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Examination of Epithelial Tissue

VIEWS: 47 PAGES: 4

									Name: ___________________________________                          Period:________              Date: _____________

Examination of Epithelial Tissue

Overview
           The epithelium is the layer (or layers) of cells forming the secured boundary between a structure and its
environment. Because of the varied narutre of the organs of the body, different types of epithelial tissue can be found in
different locations. Two terms commonly used with epithelial tissue are simple and stratified. Simple means the tissue
occurs in a single layer of cells, whereas stratified means the cells are stacked in layers or strata.
The chart below gives an overview of the subdivisions of epithelial tissue.



Cell Shape                Simple                                            Stratified
Squamous                  Type: simple squamous                             Type: stratified squamous
                          Examples: mesothelia, endothelia                  Examples: surface of skin, both ends of digestive
                          Functions: reduces friction, permits              tract
                          absorption/secretion in protective environments   Function: protection
Cuboidal                  Type: simple cuboidal                             Type: stratified cuboidal
                          Examples: glands, ducts, urinary tract            Example: lining of some ducts (rare)
                          Functions: limited protection, secretion and/or   Functions: proctection, secretion and/or
                          absorption                                        absorption


                                                                            Special variation: transitional
                                                                            Examples: urinary bladder, portions of urinary
                                                                            tract
                                                                            Functions: permits expansion and contraction
Columnar                  Type: simple columnar                             Type: stratified columnar
                          Example: lining of digestive tract                Examples: large ducts and passageways of
                          Functions: protection, secretion, absorption      respiratory tract
                                                                            Function: protection
                          Special variation: pseudostratified columnar
                          Example: portions of respiratory and male
                          reproductive tracts
                          Functions: protection, secretion


Squamous Epithelium
           Squamous epithelial cells are flat and somewhat irregularly shaped. The simple squamous epithelial cells, such
as those found in the mesothelia and endothelia, occur in a single layer. The terms mesothelium and endothelium refer
to the linings of the ventral body cavity and the vascular systems, respectively.
           The stacked layers of stratified squamous epithelial cells are found on the surface of the skin and the linings of
the mouth, esophagus, and anus. Skin cells are keratinized, which makes them tough and water resistant. Keratin is the
protein that is characteristic of much of the integument. Other stratified squamous epithelial cells, such as those lining
the oral cavity, esophagus, and pharynx, are non-keratinized.


    1) Obtain and observe slide of all the types of squamous epithelium. Compare your slides with the examples in the
           lab manual after page 100.
   2) Sketch and label the two types of squamous epithelium in the spaces below.




Sample Name: _____________________              Sample Name: ______________________


   3) Why are the structures of these cells ideal for their functions? ________________________________________

      ___________________________________________________________________________________________

      ___________________________________________________________________________________________


Cuboidal Epithelium
      Cuboidal epithelial cells are generally cube-shaped cells occurring in a single layer in glands, ducts, and tubes.
      These are simple cuboidal epithelial cells. In a few ducts, such as sweat gland ducts, and the larger mammary
      gland ducts, cuboidal cells do occur in strata. These are the stratified cuboidal epithelial cells.


   1) Obtain and observe slides of both types of cuboidal epithelium. Compare your slides with the examples in the
      lab manual after page 100.
   2) Sketch and label the two types of cuboidal epithelium in the spaces below.




Sample Name: _____________________              Sample Name: ______________________


   3) Why are the structures of these cells ideal for their functions? ________________________________________

      ___________________________________________________________________________________________

      ___________________________________________________________________________________________
Columnar Epithelium
       Columnar epithelial cells are elongated rectangular cells. Simple columnar epithelial cells line the digestive
       tract while stratified columnar cells can be found in the large ducts of the respiratory tract.


   1) Obtain and observe slides of both types of columnar epithelium. Compare your slides with the examples in the
       lab manual after page 100.
   2) Sketch and label the two types of columnar epithelium in the spaces below.




Sample Name: _____________________              Sample Name: ______________________


   3) Why are the structures of these cells ideal for their functions? ________________________________________

       ___________________________________________________________________________________________

       ___________________________________________________________________________________________


Pseudostratifed Columnar Epithelium
       Pseudostratified columnar epithelial cells line the trachea and portions of the male reproductive tract. This
       tissue type is distinguished because the cells, although they appear to be stratified, all rest on a common
       boundary, the basement membrane.
   1) Refer to the examples at the end of the lab packet and identify the pseudostratifed cells by looking for the
       common border for at least two distinct rows of nuclei. The pseudostratified epithelial cells tend to be ciliated.
       Pollutants can destroy the cilia.
   2) Obtain and observe slides of pseudostratified columnar epithelium. On your slide the cilia border will probably
       appear thicker than the other cell boundaries. Depending on the stain used, the cilia may appear darker or
       lighter than the rest of the cell. The cilia border may also appear somewhat fuzzy Compare your slides with the
       examples in the lab manual after page 100.
   3) Sketch and label what you see.
    4) What is the function of the cilia on these types of epithelial cells? ______________________________________

        ___________________________________________________________________________________________

        ___________________________________________________________________________________________


Transitional Epithelium
        Transitional epithelial cells are technically classified as stratified cuboidal cells because epithelial structures are
classified according to their most external cell layer. For our purposes, however, we will continue the more
conventional “transitional” classification. These cells, which line the urinary bladder, change in appearance from their
relaxed to their stretched state.


    1) Obtain and observe slides of transitional epithelium. Compare your slides with the examples in the lab manual
        after page 100.
    2) Sketch and label what you see.




    3) What is the functional advantage of having transitional epithelial cells in the urinary bladder? ______________

        ___________________________________________________________________________________________

        ___________________________________________________________________________________________

								
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