Epithelial Tissue


Introduction - from your book!

Epithelial tissues cover all body surfaces, line most internal organs, and are the major tissues of glands. Because epithelium covers organs, forms the inner lining of body cavities, and lines hollow organs, it always has a free surfaceÑone that is exposed to the outside or to an open space internally.


 

Epithelial tissues are named according to two different systems:

cell shape (squamous, cuboidal, etc..)

and cell organization (simple, stratified, and pseudostratified).


Look at the cells at the blue arrow

Cell Shape - Squamous

Cell Organization - Simple

The blue arrow is pointing to a squamous cell - it is just one layer thick - therfore it could be called "simple squamous epithelium."

FYI: This tissue can be found in your kidney. What organ system include the kidneys?


Look at the cells at the black arrow (top of the picture).

Cell Shape - Squamous

Cell Organization - Stratified

The black arrow is pointing to a squamous cells that are layerd - therfore they can be called "stratified squamous epithelium."

FYI: The black cells have also been keratinized - therefore, where do these cells originate? What does it mean to be "keratinized/"


Here is another picture of stratified squamous epithelium (black arrows). This picture is from a lip.

Just in case you were wondering, the red arrows are pointing to tiny blood vessels.


Look at the cells at the two black arrows - each is pointing to a layer of cuboidal cells.

Cell Shape - Cuboidal

Cell Organization - Stratified

This specific tissue is therefore called statified coboidal epithelium.

This is a picture of a duct.


Look at the cells at the black arrow.

Cell Shape - Columnar

Cell Organization - Simple

Therefor: simple columnar epithelium. This picture is from a gall bladder.

 

FYI: The red arrow is pointing to red blood cells (erythrocytes).


 

Look at the dark cells - there is lots of stuff going on here!

First - the cells have a columnar shape, and they are pseudostratified. (If you don't know what pseudostratified means, go back and look it up in your book!)

Cell Shape - Columnar

Cell Organization - Simple

Second: the cells are also ciliated (you should know what ciliated means!)

Therefore: ciliated pseudostratified columnar epithelium. This picture is from a trachea.

And if that was not enough, there are also goblet cells in the above image! Can you find them?


These cells (black arrows) can stretch! Therefore they are called transitional epithelium.

Transitional epithelium can be found in organs that can stretch, such as your bladder.

 

 


 

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