Introduction
While the cell is considered a basic unit of life, complex functions in multicellular animals require interaction and cooperation between cells. With increased development, specialized functions appear in subpopulations of cells.
Many of these activities are attributed to types of tissues. For example, nervous or neural tissue composed of neurons and supporting neuroglial cells allows generation, transmission, and interpretation of electrical signals. This is the hallmark of the nervous system. Another tissue type, epithelium, is widely dispersed in animals and generally is involved in covering surfaces, that is, skin or peritoneum, in the development and function of various glands, that is,mammary, pituitary, pancreas, and so forth. Muscle tissue is readily recognizable because of its capacity to generate motion and distinct appearance. It is worth remembering, however, that there are three classes of muscle tissue: skeletal or voluntary, cardiac, and smooth muscle. The final tissue type, connective tissue, is also very widely distributed and is usually found as a component of the other tissue types. This means that when you study preparations of various tissues, although there will be emphasis on particular cells (epithelial, muscle, or neural), various connective tissue elements are also present. Lastly, there are also subclasses of connective tissues, that is, bone, cartilage, and blood. Our purpose in this chapter is to aid your activities in the laboratory, especially time
spent looking at samples in the microscope, to reinforce your other reading and attendance of lectures, and to give you some rudimentary understanding of histology.