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Chapter 4 (Epithelial Tissue)

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  • Unicellular organisms

    One celled organisms; independent creatures

  • Tissue

    Group of cells that are similar in structure and perform a common or related function

  • Histology

    Study of tissues

  • Microscopy

    Allows us to study tissue structure

  • Microscopy Requirements

    1. specimen must be fixed (preserved)

    2. specimen must be cut into sections (slices)

    3. specimen must be stained (enhanced)

  • Epithelial Tissue

    sheet of cells that covers a body surface or lines a body cavity

  • Covering and lining epithelium

    forms outer layer of skin & covers walls of organs in ventral cavity & lines open cavities

  • Glandular Epithelium

    forms the glands of the body

  • Characteristics of Epithelium

    1. Polarity

    2. Specialized Contacts

    3. Supported by Connective Tissue

    4. Avascular but Innervated

    5. Regeneration

  • Epithelium Polarity

    have 2 surfaces that differ in structure and function (apical & basal)

  • Specialized Contacts

    epithelial cells fit closely together to form continuous sheets; except for glandular

    • connected by tight junctions and desmosomes

  • Supported by Connective Tissue

    all Epithelial sheets rest on Connective tissue

  • Avascular but Innervated

    all epithelial tissue is avascular & innervated

  • Regeneration

    has high regeneration capacity as long as it has adequate nutrition

  • Apical Surface

    not attached to surrounding tissue & is exposed to either the outside of the body/cavity

  • Basal Surface

    attached to the underlying connective tissue

  • Microvilli

    finger-like extensions that increase surface area in epithelial that absorbs

  • Basal Lamina

    adjacent to basal surface; noncellular adhesive supporting sheet

  • Basement Membrane

    consists of 2 layers (basal lamina & reticular lamina); reinforces & defines epithelial boundary

  • Reticular Lamina

    Layer of ECM

  • Innervated

    supplied by nerve fibers

  • How are epithelial cells nourished?

    substances diffuse from blood vessels in underlying connective tissue

  • Classifications of Epithelial Tissue

    Simple, Stratified, Pseudo Stratified

    Squamous, Cuboidal, Columnar

  • Endothelium

    provides a slick, friction-reducing lining in lymphatic vessels

  • Mesothelium

    Epithelium found in serous membranes

  • Stratified cuboidal

    Rare in the body; found in sudoriferous glands

  • Stratified columnar

    Found in the pharynx

  • Gland

    cells that make and secrete a particular product

  • Gland Classifications

    endo/exo-crine & uni/multi cellular

  • endocrine glands

    produce and secrete hormones directly into extracellular space via exocytosis

  • Exocrine glands

    secrete products onto body surface or into body cavities via exocytosis

  • Unicellular exocrine glands

    mucous & goblet cells

  • Goblet cells

    produce mucin; sprinkled in respiratory tracts

  • Multicellular exocrine glands

    have 2 basic parts: duct & secretory unit; supportive connective tissue surrounds & supplies secretory unit

  • Multicellular Exocrine Glands Classifications

    simple/unbranched or compound/branched ; tubular/alveolar/tubualveolar

  • Modes of secretion

    1. Merocrine Glands

    2. Holocrine Glands

    3. Apocrine Glands

  • Merocrine Glands

    secrete using exocytosis; no alterations occur to the cell

  • Holocrine Glands

    glands accumulate products until they rupture

  • Apocrine Glands

    accumulate product until part of cell falls off; regenerates later