Human Structure Virtual Histology
    Epithelia Structure, Function and Gland Classification

    Epithelium, one of the four basic tissue types of the body, is characterized by:
    • An apical or free surface
    • A basal lamina (basement membrane), which anchors the basal surface to underlying structures
    • Polarity due to distinct lipid and protein components at each surface and localization of organelles within the cytoplasm
    • Close apposition and adhesion to neighboring epithelial cells

    In general, epithelia function to:

    • Line and protect the surfaces of the body and organ cavities (e.g. oral mucosa and lining epithelium of the esophagus)
    • Allow for absorption (e.g. nutrients and water in the gastrointestinal tract)
    • Produce secretions (e.g. mucous, digestive enzymes, and hormones)

    The classification of an epithelial layer is based on three features:

    1. The shape of cells that comprise its free surface (squamous, cuboidal, or columnar)
    2. The number of cellular layers (one layer = simple, more than one layer = stratified)
    3. Specializations present at the apical or free surface (keratinization, cilia, microvilli, or stereocilia)

    The learning objectives for this module are:

    1. Classify epithelia by their major structural types and recognize these using light microscopy.
    2. Recognize by light microscopy the basic morphological features and staining differences within the secretory elements of serous and mucous exocrine glands.

    Let's start with simple squamous epithelium


     Lab Table of Contents | Glossary