As the structural and functional relationships of various cells, tissues, and organs are considered throughout the course, always be aware of one simple concept - all of the tissues and organs of the body are composed of cells and the extracellular products of cells (the matrix). It is for this reason that we emphasize the basic components of cells and their matrices during the early portion of the course. With an understanding of the nature of the relationship between cells and their matrices, we can proceed to the study of the organization of these two components into the basic tissues of the body.
There are only four basic tissues in the body, although each category can be subdivided. In turn, the four basic tissues are organized into the various organs of the body, and these generally exist as interrelated functional units termed organ systems.
