Hair follicle

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The hair follicle is an organ found in mammalian skin. Residing in the dermal layer of the skin, each hair follicle is made up of 20 different types of mammalian cells, each with distinct functions. Hair follicles undergo a process of cellular differentiation. The hair follicle regulates hair growth via a complex interaction between hormones, neuropeptides, and immune cells. This complex interaction induces the hair follicle to produce different types of hair as seen on different parts of the body. For example, terminal hairs grow on the scalp, and lanugo hairs are seen covering the bodies of fetuses in the uterus, some newborn babies, and oftentimes the bodies of humans with very low bodyweight, such as anorexics. The process of hair growth occurs in distinct sequential stages: anagen is the active growth phase, catagen is the regression phase of the hair follicle, telogen is the resting stage, exogen is the active shedding of hair phase and kenogen is the phase between the empty hair...

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