Introduction to Histology and Basic Histological Techniques

Although histology is the microscopic study of tissues of living organisms, be they animals or plants, this textbook discusses only mammalian—more specifically, human—tissues. However, the term has evolved to have a broader concept, named microscopic anatomy , because its subject matter encompasses not only the microscopic structure of tissues but also those of the cell, organs, and organ systems.

The body is composed of cells, extracellular matrix, and a fluid substance, the extracellular fluid (tissue fluid), which bathes these components. Extracellular fluid, which is derived from plasma of blood, carries nutrients, oxygen, and signaling molecules to cells of the body. Conversely, waste products, carbon dioxide, signaling molecules, and additional products released by cells of the body reach blood and lymph vessels by way of the extracellular fluid. Extracellular fluid and much of the extracellular matrix are not visible in routine histological preparations, yet their invisible presence must be appreciated by the student of histology.

Moreover, the subject of histology encompasses more than just the microscopic structure of the body; it is also concerned with the body’s function. In fact, histology has a direct relationship to other disciplines and is essential for their understanding. This textbook intertwines the disciplines of cell biology, biochemistry, physiology, embryology, gross anatomy, and, as appropriate, pathology. Students will recognize the importance of this subject as they refer to the text later in their careers. An excellent example of this relationship should be evident when the reader learns about the histology of the kidney and realizes that it is the intricate and almost sublime structure of that organ (down to the molecular level) that is responsible for the kidney’s ability to perform its function. Alterations of the kidney’s structure are responsible for a great number of life-threatening conditions. Another example is the microscopic—indeed, molecular—structure of muscle cells. The ability to contract is intimately dependent on the microscopic, submicroscopic, and molecular organization of the various components of the muscle cell.

The remainder of this chapter discusses the methods used by histologists to study the microscopic anatomy of the body.