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The “hair shaft” refers to the visible part of the hair that protrudes from the skin. It consists of dead tissue produced by the living cells of the hair follicles in the dermis (the second layer of the skin). The hair shaft itself consists of three main layers:
Cuticle is the outermost layer of the hair shaft, which consists of overlapping scales that protect the hair and give it shine. The cuticle protects the inner area of the hair from external damage caused by environmental influences and mechanical stress such as brushing and styling.
Cortex (hair cortex) is the middle and thickest layer of the hair shaft, which consists of long fibers of keratin and is responsible for the strength, elasticity and color of the hair. The physical and chemical properties of the cortex largely determine the texture and quality of the hair.
Medulla is the innermost layer found in some hair types and is not always continuous. The medulla consists of a series of loosely packed cells and air pockets and plays a less important role in the physical strength of the hair.
Together, these layers form the hair shaft, which is continuously pushed out of the scalp as the hair grows. The structure and health of the hair shaft are crucial for the appearance and texture of the hair. Damage to the hair shaft, such as split ends or breakage, affects the external appearance of the hair and can be caused by various factors such as chemical treatments, heat styling and mechanical stress.
