Chapter 23 Liver/ Blood Vessels
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What is the entire endothelial system?
blood vessel lined by endothelial cells
Explain arteries and capillaries.
Capillaries are only basal lamina and endothelium
arteries: loose connective tissue, contracting smooth muscle, elastic lamina (expression and contraction of vessels), endothelial lining, and a basal lamina
What is passage of things in the blood vessels regulated by?
regulated by endothelial cells that line it
surround capillaries; some have contractile mechanisms; otherwise, they signal back and forth and communicate with growth of cells
A new blood capillary forms by the sprouting of an endothelial cell from the wall of an existing small vessel; an endothelial tip cell, with many filopodia, leads the advance of each capillary sprout.
The endothelial stalk cells trailing behind the tip cell become hollowed out to form a lumen.
A signal coming from adjacent tissue or growth of another tissue. The tissue is detected at the base of the basal lamina layer--> grows towards via a pseudopodial process--> continues to divide unti fusion with existing blood vessel
What does angiogenesis help do?
it helps regulate where blood vessels are and how/ where/ etc. they grow
What are the signals for growth of the blood vessel?
What activated the signal?
it is VEGF (vascular endothelial GF)
the TF responsible is hypoxia inducible factor
has two subunits--alpha nad beta
member of the HLH family
Beta subunit is always expressed; alpha subunit is also expressed under normal O2 levels
a prolylhydroxylase activates a degron on the alpha subunit, which leads to Ub attachment--> it is recycled by the proteasome to lead to an end of simple duplication
Expalain HIF and VEGF in the presence and absence of oxygen.
Low O2= build-up of succinate, inhibiting prolyl-hydroxylase; alpha subunit is no longer ubiquitylated and now persists--> binds to Beta subunit to form the complete HLH motif and binds to several genes encoding enzymes in the glycolytic pathway
Binds to promoter of VEGF to produce it
VEGF is released
Why can't simple duplication work for replacing tisues?
neuron regeneration (physical blockages)
cardiac and muscle cells (too complicated to re-enter cell cycle)
physical loss of skin cells
complete loss is too complicated and the connections made are too hard
unipotent vs. multipotent vs. totipotent
uni: one cell type
multipotent: can become multiple cell types
toti: can give rise to all of the cell types that make up the body
Explain how a stem cell divides.
as long as it is relatively undifferentiated, it can be certain distance down from the egg where you can become one, a few, or many types of cells.
One cell becomes terminally differentiated and another is self-renewed to regenerate the rest
relatively undifferentiated that can continue dividng indefinitely throwing off daughter cells; can undergo terminal differentiation into particular cell types
Difference between the epithelium and the layers between them?
extra cellular matrix
fuse together and die together; densely packed with keratin; ECM is absent
it is of a specific type of fibrous protein with 3 domains; a binding domain and an alpha helical section in the middle
two subunits dimerize and two more form a tetramer
cross-links are produced
overlapping, interconnected, and ropelike, making it durable
30 different keratin genes
As we move away from the basal layer, what happens?
Explain attachment of the basal layer and its layers up.
- attachment needed for division
- second layer up is the prickle layer, where desmosomes form= cell surface proteins that connect cells with each other
- As we move up, there are different keratin genes
What are the layers from the bottom up?
the layers from bottom to top are basal, prickle (keratin type), granular layers, keratinized squames, and flake offs
As you age what happens?
you age slower because stem cells
Keratin type 10 indicates
that it detaches basal layer and is now in the prickle layers
Explain the experiment ofstem cells in teh bulge of a hair follicle.
in this region, BrdU showed cells moving in both directions
- BrdU used to find stem cells with a short pulse of BrdU and a chase= not many stem cells labeled
- They had three times of pulse and chase combinations
- 1) original: quick pulse adn quick chase
- 2) long pulse, long chase
- 3) long pulse, quick chase
Explain stem cells in the epidermis
they are concentrated in one particular spot and divide as they migrate away
as son as contact is lost from basal lamina, differentiation occurs
Produces integrin (adhesive that binds to the ECM)
Beta1 subunit of integrin is expressed by true stem cells but not so much in transit amplifying cells; not at all in differentiated cells
There are two populations of cells that divide
- 1) true stem cells which divide infrequently
- 2) transit amplifying cells; have already taken step towards a differentiated state
What is the speed of TACs vs. stem cells?
TACs replicate more often adn have a built in timer; replicate a specific number of times before differentiation occurs
TACs are present to do what?
generate and renew a big adult structure, as well as created to maintain balance and tissue size
What are the two types of division?
env: two daughter cells identical; environment differs and causes either movement away towards differentiation or remaining in a comfortable environment
div: stem cell division/ one daughter cell receives certain factors, whereas the other daughter cell does not
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