In order to provide young people with a didactic way of starting the subject of Structural Pathology, this summary has been prepared to guide undergraduate students, which will help them to later, on an individual level, delve deeper into the intricacies of medicine. The subject has been reviewed in the relevant chapters, starting with the basic topics, and then continuing with specific diseases. On some occasions, in the chapter on neoplasias reference is made to molecular matters essential for understanding the processes. It begins with adaptation processes in which physiological mechanisms are brought into play in order for the cell to maintain its viability. The mechanisms that damage its integrity and that ultimately lead to cell death are indicated. Subsequently, general topics of pathology are analyzed, trying to explain its mechanisms to understand them in their entirety, and finally, specific diseases are addressed in the same way.