31. Stem Cells And Tissue Renewal Flashcards Preview

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Flashcards in 31. Stem Cells And Tissue Renewal Deck (46):
1

Are stem cells tissue specific?

Yes

2

How are stem cells maintained throughout the life of an organism?

1. Asymmetric division
2. Independent choice

3

How can asymmetric division provide stem cells teh ability to maintain through out a lifetime?

2 cells are created. One has stem cell characteristics and the other has the ability to differentiate

4

How can independent choice provide stem cells the ability to maintain existence throughout lifetime?

The division has 2 identical cells for but the outcome is influenced by the environment

5

What is one drawback of teh asymmetric division theory of stem cell proliferation?

Unable to explain how stem cells rapidly increase their numbers

6

Why is the independent choice more highly supported as the theory for stem cell proliferation?

More flexible and more able to explain the rapid increase of stem cells. The environment can influence how many cells are able to differentiate or remain as stem cells

7

What are founder stem cells?

Cells in a tissue with a fixed number of founder stem cells that are programmed to undergo a set number of divisions

8

What ultimately controls the size of a final structure?

The number of founder stem cells present in that tissue.

9

What is a unique feature of the founder stem cells?

1. They are established early in development.
2. Have a set number in each tissue that will grow and divide for a finite amount of time until they reach/fulfill the size of their final structure

10

Why do stem cells retain BrdU label and when is this label taken into the cell??

1. Retain due to slow division rate
2. Taken into the cell during S phase of cell cycle

11

What is the epidermis?

1. Outer skin layer
2. Water barrier
3. Epithelial cells. Continuously repaired and renewed

12

What is the dermis?

2m layer of collagen, provides toughness to skin

13

What is the hypodermis?

Fatty SubQ layer

14

What provides teh skin with mechanical support?

Extracellular matrix secreted by the fibroblasts

15

What components of the skin remove waste products?

Blood vessels and endothelial cells

16

Which cells provide defense against microbes and pathogens?

Dendritic cells and macrophages

17

What cells form the epidermis?

Stratified keratinocytes

18

What are the only dividing cells located in the epidermis?

The basal cell layer, which are attached to the basal lamina

19

What are the layers of cells from deep to superficial?

1. Basal lamina
2. Basal cell layer
3. Prickle cell layer
4. Granular cell layer
5 keratinized squamous epithelium

20

What are teh characteristic features of prickle cells?

Multiple desmosomes that attach tufts of keratin filaments

21

What is characteristic of the granular cells?

Seal together to form the waterproof barrier

22

What boundary do teh granular cells form?

Boundary between the inner metabolically active strata and the dead epidermis

23

What is the outermost layer of epidermis?

Squame: flattened dead cells packed with keratin but no organelles

24

What are the characteristics of stem cells?

1. Not terminally differentiated
2. Divide without limits
3. Undergo slow division
4. Provides one stem cell and one with ability to differentiate

25

How does the epidermis renew itself?

Basal cells divide to produce new basal cells, and other cells that will migrate superficially to replace the cells from inside out

26

How often are the epidermis cells replaced?

Once every month

27

What controls the rate/initiation of basal cell division and differentiation?

1. Contact with basal lamina via beta-integrins prevents the differentiation of the basal cells.
2. Reduced beta-integrin contact allows basal cells to divide and differentiate

28

Where does a hair follicle grow up from?

1. Dermal papilla

29

What is sebum?

1. Oily liquid secreted from the sebaceous gland

30

What is the specific integrin that prevents stem cell differentiation while in contact?

Beta-1 integrin subunit

31

Where do transit amplifying cells come from?

Basal layer and incorporate into higher layers

32

What cells have finite division but originate in the basal layer and migrate to higher levels?

1. Transit amplifying cells

33

What are transit amplifying cells used for?

To control growth

34

What are the factors that control the rate of epidermis renewal?

1. Rate of stem cell division
2. Rate of transit amplifying cells division
3. Migration rate from basal layer to differentiated state

35

What is the single most important signal for controlling epidermis renewal?

1. Contact with the basal lamina, via beta-1 integrin.

36

What happens if a signaling pathway is disrupted within the epidermis renewal system?

1. Increase chances of epidermal cancer development

37

What happens if the hedgehog pathway becomes overactive?

1. Cells continue to divide after leaving the basal layer. Overproduction of improper cells

38

What happens if sonic hedgehog is deficient to the epidermal layer?

1. Reduced function or presence of sebaceous glands

39

What happens when Wnt-signaling is overactive during epidermis renewal?

1. Extra hair follicle develop, can form tumors

40

What happens when Wnt-signaling is underproduced in the epidermal signaling pathways?

1. No hair follicle development

41

What happens if Notch signaling is too high in the epidermal renewal?

Stem cell population will be dramatically decreased

42

What happens if Notch is released in too low amounts?

Stem cell population is not inhibited and can overgrow=> tumor growth

43

What is the signaling molecule that promotes skin wound repair by forming a collagen rich scar?

1. TGF-beta

44

What is the role of TGF-beta in the epidermal renewal pathway?

Promotes skin wound repair.

45

What is the role of Wnt signaling pathway?

Controls the formation of hair follicles.

46

What is the role of sonic hedgehog in terms of epidermal renewal pathways?

1. Controlling the sebaceous gland formation.