The document summarizes the structure and functions of skin, hair, and nails. It describes the three layers of skin - the epidermis, dermis, and subcutaneous layer. The epidermis is protective and stratified, while the dermis provides support. Hair comes in two types - vellus and terminal hair. Glands in the skin include sebaceous and sweat glands. Nails are made of keratin and can provide signs or clues. The main functions of skin are protection, perception, temperature regulation, identification, communication, wound repair, absorption, and excretion.