Epithelia I

Question 1

List the characteristics of epithelia

Answer 1

1. cells adhere to one another
2. arranged in one (simple) or multiple (stratified) layers
3. Most epithelia are polarized
4. Attached to a basal lamina
5. cells undergo turn-over, are replaced by stem cells
6. highly diverse.

Question 2

List the fxns of epithelia

Answer 2

1. Create a barrier to protect internal tissues
2. selective absorption and transport of molecules
3. movement of particles and mucous through passageways
4. biochemical modifications (e.g. liver)
5. communication w/ other tissues
6. reception of sensory stimuli (olfaction and gustation)

Question 3

List the types of “special” epithelia

Answer 3

1. endothelium: modified epithelial cells lining blood and lymphatic vessels
2. mesothelium: sheets of cells lining body cavities and organs

Question 4

List the layers of epitheila from superficial to deep

Answer 4

1. apical surface of epithelial cell
2. basolateral side of epithelial cell
3. basal lamina
4. connective tissue (w/ blood vessels, muscle, and nerves)

Question 5

Define what a mucosa is and list its layers

Answer 5

Mucosae are moist epithelial tissues

1. epithelial layer
2. lamina propria (CT)
3. Submucosa (deeper CT, perhaps including muscle)

Question 6

List the classifications of epithelia

Answer 6

Based on layers:

1. simple
2. stratified
3. pseudostratified–some cells do not reach the free surface, but all cells attached to basal lamina

Based on cell shape:

1. squamous
2. cuboidal
3. columnar

Epithelia are named according to the outermost layer, with the exception being the transitional epithelia of the bladder (they change their shape when stretched).

Question 7

Describe the polarization of epithelia and the functions such polarization provides

Answer 7

Epithelial cells are polarized cells, meaning their apical and basolateral sides have different morphologies, contain different amounts of proteins and organelles.

Fxns of polarization:

1. selective and directional transport (various pumps, transporters, and transcytosis).
   - this polarity is supported by tight junctions, which disallow paracellular transport of substances.