Eyelashes are small, curved hairs that grow along the edges of the upper and lower eyelids. This article explores the materials that comprise eyelashes, their structural organization and growth patterns, and their biological roles.
The Core Components of Eyelashes
Eyelashes are primarily composed of a resilient protein called keratin. This fibrous protein is the same substance that forms human hair and fingernails. Keratin provides eyelashes with their toughness and flexibility. Approximately 90% of an eyelash’s composition is keratin.
Beyond keratin, eyelashes contain melanin, a pigment that gives them their distinct color. The amount of melanin present dictates the shade, with higher concentrations resulting in darker lashes. The remaining 10% consists of water and lipids, which contribute to their overall structure.
Eyelash Structure and Growth Cycle
An eyelash originates from a hair follicle embedded within the eyelid skin. Each lash consists of a visible hair shaft, a root beneath the skin, and a bulb at its base where new growth begins. The bulb connects to the dermal papilla, which provides the necessary blood supply and nourishment for the lash to grow. Eyelash follicles are shorter than those found on the scalp, influencing their maximum length.
Eyelashes undergo a continuous cycle of growth, transition, and rest, which typically spans four to eleven months. The first stage is the anagen, or growth phase, where the lash actively lengthens. This phase usually lasts between 30 to 45 days, with lashes growing approximately 0.12 to 0.14 millimeters per day. At any given time, 35-40% of upper eyelashes are in this active growth stage.
Following the anagen phase is the catagen, or transition phase, lasting about two to three weeks. During this period, the eyelash stops growing, and its follicle begins to shrink and detach from its blood supply. The final stage is the telogen, or resting phase, which can last for three to four months. In this phase, the mature lash rests before a new lash begins to form underneath it, eventually causing the old one to shed naturally.
The Essential Functions of Eyelashes
Eyelashes serve as a protective barrier for the eyes. They effectively catch airborne particles like dust, debris, and pollen before these irritants can reach the sensitive eye surface. When the eyelids are closed, eyelashes form a comprehensive shield against foreign matter. They also regulate the amount of light, wind, and moisture that contacts the eye, helping to maintain a stable tear film and prevent dryness.
Beyond their physical shielding capabilities, eyelashes possess a sensory function. They are highly sensitive to touch, similar to whiskers. If something, even a slight air movement, brushes against an eyelash, it triggers an involuntary blink reflex. This rapid protective response helps to safeguard the eye.