Epithelial Cell

Epithelial Cell

1. make up primary tissues throughout the body.

2. There are many arrangements of epithelial cells

   • that organize
     • as simple
     • as pseudostratified
     • as stratified
     • as transitional

3. Epithelial cells form from

   • ectoderm
   • mesoderm
   • endoderm
   • Epithelial tissue cover most of the body and organ surfaces.

4. their function changes based on their location and morphology .

5. have a structural polarity that causes three distinct regions or domains

   • apical
     • faces the lumen of an organ or the external environment
     • is made up of this structure affects the cells function
       • microvilli
         • The number of microvilli correlates to the absorptive properties of the cell
         • are involved in fluid transport and absorption
       • cilia
         • transport substances across the surface of epithelial cells.
       • stereocilia
         • are essential in hearing and balance
   • basal
     • The basal domain is connected to the basal lamina by hemidesmosomes
     • separates connective tissue from the epithelium
   • lateral
     • connects neighboring cells and allows for communication between cells.
       • is made up of
         • Tight junctions are occluding junctions
           • that regulate the movement of fluid and solutes.
         • Gap junctions are communicating junctions
           • that create channels that allow small molecules and ions to pass between adjacent cells.

6. are organized according to their shape and number of layers

7. there are three main shapes

   • squamous
     • are flat sheet-like cells
       • lines blood vessels (endothelium)
       • allows for diffusion of molecules like in gas exchange.
       • lines body cavities (mesothelium)
   • columnar
     • are taller than they are wide making them rectangular.
       • found throughout the intestines
       • can have either an absorptive or secretory function
   • cuboidal
     • are cube-like with an equal width, height, and depth
       • have a secretory function
       • tend to form the lining of ducts.

8. Tissue Preparation

   • is possible via biopsy.
     • after a sample is collected
       • it is fixed in formalin
       • embedded in an embedding medium such as paraffin
       • sectioned
       • stained

9. Histoquímica y citoquímica

   • Epithelial cells have specialized cytoskeletons comprised
     • of microtubules
     • of actin filaments
     • intermediate filaments
       • provide structural resilience to the cytoskeleton
       • show tissue-specific expression
       • are a useful target for histochemical staining techniques
       • There are five main groups
         • neurofilaments
         • desmin filaments
         • keratin
         • Glial filaments
         • vimentin filaments

10. microscopy

    • is typically used to visualize stained epithelial cells
      • the main types
        • Light microscopy (LM)
          • can be used to determine the morphology of the epithelium
        • Electron microscopy (EM)
          • is a form of microscopy that allows a higher magnification than light microscopy (LM).
          • allows visualization of many ultrastructural features
            • tight junctions
            • adherens junctions
            • desmosomes
            • hemidesmosomes,
            • gap junctions
            • the basal lamina

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