Hair
compressed, keratinized cells that arise from hair follicles, the sacs that enclose the hair fibers
Hair is a filamentous biomaterial that grows on the skin of mammals, including humans. It is composed mainly of keratin, a protein that gives hair its strength and flexibility. Hair growth is regulated by a complex interplay of hormones, genetics, and environmental factors.
The structure of hair consists of three layers: the cuticle, cortex, and medulla. The cuticle is the outermost layer that protects the hair from damage and gives it shine. The cortex is the thickest layer and contains the pigment that gives hair its color. The medulla is the innermost layer and is present only in some types of hair.
The growth cycle of hair involves three phases: anagen, catagen, and telogen. During the anagen phase, the hair grows actively from the hair follicle. The catagen phase is a transitional phase when hair growth slows down and the hair follicle shrinks. The telogen phase is a resting phase during which the hair follicle remains inactive before the hair falls out.
Hair serves several important functions, including protection from the sun and physical damage, insulation from the cold, and sensory perception. Hair can also be used as a means of social communication and identity.
However, excessive hair growth or loss can be a sign of underlying health issues or hormonal imbalances. It is important to seek medical advice if you experience sudden or significant hair loss or growth.
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