Specialized Tissues, Stem Cells and Tissue Renewal I Flashcards
What are the characteristics of stem cells?
not terminally differentiated can divide without limit ability to renew themselves when divide each new cell has ability to remain a stem cell or become differentiated into a different cell type undergo cell division
What is totipotency?
ability of a cell to give rise to all cells of an organism, including embryonic and extra embryonic tissue
A zygote is what type of cell?
totipotent cell
What is pluripotency?
ability of a cell to give rise to all cells of the embryo and subsequently adult tissues
Embryonic stem cells are what type of cell?
pluripotent cell
What is multi potency?
ability of a cell to give rise to different cell types of a give lineage
adult stem cells are what type of cells?
multipotent
A steady pool of stem cell population maintained by:
asymmetric division
independent choice
What is asymmetric division?
creates 2 cells, one with stem cell characteristics and another with the ability to differentiate
What is independent choice?
division makes 2 identical cells but the outcome is stochastic and/or influenced by environment
What is a drawback to asymmetric division?
cannot explain how existing stem cells rapidly increase their numbers
Why is the independent choice more flexible?
explains the sharp increase in stem cell numbers when needed to repair
If the adult organ needs to be renewed, founder stem cells can divide give rise to what?
one daughter cell that remains a stem cell and a set of cells that have a set number of transit amplifying divisions
Do transit amplifying stem cells divide frequently?
yes
Adult stem cells are ______ specific
tissue
Describe the epidermis
- forms the outer covering of skin
- creates a water barrier
- made of epithelial cells
- continously repaired and renewed
What is the dermis?
second layer, rich in collagen, provides toughness
What is the hypodermic?
fatty subcutaneous layer
the extracellular matrix of the skin is secreted by ______ that provide _____
fibroblasts, mechanical support
Epidermis is a stratified layer made of ______
keratinocytes
describe prickle cells
have numerous desmosomes that attach tufts of keratin filaments
granular cells are sealed together to form a ______ barrier
waterproof
What boundary does the granule cell layer form?
inner metabolically active strata and outer dead epidermis cells
What is the outermost layer the epidermis called?
squame
What is the squame?
flattened dead cells densely packed with keratin but with no organelles
proliferative potential of stem cells directly correlates with expression of what?
B1 subunit of integrin
What are the factors that govern renewal of epidermis?
- rate of stem cell division
- probability that one of the daughter cell will remain 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
_____ signaling mediates epidermis renewal
integrin
Over activation of hedgehog pathway makes what happen?
makes cells continue to divide even after exit from basal layer
What happens when there is a deficit of hedgehog signal?
loss of sebaceous glands
What happens when there is an up regulation of Wnt signaling?
extra hair follicles to develop and give rise to tumors
Loss of Wnt signaling leads to what?
failure of hair follicle development
What does notch signaling restrict?
size of stem cell population
What does lateral inhibition cause?
neighbors of stem cells to become transit amplifying cells
TGF beta plays a key role in what?
repair of skin wounds promoting formation of collagen rich scar tissue
