Topic overview

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Hair grows from follicles that extend into the dermis or hypodermis. The follicle’s bulb contains the growth matrix and a dermal papilla, while the shaft has medulla, cortex, and cuticle layers. Hair pigmentation depends on melanin transfer in the bulb, and its growth proceeds through anagen, catagen, and telogen phases. Nails are hard-keratin plates produced by the germinative matrix beneath the proximal nail fold. The glands in this topic have contrasting roles: eccrine glands support thermoregulation, apocrine secretions can develop odor through bacterial breakdown, and sebaceous glands release their product by holocrine secretion. Understanding their locations, structures, and secretion patterns provides a foundation for relating integumentary anatomy to function.