19.1 Stem Cells and the Maintenance of Adult Tissues

Question 1

cells are still constantly proliferating in adult tissues → number of cells is maintained by the balance of (1) and (2)

Answer 1

1. cell proliferation
2. cell death

Question 2

epithelial stem cells are used in the form of () to treat burns, wounds, and ulcers

Answer 2

skin grafts

Question 3

the ff differentiated cells are able to proliferate as needed to repair tissue damage

Answer 3

1. fibroblasts
2. endothelial cells
3. epithelial cells

Question 4

fibroblasts proliferate quickly in response to () released at the site of a wound

Answer 4

platelet-derived growth factor (PDGF)

Question 5

PDGF works by () to stimulate fibroblast proliferation and fibroblast migration to the site of a wound

Answer 5

activating a tyrosine kinase (ERK pathway)

Question 6

endothelial cell proliferation allows for the formation of new blood vessels in response to (), which is produced by cells that lack oxygen

Answer 6

vascular endothelial growth factor (VEGF)

Question 7

vascular endothelial growth factor (VEGF) is produced by cells that ()

Answer 7

lack oxygen

Question 8

give an example of how epithelial cells of some internal organs maintain tissue

Answer 8

liver cells are normally arrested in G0, but loss of large numbers of liver cells triggers proliferation of remaining liver cells to replace lost tissue

Question 9

most adult animal cells are differentiated cells that no longer able to proliferate; lost or damaged cells are replaced by proliferation of cells derived from ()

Answer 9

self-renewing stem cells

Question 10

less differentiated, self-renewing cells present in most adult tissues

Answer 10

stem cells

Question 11

key property of stem cells:

Answer 11

retain the capacity to proliferate and replace differentiated cells throughout the lifetime of an animal

Question 12

stem cells divide to produce

Answer 12

1. one daughter cell that remains a stem cell (self-renewing)
2. one daughter cell that divides and differentiates (source of differentiated cells)

Question 13

the differentiated cells do not themselves proliferate (i.e. blood cells do not proliferate); rather, the proliferation of stem cells maintains ()

Answer 13

a number of cells that readily differentiate to replace lost differentiated cells

Question 14

roles of stem cells:

Answer 14

1. maintaining differentiated cell populations
2. self-renewal of tissue
3. repair of damaged tissue

Question 15

blood-forming stem cells; first stem cell to be identified

Answer 15

hematopoietic cells

Question 16

100 billion human blood cells are lost everyday → continually produced from stem cells in the ()

Answer 16

bone marrow

Question 17

summarize the experiment by McCulloch and Till that led to the identification of stem cells

Answer 17

cells derived from mouse bone marrow could proliferate and give rise to multiple differentiated blood cell types

Question 18

summarize the process of epithelial cell proliferation at the intestinal lining

Answer 18

1. epithelial cells lining the intestine have short life spans due to stress (they undergo programmed cell death)
2. new epithelial lining cells are derived from the continuous but slow division of stem cells at the bottom of intestinal crypts
3. new cells proliferate for 3-4 cell divisions and then differentiate

Question 19

stem cells are also responsible for the continuous renewal of ()

Answer 19

skin and hair

Question 20

multilayered epithelium that undergoes continual cell renewal

Answer 20

epidermis

Question 21

explain how stem cells are involved in self renewal of the epidermis

Answer 21

epidermal stem cells exist in one layer, and as epidermal cells are sloughed off, new cells proliferated from ESCs differentiate to replace lost cells

Question 22

stem cells responsible for hair production reside in a region called the ()

Answer 22

bulge

Question 23

stem cells in the bulge can also give rise to () in the event of skin injury

Answer 23

epidermal or sebaceous gland cells

Question 24

(1) and (2) can regenerate rapidly in response to injury or exercise; normally have little cell turnover

Answer 24

1. skeletal cells
2. satellite cells

Question 25

adult muscle stem cells

Answer 25

satellite cells

Question 26

why do stem cells generally undergo several divisions before differentiating in response to injury or other factors

Answer 26

transit-amplifying divisions allow the cells (that will differentiate) to reach the target area faster

Question 27

it appears that stem cells reside within distinct microenvironments called ()

Answer 27

niches

Question 28

niches provide the () that maintain stem cells throughout life and control the balance between their self-renewal and differentiation

Answer 28

environmental signals

Question 29

signalling by the () is a major role in controlling the proliferation of epithelial stem cells

Answer 29

Wnt pathway

Question 30

() secreted by adjacent epithelial cells and fibroblasts control proliferation of intestinal stem cells

Answer 30

Wnt polypeptides

Question 31

(1) aka (2) plays an important role in the treatment of a variety of cancers

Answer 31

1. bone marrow transplantation
2. hematopoietic stem cell transplantation

Question 32

what is the main problem of chemotherapy

Answer 32

• they nonselectively target rapidly dividing cells and damage DNA/inhibit DNA replication
• many normal cells (e.g. hematopoietic cells) also rapidly divide, thus they can also be targeted by chemotherapeutic drugs/methods

Question 33

summarize how bone marrow transplants are useful in chemotherapy

Answer 33

bone marrow transplants bypasses this toxicity to hematopoietic system and thus allows for the use of higher doses of chemotherapy drugs → cancer is treated more effectively

Question 34

after administering high-dose chemotherapy, hematopoietic stem cell transplants aid in the ()

Answer 34

restoration of the hematopoietic system