L5. Epithelium

Question 1

What are tissues?

Answer 1

Tissues are a set of morphologically similar cells that perform a function or a set of functions

Question 2

What are the characteristics of epithelial tissues?

Answer 2

1. Avascular ( no blood vessels)
2. A group of continuous group of cells
3. Are defined basally and apically. With basal end attached to the basement membrane. Apical end is the lumen formation
4. There is no ECM between the cells
5. Cells are attached to the basement membrane (ECM)

Question 3

What are the 4 functions of the epithelial tissues?

Answer 3

1.protect underlying tissues
2.involved in the secretion of substances
(paracrine, endocrine, exocrine)
3.involved in the transport of substances
4.absorb substances ( usually have specialized structures)

Question 4

What are the 2 types of transport (cellular)

Answer 4

1. transcellular transport: involves the use of channels such that substances flow through these channels into the cell
2. paracellular: substances flow between the cells at junctions without the tight junctions (adhesion is not tight)

Question 5

What are the 3 forms of secretion

Answer 5

1. paracrine: substances secreted basally into the BM of the ECM
2. endocrine: substances are secreted basally into the BM of the ECM can eventually enter the bloodstream
3. exocrine: secreted apically into the lumen into the external environment

Question 6

How are lumens form?

Answer 6

Through the constriction of the apical zonular belt.
induces tubular morphogenesis
shape change

Question 7

What causes the shape change during tubular formation

Answer 7

actin-myosin facilitates the contraction of the apical zonular belt.

Question 8

What are the specialized apical structures?

Answer 8

1. microvilli

2. cilia

Question 9

Describe the microvilli

Answer 9

1. can be seen as a brush border on the LM.
2. can be resolved with the EM
3. increases the SA makes absorption more efficient
4. bundles of actin filament
5. non-motile
6. 1 um long 25nm wide

Question 10

What is the dimensions of the microvilli

Answer 10

1um long 25nm wide

Question 11

Describe the cilia

Answer 11

1. facilitates in cell movement; motile
2. 10um long, 250nm wide
3. core of microtubules arranged in radial spokes
4. individual structure seen on both LM and EM

Question 12

What are the categories of cell layers?

Answer 12

1. simple: only 1 layer all cells attached to BM
2. stratified: multilayer ( see many nuclei down the vertical)
3. pseudostratified: looks stratified ( many nuclei) irregularly shaped cells but all cells are attached to BM

Question 13

What are the categories of cell shape?

Answer 13

1. squamous: flattened
2. cuboidal: looks like a cube
3. columnar: looks wider by the sides

Question 14

What are the different cell structures?

Answer 14

1. simple squamous epithelium
2. simple cubodial
3. simple columnar
4. stratified (keratinized) squamous
5. stratified (not keratinized) squamous
6. pseudostratified
7. transitional

Question 15

Functions of simple squamous epithelium

Answer 15

• lining epithelium
• lubrication
• located at sites for fluid and gas exchange

Question 16

What structures have a simple squamous epithelium

Answer 16

blood and lymphatic vessels
loop of Henle
lining of internal body
thoracic cavity

Question 17

Functions of simple cubodial epithelium

Answer 17

absorption
secretion
protection

Question 18

What structures have a simple cubodial epithelium

Answer 18

tubules of kidney

ducts of glands

Question 19

Functions/Features of simple columnar epithelium

Answer 19

absorption
secretion
transportation
- have an apical brush border

Question 20

What structures have a simple columnar epithelium

Answer 20

found in gastrourinary tract and the digestive system

Question 21

Functions/Features of stratified squamous (keratinized) epithelium

Answer 21

• protective
• waterproof
• has a layer of dead cells (enucleated)
• filled with keratin intermediate filaments
• has hemidesosomes

Question 22

Functions/Features of stratified squamous (un-keratinized) epithelium

Answer 22

• protective
• many layers
• no layers of dead cells
• only basal layer attaches to the BM

Question 23

What structures have a stratified squamous (keratinized) epithelium

Answer 23

outer layer of the skin

Question 24

What structures have a stratified squamous (un-keratinized) epithelium

Answer 24

found in wet areas of the external/ internal transition of the GI, respiratory and geniuritonary tracts

• mouth
• larynx
• vagina
• anal cavity
• esophagus
• urethra

Question 25

Functions/Features of pseudostratified

Answer 25

absorption
secretion
lubrication 
protective
cells are of different height 
all cells attached to the BM
often ciliated

Question 26

What structures have pseudostratified epithelium

Answer 26

trachea
primary bronchi 
nasal cavity 
epididymis
vas deferens

Question 27

What structures have transitional epithelium

Answer 27

-bladder

Question 28

Functions/Features of transitional epithelium

Answer 28

stratified and distensible
when relaxed: cubodial
when stretched: squamous

Question 29

(Draw for me tubular morphogenesis)

Answer 29

L5 pg 4a.

Question 30

What adhesion protein is used in tubular morphogenesis?

Answer 30

zonular adherins

Question 31

what cytoskeleton is involved in tubular morphogenesis

Answer 31

actin filament