Hair anatomy is a complex system of structures. Human hair comprises a protein called keratin, which contains many cysteine amino acids. Keratin is also found in nails and skin, although not as much as in hair.
The outermost layer of your hair is made up of dead cells called keratinocytes that form a protective protein layer around your strands. Keratinocytes grow deep into your follicle, converting them into hard keratin by enzymes called proteases that break down proteins into smaller pieces. Keratin becomes part of your strands' outermost layer, forming scales overlapping as roof tiles do. These scales give each strand its characteristic texture and shape — think about how soft strands feel compared to curly ones or how straight strands look compared to kinky ones.
Anatomy of Hair includes
What is a Hair Follicle?
Hair follicles are small, tubular structures that produce and protect hair. They are located in the dermis portion of the skin, each associated with a sebaceous gland. Hair is produced in a cycle, with two active phases (anagen and catagen) and one resting phase (telogen). The first phases together make up about 99% of the hair growth cycle.
The hair follicle is composed of three main structures:
The root sheath: A thin layer of epidermis continuous with the basement membrane surrounding the hair shaft's root, except where it bulges into a papilla to form an arrector pili muscle attachment, which contracts when we get goosebumps.
The dermal papilla: A connective tissue structure inside the dermis that produces new cells to form the outer layer of a growing hair shaft and nourishes them as they grow out into an expanded outer layer made up of keratinized cells that are created by keratohyalin granules within it.
The bulge area: Located at the base of each follicle's papilla, where it connects with muscle fibers via an arrector pili muscle attachment.
There are three layers to the human hair follicle.
The outer layer is called the cuticle and is made of overlapping scales. The middle part is the cortex and consists of densely packed cells. Underneath this is the medulla, which is hollow and filled with air-filled spaces.
The Cuticle Layer
The cuticle layer covers all but the tips of the shaft and is formed by overlapping. These scales are made up of keratin protein, which includes a protective coating over each strand of hair. This coating can be damaged by chemical treatments or heat-styling tools like blow dryers or flat irons (which create more friction between each strand). Damage to this layer results in frizz in people who have naturally straight hair since it interferes with moisture retention at the base of each strand. It contains keratin, a protein that makes up 90% of your hair's structure and strength. The medulla anchors the cortex, a tube-like form of living cells called melanocytes.
The Cortex Layer
The cortex layer makes up most of each strand's mass and contains keratinized cells — cells filled with keratin protein — that give each strand.
It acts as a shock absorber for impact forces on the hair shaft. This layer is found only in the center of each strand and consists of long, thin cells called melanocytes (naturally occurring pigments).
Learning your hair parts and their functions helps you understand hair growth's phases. It also gives you a foundation for treatments, especially when your hair is not shedding. Invest 1-2 hours in Hair Loss courses and check what the experts say.