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Molecular Biology Exam 3 > Specialized Tissues, Stem Cells, and Tissue Renewal I: Maintenance and Renewal of Skin > Flashcards

Specialized Tissues, Stem Cells, and Tissue Renewal I: Maintenance and Renewal of Skin Flashcards

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1
Q

What are the characteristics of stem cells?

A
  • Not terminally differentiated.
  • Can divide without limit.
  • Undergo slow division.
  • When divide gives rise to 1 cell with stem cell characteristics and the other with the ability to be differentiated.
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2
Q

True or False:

Stem cells are tissue specific.

A

True

(e.g., epidermal stem cells, intestinal stem cells, etc…)

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3
Q

In the maintenance of stem cells, how is a steady pool of stem cell population remained?

A

Precisely 50% of daughter cells must remain as stem cells.

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4
Q

In the maintenance of stem cells, what is asymmetric division?

A

Creates 2 cells:

  • one with stem cell characteristics
  • another with the ability to differentiate
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5
Q

In the maintenance of stem cells, what is independent choice?

A

Division makes 2 identical cells but the outcome is stochastic and/or influenced by the environment.

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6
Q

This type of division creates 2 cells, one with stem cell characteristics and another with the ability to differentiate?

A

Asymmetric Division

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7
Q

What is the term given to a stem cell division that makes 2 identical cells but the outcome is stochastic and/or influenced by environment?

A

Independent Choice

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8
Q

What is the drawback to the asymmetric division hypothesis?

A

Cannot explain how existing stem cells increase their numbers.

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9
Q

What can the independent choice hypothesis explain?

A

Explains the sharp increase in stem cell numbers when needed for repair.

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10
Q

Which of the hypotheses, asymmetric division or independent choice, is more flexible?

A

Independent choice is more flexible.

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11
Q

True or False:

In the maintenance of stem cells, environment may influence batches of cells and does not have to be 50:50 for every division.

A

True

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12
Q

True or False:

Each organ/tissue has fixed number of founder cell populations programmed to have fixed number of divisions.

A

True

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13
Q

What are founder cell populations programmed to have?

A

A fixed number of divisions.

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14
Q

What controls founder stem cells?

A

Short range signals that operate for a few hundred cell diameters.

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15
Q

What do founder stem cells define the size of?

A

Large final structures (organ/tissues).

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16
Q

Does each organ/tissue have a fixed number of founder stem cells?

A

Yes

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17
Q

True or False:

Short-range signals determine founder stem-cell populations during development.

A

True

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18
Q

True or False:

Founder stem-cell populations stay small and transit amplifying divisions let them generate and renew a big adult structure.

A

True

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19
Q

In which phase of the cell cycle do cells take up BrdU label?

A

S phase of cell cycle.

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20
Q

Why do stem cells retain BrdU label for a long time?

A

> Due to slow rate of division.
Also, could be due to asymmetric segregation of their DNA.

after division one of the daughter cells gets all the original DNA strands from all the chromosomes - this daughter cell will retain stem cell characteristics

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21
Q

What is a way to prevent genetic errors in stem cells?

A

> After division one of the daughter cells gets all the original DNA strands from all the chromosomes.

> This daughter cell will retain stem cell characteristics.

> Original strand of DNA preserved in stem cells from generation to generation.

> Second cell gets the newly synthesized strand.

this is a way to prevent genetic errors in the stem cell

this is called the - Immortal Strand Hypothesis

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22
Q

What is the hypodermis?

A

Fatty subcutaneous layer.

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23
Q

What is the dermis?

A

Second layer, rich in collagen, provides toughness.

24
Q

What is the dermis rich in?

A

collagen

25
Q

What is the epidermis?

A
  • Forms the outer covering of skin.
  • Creates a water barrier.
  • Made of epithelial cells.
  • Continuously repaired and renewed.
26
Q

Is the epidermis continuously repaired and renewed?

A

Yes

27
Q

What does the epidermis form?

A

The outer covering of skin.

28
Q

What type of cell secretes extracellular matrix and what does it provide?

A

Fibroblasts

Mechanical support

29
Q

True or False:

Blood vessels lined with endothelial cells supply nutrients and oxygen and remove waste products.

A

True

30
Q

What do macrophages and dendritic cells divide?

A

Defense against microbes and pathogens.

31
Q

What type of immunity do lymphocytes provide?

A

Adaptive Immune Response

32
Q

What do nerve fibers in the skin provide?

A

Sensory Information

33
Q

In which layer of the skin do Langerhans cell reside?

A

Epidermis

34
Q

Are lymphocytes and macrophages found in the loose connective tissue of the dermis or the dense connective tissue of the dermis?

A

Loose Connective Tissue of Dermis

35
Q

The epidermis is a stratified layer made of what type of cells?

A

keratinocytes (have keratin intermediate filaments)

36
Q

What is the basal cell layer attached to?

A

Basal lamina

37
Q

What cell layer of the epidermis is attached to the basal lamina?

A

Basal Cell Layer

38
Q

What are the only dividing cells found in the epidermis?

A

Basal Cell Layer

39
Q

What type of cells make up the next strata after the basal cell layer?

A

Several layers of prickle cells.

**which have numerous desmosomes that attach tufts of keratin filaments*

40
Q

What is the next layer after the several layers of prickle cells?

A

Layer of granular cells which are sealed together to form a waterproof barrier.

the granule cell layer forms a boundary between inner metabolically active strata and outer dead epidermis cells

41
Q

Which layer of the epidermis forms a waterproof barrier?

A

Granule cell layer, which are sealed together to form a waterproof barrier.

42
Q

What does the granule cell layer form a boundary between?

A

Inner metabolically active strata and outer dead epidermis cells.

43
Q

What is the outer layer of the epidermis called?

A

Squame

flattened dead cells densely packed with keratin but with no organelles

44
Q

What do cells in the squame not have?

A

no organelles

Outermost layer is called squame, flattened dead cells densely packed with keratin but with no organelles.

45
Q

What is the renewal of epidermis a process of?

A

Self-renewing process.

46
Q

Which cells in the epidermis are the only cells that can divide?

A

Basal cells are dividing cells.

while some basal cells divide and maintain that layer, others move to the layers above it

47
Q

Some basal cells divide and maintain that layer, but what happens to the others?

A

Others move to the layers above it - reach prickle cell layer and then the granule cell layer.

**a change in gene expression at each step of differentiation

**this cells acquire the phenotype appropriate for that layer

**cells start undergoing partial degradation

**cells lose their nucleus and other organelles

**this is dependent on partial activation of the apoptotic machinery

48
Q

What is the time from birth of cell in basal layer to shedding from the surface of the skin?

A

about 1 month

49
Q

In the renewal of the epidermis by stem cells a mixture of cells are needed, what are they?

A

Those that can divide and differentiate and renew worn out cells.

Those that can remain undifferentiated.

50
Q

In the renewal of the epidermis, what do stem cells provide?

A

Indefinite supply of fresh differentiated cells.

51
Q

In which layer of the epidermis do stem cells reside?

A

Basal Layer

52
Q

Hair grows in hair follicles. Where does hair grow upward from?

A

Dermal papilla

53
Q

What does sebaceous glands secrete?

A

Oily liquid called sebum.

54
Q

What do hair follicles undergo cycles of?

A

Growth, regression, and reconstruction.

55
Q

Where in the hair follicle are stem cells located?

A

Stem cells present in a bulge and help in reconstruction and gives rise to hair follicle and interfollicular epidermis.

56
Q

What do stem cells present in the bulge of the hair follicle help in?

A
  • reconstruction

- gives rise to hair follicle and interfollicular epidermis

57
Q

stopped on slide 25

A

keep working hard everyone

Molecular Biology Exam 3 (9 decks)

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