The question of whether hair is alive or dead often arises when considering its unique properties. Hair appears to grow, yet it lacks sensation and does not heal. Understanding the biological structures and processes involved in hair formation clarifies this common query, revealing that different parts of hair possess distinct biological characteristics.
Hair’s Basic Components
Hair is composed of two primary parts: the hair follicle and the hair shaft. The hair follicle is a tunnel-like structure embedded within the skin, extending into the dermis. It serves as the growth center for hair. At the base of the hair follicle lies the hair bulb, which houses the dermal papilla and hair matrix cells. The dermal papilla, rich in blood vessels, provides essential nutrients and oxygen to the hair for its growth.
The hair shaft is the visible portion of the hair that extends above the skin’s surface. It is the part of the hair that is typically styled or cut.
How Hair Develops
Hair growth originates within the hair bulb, where specialized cells called keratinocytes in the hair matrix rapidly divide. As new cells are produced, older cells are pushed upward through the hair follicle.
During this ascent, these cells undergo a process called keratinization. In keratinization, cells fill with a tough protein called keratin and lose their internal structures, including their nuclei and organelles, effectively becoming non-living. This transformation results in hardened, compact cells that form the hair shaft. The continuous division of cells in the hair matrix and subsequent keratinization push the developing hair strand outward from the skin.
Living Roots, Lifeless Strands
The visible hair shaft is composed of dead, keratinized cells. These cells are densely packed with keratin protein, which provides hair with its strength and structure.
Because the hair shaft lacks living cells, nerves, and blood vessels, cutting hair does not cause pain. The sensation felt when hair is pulled originates from the living hair follicle, which is rich in nerve endings beneath the skin’s surface.
Unlike living tissues, the hair shaft cannot heal itself from damage, such as split ends, because it is no longer biologically active and cannot repair its cellular structure. The only living component of hair is the follicle, which sustains hair growth and determines its characteristics.