Epithelia

Question 1

What are the functions of the epithelium (5)?

Answer 1

Protection, absorption, secretion, contractility, sensory

Question 2

Describe Microvilli

Answer 2

to increase surface area for secretion/absorption. made with actin filaments and anchored by villin. TW can move to expose them to new environment but they cannot move themselves.

Question 3

Describe mobile cilia

Answer 3

made with microtubule cores in 9+2 doublets, use dynein to bend to one side and then passively snap back into place. Useful for moving things along apical surface. much larger than microvilli. stem from basal body MTOC.

Question 4

What are some places you might find motile cilia?

Answer 4

respiratory tract, uterine tract, ventricles, middle ear cavity

Question 5

Describe primary cilia.

Answer 5

these are sensory cilia, still composed of MTs, but with a 9+0 conformation, so they cannot move. usually they are only 1/cell.

Question 6

What are some functions for primary cilia?

Answer 6

Sensory. Also important for establish a left/right plane in early gestation.

Question 7

Describe flagella. Where might one be found?

Answer 7

Flagella is an extremely long cilia used for transportation. Found on sperm. there is only 1/cell. They have the classic 9+2 setup with extensive mitochondria.

Question 8

What are stereocillia? Where are they found?

Answer 8

Misnomer- they are actually long microvilli and form the sensory hairs of the inner ear.

Question 9

What are the 4 junctions found on the lateral side?

Answer 9

Tight junction (zonula occludens), adherent junction (zonula adherens), desmosome (macula adherens) and gap junctions

Question 10

Describe tight junctions.

Answer 10

Go all the way around the cell, most apical junction. Formed by connections between claudin and occluden proteins. Regulate paracellular pathway (between cells) and provides diffusion barrier for cellular proteins.

Question 11

Describe adherent junctions

Answer 11

Formed by cadherin proteins and attached to actin filaments, they connect the terminal webs of adjacent cells

Question 12

What does cadherin do?

Answer 12

Found in adherent junction and desmosome, forms linkage between adjacent cells

Question 13

What does claudin do?

Answer 13

one of the linking proteins in tight junctions

Question 14

What does occludin do?

Answer 14

one of the linking proteins in tight junctions

Question 15

Describe desmosomes.

Answer 15

Spotweld junctions. cadherins bind to IFs and provide significant structural connection between adjacent cells. These are the strongest connections

Question 16

Describe gap junctions

Answer 16

Proteins called connexins group together in sets of 6 to form connexons which forms the pore in gap junctions. One gap junction has 100s of pores and allows the passage of small ions

Question 17

Describe the basal membrane.

Answer 17

All epithelia grow on a basement membrane. it contains no cells, but instead is made of type 4 collage, fibronectin, laminin, proteoglycans, and enactin

Question 18

What are the functions of the basal membrane (4)?

Answer 18

1. limits growth
2. allows diffusion
3. provides structure for growth
4. provides signaling

Question 19

What does fibronectin do?

Answer 19

It is a protein found in the basement membrane

Question 20

What does laminin do?

Answer 20

it is a protein found in the basement membrane.

Question 21

What does enactin do?

Answer 21

it is a protein found in the basement membrane.

Question 22

List the specializations of the basal membrane

Answer 22

hemidesmosome and focal adherens

Question 23

Describe the hemidesmosome.

Answer 23

Integrin froms a connection between the laminin and fibronectin and the IFs of the cell to secure them to the basement membrane

Question 24

Describe the focal adherens.

Answer 24

Intergin forms a connection between actin and laminin and fibronectin.

Question 25

Where might you find simple squamous cells?

Answer 25

blood vessels or mesentaries of organs

Question 26

Where might you find simple cuboidal cells?

Answer 26

kidney tubules or ducts

Question 27

Where might you find simple columnar with microvilli?

Answer 27

Intestines

Question 28

Where might you find simple columnar with cilia?

Answer 28

respiratory tract

Question 29

where might you find pseudostratified cells?

Answer 29

upper respiratory tract- always have cilia

Question 30

where might you find non-keratinized stratified squamous cells?

Answer 30

esophogus or vagina

Question 31

where might you find stratified squamous keratinized cells?

Answer 31

skin

Question 32

What is the benefit of keratinizing cells?

Answer 32

It prevents water loss

Question 33

Where might you find stratified cuboidal?

Answer 33

sweat glands

Question 34

What are urothelium cells and where might you find them?

Answer 34

They appear rounded on top because they are made to stretch. They can be found in the urinary tract.

Question 35

What is metaplasia?

Answer 35

When cells are exposed to stressors, they can change their type (ie squamous to columnar) to adapt. However, this flexibility makes them more susceptible to cancers (carcinomas)

Question 36

What is an exocrine gland?

Answer 36

secretes to the surface of the epithelia

Question 37

What is an example of a unicellular gland?

Answer 37

Goblet cell- secretes mucus. Found in respiratory and intestinal tracts.

Question 38

What is the difference between a compound and simple gland.

Answer 38

simple glands have a 1 duct / 1 gland ratio. Compound glands have many more glands/ 1 duct.

Question 39

Difference between tubular and acinar glands?

Answer 39

tubular are like tubes, acinar is like a circle (also called alveoli)

Question 40

What are the 3 secretion mechanisms and how do they differ?

Answer 40

holocrine- entire contents of cell
apocrine- secreted in vesicles- more lipids b/c of membrane
merocrine- secreted without the vesicle- most common

Question 41

How can you tell the difference between mucous and serous secretions?

Answer 41

Mucous are clear on stains because they have no proteins, serous are dark because the proteins within them stains.

Question 42

What are the three sides of epithelia?

Answer 42

apical (towards environment), lateral, basal (away from environment)