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What are the four basic tissue types?

Epithelial tissue
Supporting tissue
Muscular tissue
Nervous tissue


What are epithelial tissues?

A diverse group of tissues including surface epithelia and solid organs


What exactly do surface epithelium cover?

All body surfaces, cavities and tubes and are therefore the interface between different compartments


What is the function of surface epithelium?

Containment, selective diffusion, absorption, secretion and physical protection


What is cytokeratin and what is it involved in?

Cytokeratin is present in all epithelial cells as an intermediate filament and allows for recognition by immunohistochemistry


All epithelium are supported by a...

basement membrane


What does the basement membrane do?

Separates the epithelium from the underlying supporting tissue


Blood vessels never cross epithelial basement membranes so how do epithelial cells obtain their needs?

They are dependent on diffusion of nutrients and oxygen from connective tissue for survial


Epithelial cells are polarised, what does this mean?

One side faces the basement membrane and one side is towards the surface


What is the side of the epithelial cell that faces the BM called and what is the side of the epithelial cell that faces the surface called?

The basal surface and the apical surface


Epithelial cells are classified according to three morphological characteristics, what are these?

1. Number of cell layers
2. Shape of component cells
3. Presence of surface specialisations


When epithelial cells are classified according to the number of cell layers, what does this mean?

They can either be simple which means they consist of one layer or they can be stratified which means they are multilayered


When epithelial cells are classified according to the shape of the component cells what does this mean?

Based on appearance at right angles to the epithelial surface. They can be squamous, cuboidal or columnar - simple epithelia. In stratified the surface shape determines the name


When epithelial cells are classified according to the presence of surface specialisations what does this mean?

It means the presence of specialisations such as cilia / keratin


There are different types of simple epithelia, list them.

1. Simple squamous epithelium
2. Simple cuboidal epithelium
3. Simple columnar
4. Pseudostratified columnar ciliated epithelium


Describe the structure of simple squamous epithelium

Flattened, irregular shaped cells forming a continuous surface often called pavemented epithelium


Where are simple squamous epithelium found and why?

Found as lining surfaces involved in diffusion of gases .g. lungs or fluids e.g. blood capillaries


Sometimes simple squamous epithelial cells are difficult to recognise because they are too flattened. How do they sometimes show up under the microscope?

They can only be recognised by the nucleus which bulges into the lumen


What are simple cuboidal epithelial cells?

They are the intermediate between simple squamous and simple columnar


Describe the nucleus in a simple cuboidal cell.

Round and located in the centre of the cell


Where are simple cuboidal epithelium cells found and what functions do they play? Give an example

Line small ducts and may have excretory, secretory or absorptive functions, e.g. collecting tubules of kidney


The cell borders in simple cuboidal cells are often indistinct so how would you be able to recognise these cells under a microscope?

The nuclei gives a clue to the cell shape, the nucleus is round and located in the centre of the cell


Describe simple columnar epithelial cells

They are like cuboidal cells but they are taller


Describe the nucleus in a simple columnar epithelial cell

They are elongated and may be located towards the base, apex or centre of the cytoplasm


Where are simple columnar epithelial cells found and give examples?

On absorptive surfaces e.g. small intestine, gall bladder (absorbs water)
or play a secretory role, e.g. the stomach


Explain why the pseudostratified columnar ciliated epithelium are considered to be a true simple epithelium

All the cells rest on the basement membrane. The nuclei are all at different levels giving the appearance of different cell layers.


Where are pseudostratified columnar ciliated epithelium found?

Confined to airways so known as respiratory epithelium.


The pseudostratified columnar ciliated epithelium have cilia on them which propel the mucus to the pharynx, what is the term applied to this?

Mucociliary escalator


What are stratified epithelia?

Defined as epithelia consisting of two or more layers


What is the main function of stratified epithelia?

Mainly a protective function