7-2.Structure of skin
	It is necessary to know the generation stage of the skin when thinking about the aging of the skin.
	Cause of causing aging of skin. ●The fertilized egg brought up by the mother's body becomes gastula repeating the cell division. Gastrula is formed with ectoderm, mesoderm, and endoderm. The skin is made from ectoderm and mesoderm. It changes into two layers when the cell in one layer queues up first, and the viviparity two months are passed by a thin film. As the formation, because it is still imperfect, the cell of dermis is few, and mamillary body is not formed, it is a straight line simple skin. After it is born, various stimulation is received as it differs from the interior of the womb environment, and it touches air. Therefore, the blood circulation becomes active, it sees in externals, and it is seen the pink color. Recently, because the epidermal is still thin, and the coloring matter granulated powder is also a little, the blood circulation that the transparency of the skin is high, and active is reflected in the skin colour and it is seen the pink color.
	In the viviparity about 3 months Collagen Sen is generated. 6 months from viviparity 4 months Epidermis keratinization can happen, it have the skin attachment organs such as the hair gland, sweat glands, and hairs, and rough of the skin is in order. 8 months from viviparity 7 months Erastin Sen is generated, mamillary develops, and the boundary side of the corium and the epidermal becomes a shape of waves, and it seems to be a skin on the function side and it becomes it. Infancy infant period It is still thin with the epidermal and the corium. However, the hypodermis-subcutaneous tissue is thick. (soft fair velvety skin feeling) Infant period The coloring matter granulated powder increases, too and it becomes adult's color. Collagen fiber increases in the corium, too and strength is equipped. Adolescence Skin completion After completing secondary sex characteristics The woman becomes a strong, stout straight line man's skin, and becomes flexible and a curve. Moreover, it is time when acne can be done easily though the secretion of sebum gland becomes active, too and enriching increases to the skin. 24 years old from 20 Peak time to which all of amount of fat of row of amount of moisture of epidermis and collagen of corium and hypodermis-subcutaneous tissues proper, elastic, fresh skin is kept. About 25 years old The aging of the skin starts when bodily functions enter the decline period. Female about 45 years old The perimenopausal symptom appears. (man about 55 years old)