The lesson discusses the function and structure of the skin, emphasizing its role as the body’s largest organ, which accounts for 16% of body weight and covers approximately 1.7 square meters. The skin protects, senses the environment, and regulates body temperature using its three layers: the epidermis, dermis, and hypodermis. It also serves as a defense barrier, with components like keratinocytes, Merkel cells, and Langerhans cells working alongside thousands of microbial species to maintain immune vigilance and physiological balance.