3.9 specialized tissues, stem cells Flashcards
What are stem cells?
unspecialized cells
why are stem cells important?
potential to develop into many dif cell types in the body
Stem cells can also serve as what to many tissues?
internal repair system.
What are 5 characteristics of stem cells?
can divide without limit. Can renew themselves. Not terminally differentiated. Can remain a stem cell or become differentiated. Undergo slow division
What is totipotency?
ability of a cell to give rise to all cells of an organism. Embryonic and extra embryonic tissues
What is an example of totiplotency?
zygote
What is pluripotency?
ability of a cell to give rise to all cells of the embryo and adult tissues
What is an ex of pluripotency?
embryonic stem cells
What is multipotency?
ability of a cell to give rise to different cell types of a given lineage
What is an ex of multipotency?
adult stem cells
What two ways are stem cells maintained?
asymmetric division and independent choice
What is asymmetric division?
creates 2 cells, one with stem cell characteristics and another with ability to differentiate.
What is independent choice?
division makes 2 identical cells but the outcome is stochastic or influenced by environment.
Which of the two (asymmetric or independent choice) is a better option?
independent choice
Differentiation of stem cells depends on what two types of signals?
internal and external signals
How are internal signals controlled by?
cells genes
How are the external signals controlled by?
cells micro environment.
Each organ/tissue has a fixed number what?
founder cell populations and fixed number of divisions
How are founder stem cells controlled?
by short range signals.
Pertaining to founder stem cells, if the adult organ needs to be renewed, founder stem cells can what?
can divide, having one daughter cell that remains a stem cell and a set of cells that have a set number of transit amplifying divisions.
What are transit amplifying cells?
cells that divide frequently and are mixed with stem cells
Transit amplifying cells are programmed to divide for how many times?
limited number of times
Adult stem cells are specific to what?
tissue
What is the architecture of the skin? 3 layers
Epidermis, Dermis and hypodermis
What does the epidermis do?
forms the outer covering of skin, creates a water barrier. continuously repaired and renewed.
What is the Dermis?
second layer of skin, rich in collagen, provides toughness
What is the hypodermis?
fatty layer
The epidermis is stratified layer made of what?
keratinocytes
the basal cell layer is attached to what?
basal lamina
prickle cells have what?
numerous desmosomes that attach tufts of keratin filaments
Granular cells form what type of barrier?
water proof
What is the squame?
outermost layer of the epidermis with flattened dead cells densely packed with keratin but no organelles.
Name the multilayered structure of the epidermis from outest layer to most inner.
Squame, Granular, Prickle, Basal lamina.
How does the epidermis renew?
with basal cells that move through the prickle then the granule cell layer.
Where do stem cells come from for the renewal of the epidermis?
basal layer
how are epidermal stem cells regulated?
By contact with basal lamina
How does contact with basal lamina control the number of stem cells in the epidermis?
Maintenance of contact preserves stem cell potential, loss of contact triggers terminal differentiation.
Proliferate potential of stem cells directly correlates with expression of what?
Beta 1 subunit of integrin
Intregrin signaling pertaining to epidermis stem cell renewal helps to control what?
size of stem cell population
What factors 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.
Where does hair grow upward from?
Dermal papilla
Sebaceous glands secret oily liquid called
sebum
Overactivation of hedgehog pathway makes cells do what?
cells to continue to divide even after exit from basal layer
What happens with a deficit of hedgehog signal?
loss of sebaceous glands
What causes extra hair follicles to develop?
up regulation of Wnt signaling
What signaling restricts size of stem cell population?
notch signaling.
What plays a key role in repiar of skin wounds?
TGFb