Morphogenesis of Yak Embryonic Skin and Its Appendages

Through embryonic tissue microarray and HE staining,this study found that the initial differentiation of embryonic skin has been starting at 35th day of embryonic stage,then epidermis experienced stratification and dermis experienced extracellular matrix fibers accumulation,formed a typical structure of mammalian skin.Hair follicle morphogenesis begins at 75th day of embryonic stage and then undergo several key stages of hair placodes,hair buds,hair nails and hair follicle differentiation and maturation.The primary hair follicle formation was accompanied by several waves of secondary hair follicle morphogenesis.Finally coat system consists of three types of hair follicles with scattered distribution.The morphogenesis of sebaceous glands and sweat glands associated with hair follicle development.Through the process of morphogenesis and differentiation,a hair follicle-sebaceous gland-sweat gland unit was formed.This characteristic reflects its environmental adaptability.