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Molecular BIO > 31. Stem Cells And Tissue Renewal > Flashcards

31. Stem Cells And Tissue Renewal Flashcards

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1
Q

Are stem cells tissue specific?

A

Yes

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2
Q

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

A
  1. Asymmetric division

2. Independent choice

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3
Q

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

A

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

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4
Q

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

A

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

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5
Q

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

A

Unable to explain how stem cells rapidly increase their numbers

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6
Q

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

A

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

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7
Q

What are founder stem cells?

A

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

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8
Q

What ultimately controls the size of a final structure?

A

The number of founder stem cells present in that tissue.

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9
Q

What is a unique feature of the founder stem cells?

A
  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
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10
Q

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

A
  1. Retain due to slow division rate

2. Taken into the cell during S phase of cell cycle

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11
Q

What is the epidermis?

A
  1. Outer skin layer
  2. Water barrier
  3. Epithelial cells. Continuously repaired and renewed
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12
Q

What is the dermis?

A

2m layer of collagen, provides toughness to skin

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13
Q

What is the hypodermis?

A

Fatty SubQ layer

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14
Q

What provides teh skin with mechanical support?

A

Extracellular matrix secreted by the fibroblasts

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15
Q

What components of the skin remove waste products?

A

Blood vessels and endothelial cells

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16
Q

Which cells provide defense against microbes and pathogens?

A

Dendritic cells and macrophages

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17
Q

What cells form the epidermis?

A

Stratified keratinocytes

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18
Q

What are the only dividing cells located in the epidermis?

A

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

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19
Q

What are the layers of cells from deep to superficial?

A
  1. Basal lamina
  2. Basal cell layer
  3. Prickle cell layer
  4. Granular cell layer
    5 keratinized squamous epithelium
20
Q

What are teh characteristic features of prickle cells?

A

Multiple desmosomes that attach tufts of keratin filaments

21
Q

What is characteristic of the granular cells?

A

Seal together to form the waterproof barrier

22
Q

What boundary do teh granular cells form?

A

Boundary between the inner metabolically active strata and the dead epidermis

23
Q

What is the outermost layer of epidermis?

A

Squame: flattened dead cells packed with keratin but no organelles

24
Q

What are the characteristics of stem cells?

A
  1. Not terminally differentiated
  2. Divide without limits
  3. Undergo slow division
  4. Provides one stem cell and one with ability to differentiate
25
Q

How does the epidermis renew itself?

A

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

26
Q

How often are the epidermis cells replaced?

A

Once every month

27
Q

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

A
  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
Q

Where does a hair follicle grow up from?

A
  1. Dermal papilla
29
Q

What is sebum?

A
  1. Oily liquid secreted from the sebaceous gland
30
Q

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

A

Beta-1 integrin subunit

31
Q

Where do transit amplifying cells come from?

A

Basal layer and incorporate into higher layers

32
Q

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

A
  1. Transit amplifying cells
33
Q

What are transit amplifying cells used for?

A

To control growth

34
Q

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

A
  1. Rate of stem cell division
  2. Rate of transit amplifying cells division
  3. Migration rate from basal layer to differentiated state
35
Q

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

A
  1. Contact with the basal lamina, via beta-1 integrin.
36
Q

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

A
  1. Increase chances of epidermal cancer development
37
Q

What happens if the hedgehog pathway becomes overactive?

A
  1. Cells continue to divide after leaving the basal layer. Overproduction of improper cells
38
Q

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

A
  1. Reduced function or presence of sebaceous glands
39
Q

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

A
  1. Extra hair follicle develop, can form tumors
40
Q

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

A
  1. No hair follicle development
41
Q

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

A

Stem cell population will be dramatically decreased

42
Q

What happens if Notch is released in too low amounts?

A

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

43
Q

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

A
  1. TGF-beta
44
Q

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

A

Promotes skin wound repair.

45
Q

What is the role of Wnt signaling pathway?

A

Controls the formation of hair follicles.

46
Q

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

A
  1. Controlling the sebaceous gland formation.

Molecular BIO (24 decks)

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