Many individuals often wonder if hair grows from its roots or its ends. This common question highlights a misunderstanding of hair’s biological structure. Understanding hair’s biology is key to answering this question. This article explores the science behind hair growth, explaining where and how hair originates.
The Hair Follicle and Its Role
Hair growth originates exclusively from the hair follicle, a specialized, tube-like structure embedded within the skin. At the base of each follicle lies the hair bulb, which houses two components: the dermal papilla and the germinal matrix. The dermal papilla is a small, cone-shaped structure rich in blood vessels that provide nutrients and oxygen to the rapidly dividing cells. Surrounding the papilla is the germinal matrix, an area of active cells where new hair cells are continuously produced.
These newly formed cells in the germinal matrix undergo keratinization, filling with a protective protein called keratin and hardening. As more new cells are generated, they push the older, keratinized cells upwards. This continuous upward movement forms the hair shaft, the visible part of the hair that extends from the scalp.
The Hair Growth Cycle
Hair growth is not a continuous, uninterrupted process but rather occurs in a cyclical pattern involving three main phases. These phases include Anagen, Catagen, and Telogen, ensuring that hair is constantly renewed. The Anagen phase is the active growth period, during which cells in the hair follicle rapidly divide, causing the hair to lengthen. For scalp hair, this phase typically lasts between two and eight years, with hair growing approximately one centimeter per month.
Following the Anagen phase is the Catagen phase, a short transitional stage that signals the end of active growth. During this period, which lasts about two to three weeks, the hair follicle shrinks and detaches from its blood supply. The final stage is the Telogen phase, a resting and shedding period that typically lasts for two to four months. During Telogen, the old hair is shed from the follicle, making way for a new hair to begin its Anagen phase. Each hair follicle operates independently, meaning different hairs are in different phases of the cycle at any given time, preventing all hair from shedding simultaneously.
Why Ends Don’t Grow
Once a hair strand emerges from the scalp, it is no longer living tissue. The visible hair shaft is composed primarily of dead, hardened protein called keratin. Unlike the hair follicle embedded in the skin, the hair shaft itself contains no living cells, nerves, or blood vessels. This means the ends of the hair, or any part of the hair shaft outside the scalp, cannot grow, heal, or repair themselves.
Because the visible hair is non-living, cutting the ends does not stimulate growth from the root, nor can it make hair grow faster. Split ends, a result of damage to the hair shaft, cannot “heal” or fuse back together. Any perceived improvement after a trim comes from removing the damaged, frayed ends, making the hair appear healthier and fuller. All true hair growth originates from the active, living cells within the hair follicle beneath the skin’s surface.