase
A **resting phase** that lasts for a few months. The hair is fully formed but is not actively growing. A new hair begins to form beneath it.
Exogen Phase
The **final stage** where the old hair sheds to make way for the new hair. This is why it's normal to lose around 50-100 hairs a day.
**Myth vs. Reality**: Hair treatments don't make hair grow faster. The speed of growth is determined by genetics. However, treatments that strengthen the hair shaft can prevent breakage, which allows your hair to reach its full potential length. So it might feel like your hair is growing faster, but it's really just getting stronger and not breaking as often!