Embryology of the pilosebaceous unit

Abstract

In mammals, hairs fulfil a number of important functions including thermoregulation, collecting sensory information, protection against environmental stressors, social communication and mimicry [1]. Hairs are produced by the pilosebaceous unit that consists of the hair follicle and associated structures such as sebaceous gland, perifollicular nerve fibres and arrector pili muscle [1, 2]. In humans, hair follicles are distributed throughout the body with exception of the soles, palm and part of the external genitalia and produce two major hair types (terminal and vellus hairs) that show distinct morphology and distribution patterns [3].