1. Epithelium Overview
    • All epithelia are supported by a basement membrane of variable thickness. Basement membranes separate epithelia from underlying supporting tissues and are never penetrated by blood vessels. (this is regarding outer layers of
    • epithelium. There are also inner layers… endothelium, but called epi)
  2. Epithelium Characteristics
    • Form continuous cell sheets
    • Thickness: one or more cell layers
    • Connected by adhesion plaques/cell junctions
    • Attached to basement membrane
    • Avascular: never penetrated by blood vessels
  3. Membrane Junction
    Zonula Occludens
    Tight junction -impermeable junction encircles cell
  4. Membrane Junction
    Zonula Aderens
    • Adhering junctions continuous intermediate junction
    • Cadherin
    • Actin filaments
  5. Membrane Junction
    Mascula Adherens
    • Desmosome - scattered spot-adhering junctions
    • Cadherin
    • Intermediate filament
  6. Membrane Junction
    Gap Junction
    • Communicating Nexus
    • -small chemicals pass through pores
  7. Hemidesmosome
    • Epithelial cells are linked to the subcellular matrix by a supportive basement membrane which also acts as a barrier. Anchorage of epithelial cells is through hemidesmosomes.
    • strong linkage between epi and basement membrane
  8. junctional epidermolysis bullosa
    Genetic or acquired defect in HD (hemidesmosome)
  9. Oral EB-mucous membrane pemphigoid
    • • An oral autoimmune disease
    • • Auto-antibodies against the basement membrane antigens
    • • Results in epithelial separation from connective tissue and ulceration.
    • Mucous membrane pemphigoid showing ulceration of the maxillary gingiva, erosions
    • Lack of brushing-> pitted enamel and tooth carie
  10. Microvilli
    • • Extension of cytoplasmic processes
    • • Increase surface area for resorption
    • • Prominent in small intestine and proximal renal tubules
    • • Appear as “brush borders” in H & E sections
  11. Cilia
    • Pseudostratified ciliated epithelium
    • Ciliary action serves to propel mucous and trapped debris out of the respiratory tract.
  12. Classification of Epithelium
    • • Number of layers - Simple vs. stratified
    • • Shape of component cells - e.g. flat (squamous), cuboidal, columnar
    • • Presence of surface specializations - e.g. ciliated, keratinized
    • • Variations - pseudostrafied, transitional
  13. Simple Squamous Epithelia
    • • Simple squamous – flat, sometimes hard to see
    • • Lines vascular system (endothelium) and cavities (mesothelium)
    • • Also found in Bowman’s capsule of kidney and alveoli of lung
    • Function: diffusion
  14. Simple Columnar cells
    • Columnar cells are usually found in tissue in which absorption is a major function
    • Intestines, gall bladder lining (nucleus polarized to the base of the cell)
    • Lines other salivary gland ducts, and inner enamel epithelium
    • Can be polarized meaning the top of the cell is different than the bottom of the cell.
    • Allows for different type of transport through the cell.
  15. Simple Cuboidal Cell
    - Lines ducts of various glands (salivary gland ducts), kidney tubules, covers ovaries
  16. Pseudostratified Epithelium
    • • Many layers of cells but all cells rest on BM—not all cells reach surface
    • • Found in respiratory system (trachea) and male reproductive tract.
  17. Pseudostratified columnar ciliated epithelium (brochial ET)
    • • All cells rest on the basement membrane
    • • Nuclei polarized
    • • Surface is ciliated
    • • Lines the respiratory tract
    • • Also known as respiratory epithelium
  18. Stratified Squamous Epithelia
    • • Many layers of cells with basal cells cuboidal; upper layers are squamous
    • • Can be keratinized upper layers forming cornified or dry non-nucleated cells
    • • In wet mucosal tissue, tissue is non- keratinized
    • - Lines Epidermis layer of skin
    • - Lines mouth, vagina, anal, esophagus, pharynx
    • (oral) Functions to protect and withstand abrasion
    • Oral epithelium is several layers thick, but varies in the number of layers in different parts of the mouth.
  19. Simple Columnar ET
    • Lines GI Tract, uterus, gallbladder
    • Lines other salivary gland ducts, and inner enamel epithelium
    • Unique w/ Goblet cells (secrete mucous)
  20. Stratified Cuboidal & Columnar
    • • Two or more cell layers thick with the surface cuboidal or columnar—rare
    • • Usually found at transition of a simple to a strafied epithelium
    • • Example of stratified cuboidal epithelium: duct of sweat glands
  21. Transitional Epithelium
    • Transitional – a form of stratified that lines the urinary tract.
    • Contains cells are flattened and are cuboidal; hence the name "transitional" = "stretch"
  22. Distinct phases of wound healing
    • a parade of different cell populations become “activated”
    • clot formation
    • inflammation response
    • Re-epithelialization
    • Resolution
  23. Glands
    • Develop from invaginations of epithelial surfaces
    • Secretory function
    • Types (exocrine, endocrine)
  24. Exocrine
    • glands – connect to surface by ducts
    • Simple (un-branched duct)
    • Compound (branched ductal system)
    • Secretion types
    • 1. Merocrine – secretory granules leave cell by
    • exocytosis (no loss of cellular material)
    • o Glands of the intestine, simple coiled sweat glands, complex salivary glands
    • 2. Holocrine – secretory products is shed with the entire cell contents (cell is destroyed)
    • o Simple sebaceous gland
    • 3. Apocrine – secretory product is shed with part of the apical portion of the cell.
Card Set
D1 Fall MID2