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Molecular Biology Test IV > Specialized Tissues, Stem Cells and Tissue Renewal > Flashcards

Specialized Tissues, Stem Cells and Tissue Renewal Flashcards

1
Q

Describe the epidermis

A

Forms the outer covering of the skin
Creates a water barrier
Epithelial cells
Continuously repaired and renewed

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2
Q

Describe the dermis

A

Second layer, rich in collagen, provides toughness

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3
Q

Describe hypodermis

A

Fatty subcutaneous layer

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4
Q

What is the extracellular matrix secreted by?

A

fibroblasts and it provides the mechanical support

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5
Q

What are blood vessels lined with?

A

endothelial cells

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6
Q

What provides defense against microbes and pathogens?

A

Macrophages and DCs

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7
Q

What provides adaptive immune response?

A

lymphocytes

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8
Q

The epidermis is a ______ layer made up of ______.

A

Stratified

Keratinocytes

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9
Q

What layer is attached to basal lamina?

A

Basal cell layer

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10
Q

What are the only dividing cells in the epidermis?

A

Basal cell layer

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11
Q

In the epidermis, The strata made of several layers of prickle cells have numerous what?

A

desmosomes that attach tufts of keratin filaments

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12
Q

In the epidermis, the layer with granular cells are sealed together to form what?

A

Waterproof barrier

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13
Q

In the epidermis, what does the granule cell layer form a boundary between?

A

Inner metabolically active strata and outer dead epidermis cells

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14
Q

What is the outermost layer of the epidermis called?

A

Squame, Flattened dead cells densely packed with keratin but with no organelles

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15
Q

Basal cells are ____ cells

A

dividing

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16
Q

While some basal cells divide and maintain the basal cell layers, others do what?

A

Move to the layers above it

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17
Q

What layers above do the basal cells reach?

A

First prickle cell layer and then granule cell layer

They change in gene expression at each step of differentiation

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18
Q

As basal cells migrate to the top of the epidermis, what changes do they undergo?

A

Start undergoing partial degradation. Cells lose their nucleus and other organelles.
Dependent on partial activation of the apoptotic machinery

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19
Q

What cells provide an indefinite supply of fresh differentiated cells?

A

Stem cells
They replace and renew old cells
The basal layer has stem cells
*they divide to maintain the basal layer and also supply cells to the other layers

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20
Q

The hair follicle is a specialization of the epidermis and the hair grows upward from what?

A

Dermal papilla (connective tissue)

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21
Q

What secretes oily liquids?

A

Sebaceous glands

22
Q

What is the oily liquid sebaceous glands secrete?

A

Sebum

23
Q

What cycle does a hair follicle undergo?

A

Growth, regression, and reconstruction

24
Q

What is present in a bulge to help in reconstruction and gives rise to hair follicle and interfollicular epidermis?

A

Stem cells

25
Q

What are characteristics of stem cells?

A

Not terminally differentiated
Can divide without limit
Undergo slow division
When it divides it gives rise to 1 cell with stem cell characteristics and the other with the ability to be differentiated

26
Q

Stem cells are tissue ______.

A

specific

27
Q

How is a steady pool of stem cell population accomplished?

A

Divisional Asymmetry-asymmetric division may create 2 cells, one with stem cell characteristics and another with the ability to differentiate
Environmental Asymmetry - Division makes 2 identical cells but environment may influence/alter 1 cell

28
Q

What is the issue with divisional Asymmetry?

A

Has draw backs

Cannot explain how existing stem cells increase their numbers

29
Q

Why is environmental asymmetry a more plausible theory?

A

It is more flexible. Explains the sharp increase in stem cell numbers when needed for repair
Environment may influence batches of cells and does not have to be 50:50 for every division

30
Q

Contact with what controls the numbers of stem cells?

A

Basal lamina

*maintenance of contact preserves stem cell potential

31
Q

What does loss of contact of the epidermis with the basal lamina trigger?

A

terminal differentiation

32
Q

What does proliferative potential of stem cells directly correlate with?

A

Expression of Beta1 subunit of integrin (helps mediate adhesion to the basal lamina)

33
Q

Clusters of cells with high levels of integrin are found where in the epidermis?

A

Near the basal lamina and in the bulge of hair follicle

34
Q

Mixed with stem cells are other cells that divide frequently, what are these cells called?

A

Transit amplifying cells

35
Q

Where do transit amplifying cells transit from?

A

Transit from A cell with stem cell characteristics to a differentiated cell. Leaves the basal layer and are incorporated into the layers above

36
Q

Can transit amplifying cells divide an unlimited amount of times?

A

No they are programmed to divide for a limited number of times. Part of a strategy for growth control

37
Q

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

A

Founder

38
Q

What are founder stem cells controlled by?

A

Short range signals that operate for a few hundred cell diameters

39
Q

If the adult organ needs to be renewed, Founder stem cells can divide as what?

A

as stem cells giving rise to one daughter cell that remains a stem cell and a set of cells that have a set number of transit amplifying divisions

40
Q

What is taken up by cells in the S phase of cell cycle that allows the daughter cell to retain stem cell characteristics?

A

BrdU label

41
Q

______ cells retain BrdU label for a long time

A

Stem

  • could be due to slow rate of division
  • also could be due to asymmetric segregation of their DNA
42
Q

After division, what happens to the BrdU label?

A

One of the daughter cells gets ALL the original DNA strands from the chromosomes including the BrdU label and this daughter cell will retain stem cell characteristics

43
Q

The original strand of DNA is preserved in stem cells from generation to generation. Second cell gets the newly synthesized strand. This is a way to prevent what?

A

Genetic errors in stem cells

44
Q

What are factors governing renewal of epidermis?

A

Rate of stem cell division
Probability that one of the daughter cells will remain a stem cell
Rate of division of the transit amplifying cells
Timing of exit from basal layer and the time the cell takes to differentiate and be sloughed away from surface

45
Q

What is the most important signal for regulating of epidermis renewal?

A

Contact with basal lamina most important signal
Mediated via integrin signaling
Helps control size of stem cell population
Loss of contact abolishes stem cell characteristics and promotes formation of cells that can become differentiated

46
Q

Overactivation of ______ pathway makes cell continue to divide even after exit from basal layer.

A

Hedgehog

47
Q

Deficit of hedgehog signal leads to what?

A

loss of sebaceous glands

48
Q

Up-regulation of ____ signaling causes extra hair follicles to develop (give rise to tumors)

A

Wnt

49
Q

Loss of Wnt signaling leads to what?

A

Failure of hair follicle development

50
Q

What restricts size of stem cell population?

A

Notch signaling

51
Q

Lateral inhibition causes neighbors of stem cells to become what?

A

Transit amplifying cells

52
Q

What plays a key role in repair of skin wounds promoting formation of collagen rich scar tissue?

A

TFGBeta

Molecular Biology Test IV (6 decks)

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