<Tr> <Th> FMA </Th> <Td> 70660 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The hair follicle is a dynamic organ found in mammalian skin . It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions . 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 utero and in some new born babies . The process of hair growth occurs in distinct sequential stages . The first stage is called anagen and is the active growth phase, catagen is the resting stage, telogen is the regression of the hair follicle phase, exogen is the active shedding of hair phase and lastly kenogen is the phase between the empty hair follicle and the growth of new hair . </P> <P> The function of hair in humans has long been a subject of interest and continues to be an important topic in society, developmental biology and medicine . Of all mammals, humans have the longest growth phase of scalp hair compared to hair growth on other parts of the body . For centuries, humans have ascribed esthetics to scalp hair styling and dressing and it is often used to communicate social or cultural norms in societies . In addition to its role in defining human appearance, scalp hair also provides protection from UV sun rays and is an insulator against extremes of hot and cold temperatures . Differences in the shape of the scalp hair follicle determine the observed ethnic differences in scalp hair appearance, length and texture . </P>

What is the function of a hair follicle