3.1 Epithelial Tissues

Question 1

What are the 4 primary tissue classes?

Answer 1

1. epithelial tissue
2. connective tissue
3. nervous tissue
4. muscular tissue

Question 2

What are the 4 cell junctions of epithelial tissues?

Answer 2

1. desmosomes
2. hemidesmosomes
3. tight junctions
4. gap junctions

Question 3

What are desmosomes?

Answer 3

they are found between cells (proteinaceous plaque and threads)

Question 4

What are hemidesmosomes?

Answer 4

they anchor cells into the basement membrane

Question 5

What are tight junctions?

Answer 5

they hold and pack cells together (like plastic wrap on a 6-pack of cans)

Question 6

What are gap junctions?

Answer 6

• they are the only communicating cell connections

- they are especially rich in smooth and cardiac muscles

Question 7

What are the 3 functions of epithelial tissues?

Answer 7

1. protection (dermis)
2. secretion (glands)
3. absorption (microvilli)

Question 8

What are the 3 different layers of epithelial tissues?

Answer 8

1. simple/pseudostratified
2. stratified
3. transitional

Question 9

What are the basic types/shapes of epithelial tissues?

Answer 9

1. squamous (flat)
2. cuboidal (nucleus is round and center of the cell)
3. columnar (nucleus is elliptical and near base of the cell)
4. transitional (transitions between squamous and cuboidal)

Question 10

What does epithelial tissue look like?

Answer 10

1. apical surface
2. lateral surfaces
3. basal surface
4. basement membrane (basal lamina + reticular lamina + hemidesmosomes)
5. connective tissue

Question 11

How are tissues prepared?

Answer 11

• dehydrated and defatted, accomplished with changes of xylene and alcohol (“fixation”)
• embedded in paraffin blocks and sectioned into thin sections by histotechnologists
• slides commonly stianed with Hemotoxylin (purplish-blue) and Eosin (orange-pink)

Question 12

1. What are the 3 characteristics of simple squamous epithelium?

Answer 12

1. flattened cells, squashed, “fried eggs”
2. thin layers allow diffusion and osmosis
3. locations: alveoli, lining of blood vessels (endothelium)

Question 13

2. What are the 2 characteristics of simple cuboidal epithelium?

Answer 13

1. single layer of cube-shaped cells; nucleus is round and centered. Cells are arranged in a circle around the lumen
2. locations that are ducts: glands - pancreas, thyroid, salivary glands

Question 14

3. What are the 4 characteristics of simple columnar epithelium?

Answer 14

1. column-shaped cells; elliptical nuclei near the base.
2. goblet cells make mucus (protection)
3. microvilli extant on cells of the GI tract; none on goblet cells –> increased absorptive surface area
4. no blood vessels in the epithelium layer
5. locations that have microvilli and needed for absorption: stomach, small intestine, gallbladder

Question 15

4. What are the 4 characteristics of simple columnar CILIATED epithelium?

Answer 15

1. ciliated column-shaped cells; elliptical nuclei near the base
2. goblet cells make mucus (protection)
3. cilia wave substances across surface (such as eggs in fallopian tubes)
4. locations: fallopian tubes, ovaries (female reproductive tract)

Question 16

5. What are the 4 characteristics of pseudostratified CILIATED columnar epithelium?

Answer 16

1. ciliated column-shaped cells; elliptical nuclei near the base. Looks stratified but each cell makes contact with the basement membrane
2. goblet cells make mucus (protection)
3. cilia wave substances across surface (from deep in lungs, out). If damaged, will be replaced with squamous keratinized - why?
4. locations: trachea and bronchioles

Question 17

6. What are the 3 characteristics of transitional epithelium?

Answer 17

1. transitions between simple & stratified arrangement, and between cuboidal/dome-shaped to squamous/flattened cells
2. the ONLY epithelium that is binucleate; other binucleate epithelia would be considered malignant
3. locations: lines urinary bladdar and ureters

Question 18

7. What are the 4 characteristics of stratified squamous non-keratinized epithelium?

Answer 18

1. layered squamous cells
2. diffusion and osmosis is difficult
3. upper layers will slough off
4. locations that can withstand desiccation: lines mouth, vaginal canal, cervix

Question 19

8. What are the characteristics of stratified cuboidal epithelium?

Answer 19

locations for a more robust lining: exocrine glands (salivary glands)