Where Cutaneous Conditions Occur
The skin weighs an average of 4 kilograms (8.8 lb), covers an area of 2 square metres (22 sq ft), and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. There are two main types of human skin: glabrous skin, the nonhairy skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin. Within the latter type, there are hairs in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle. In the embryo, the epidermis, hair, and glands are from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.
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