Zaidi: Specialized Tissues, Stem Cells and Tissue Renewal

Question 1

Characteristics of stem cells

Answer 1

Not terminally differentiated
Can divide without limit
Can renew themselves
Can divide into stem cell or differentiate into different cell type
Undergo slow division

Question 2

Totipotent

Answer 2

Give rise to all cells of organism- Zygote

Question 3

Pluripotent

Answer 3

Give rise to all cells of embryo and adult tissues- Embryonic stem cells

Question 4

Multipotency

Answer 4

Give rise to different cell types of a given lineage- Adult stem cells

Question 5

Asymmetric division

Answer 5

Stem cell divides into one stem cell and one with ability to differentiate

Question 6

Independent choice

Answer 6

Stem cell division makes 2 identical cells but the outcome is stochastic and/or influenced by the environment

Question 7

Drawbacks of asymmetric division

Answer 7

Cannot explain how existing stem cells rapidly increase their numbers

Question 8

Flexibility of independent choice

Answer 8

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

Question 9

What happens if an adult organ needs to be renewed

Answer 9

Founder stem cells can divide, 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

Question 10

What determines founder cells during development

Answer 10

Short range signals

Question 11

Transit amplifying cells

Answer 11

Cells that divide frequently - Transit from a cell with stem cell characteristics to a differentiated cell
Programmed to divide a limited number of times

Question 12

Granular cells

Answer 12

Cell layer underneath prickle cells that form waterproof barrier between inner metabolically active strata and outer dead epidermis cells

Question 13

Outermost layer of skin

Answer 13

Squame- flattened dead cells densely packed with keratin

Question 14

Cell layer above basal cell layer

Answer 14

Prickle cells-several layers

Question 15

The only dividing cells in the epidermis are

Answer 15

Basal cell layer

Question 16

When basal cells move to layers above to renew, there is a change in

Answer 16

Change in gene expression at each step of differentiation

Question 17

Time from birth of basal cell to shedding is

Answer 17

One month

Question 18

What controls number of stem cells in basal layer

Answer 18

Contact with basal lamina

Maintenance of contact preserves stem cell potential, loss of contact triggers terminal differentiation

Question 19

Proliferative potential of stem cells is directly correlated to

Answer 19

Expression of B1 subunit of integrin (helps mediate adhesion to basal lamina)
Clusters of cells with high levels of integrin found near basal lamina

Question 20

Factors governing renewal of epidermis

Answer 20

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

Question 21

What is the most important signal for basal stem cells

Answer 21

Contact with basal lamina- mediated via integrin signaling

Loss of contact abolishes stem cell characteristics and promotes formation of cells that differentiate

Question 22

Overactivation of hedgehog pathway

Answer 22

Cells continue to divide after exit from basal layer

Question 23

Deficit of hedgehog signal

Answer 23

Loss of sebaceous glands

Question 24

Up regulation of Wnt signaling

Answer 24

Causes extra hair follicles to develop

Question 25

Loss of Wnt signaling

Answer 25

Leads to failure of hair follicle development

Question 26

Notch signaling

Answer 26

Restricts size of stem cell population

Question 27

Lateral inhibition causes

Answer 27

Neighbors of stem cells to become transit amplifying cells

Question 28

TGFb plays key role in

Answer 28

Repair of skin wounds, promoting formation of collagen rich scar tissue