This lecture covers the four classes of tissues: epithelial, connective, muscular, and nervous tissues, focusing on their definitions, characteristics, and functions. It explains the structure of epithelial cells, the composition of connective tissue, and the types of muscle tissues. The lecture also discusses the role of epithelia in covering body cavities and forming glandular elements, as well as the interaction between epithelial and connective tissues in the human body, illustrated with examples like the skin and mucosa.