where are hair follicles located in the skin
Hair follicle The hair follicle is a dynamic organ found in mammalian skin.[1] 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.[1] 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.[1] 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.[1]
Human skin Epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called stratum corneum and are sloughed off, or desquamated. This process is called keratinization and takes place within weeks. The outermost layer of the epidermis consists of 25 to 30 layers of dead cells.
Small intestine Absorption of the majority of nutrients takes place in the jejunum, with the following notable exceptions:
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