STUDY GUIDE-THE TISSUE LEVEL
I. INTRODUCTION
A. A tissue is a group of similar cells that usually have a similar embryological origin and are
specialized for a particular function.
1. The nature of the extracellular material that surrounds the connections between the
cells that compose the tissue influence the structure and properties of a specific tissue.
2. The science that deals with the study of tissues is called histology.
B. Pathologists, physicians who specialize in laboratory studies of cells and tissues, aid other
physicians in making diagnoses; they also perform autopsies. Analysis of biopsies, samples
of living tissue removed for microscopic examination, is a chief responsibility of a
pathologist.
II. TYPES OF TISSUES AND THEIR ORIGINS
A. Depending on their function and structure, the various tissues of the body are classified into
four principal types.
1. Epithelial tissue covers body surfaces, lines hollow organs, body cavities, and ducts;
and forms glands.
2. Connective tissue protects and supports the body and its organs, binds organs together,
stores energy reserved as fat, and provides immunity.
3. Muscle tissue is responsible for movement and generation of force.
4. Nervous tissue initiates and transmits action potentials (nerve impulses) that help
coordinate body activities.
5. Clinical connection: biopsy
III. CELL JUNCTIONS
A. Cell junctions are points of contact between adjacent plasma membranes.
B. Depending on their structure, cell junctions may serve one of three functions.
1. Some cell junctions form fluid-tight seals between cells.
2. Other cell junctions anchor cells together or to extracellular material.
3. Still others act as channels, which allow ions and molecules to pass from cell to cell
within a tissue.
C. The five most important kinds of cell junctions are tight junctions, adherens junctions,
desmosomes, hemidesmosomes, and gap junctions.
