Hair is a component of the integumentary system and extends downward into the dermal layer, where it sits in the hair follicle. Humans have approximately five million hair follicles, which offer protection from cold and UV radiation, produce sebum, and can have a significant psychological impact when growth or structure is unbalanced.
At a microscopic level, each hair's variety in length, color, diameter, and cross-sectional shape creates the characteristic profiles seen across ethnic groups and among individuals. This activity will discuss the physiology of hair, cellular components, mechanisms of growth and differentiation, and its clinical significance.
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