Vascular bio 2 Flashcards
what’s the arteriole’s counterpart?
venuole
what are the three types of capillaries? are there any subclasses?
- continuous
- fenestrated: subclass- with diaphragm and w/o
- sinusoidal
pericyte
contractile
mesenchymal cells
can differentiate into fibroblasts and SM cells
what is the structure of continuous capillaries?
- Have tight jxns between endothelial cells and linked with zona occludens
- lack pores between endothelial cells (continuous)
- have lots of pinocytotic vesicles (because completely closed so need a way to tx stuff)
- well developed basal lamina
where do we find continuous capillaries?
-brain, muscle, connective tissue, exocrine glands
what is the structure of fenestrated capillaries?
- have fenestrations in the walls of endothelial cells
- pores usually closed by thin diaphragm
- basal lamina is continuous
where are fenestrated capillaries normally located?
- Where there is rapid exchange
- kidneys (NONGLOMERULAR) , endocrine glands, intestines
where are fenestrated capillaries that lack a diaphragm over the pores?
the glomerular kidney
what is unique about the pinocytotic vesicles in continuous capillaries?
they can form a channel by which things can travel from lumen to outer layers of the blooc vessel
sinusoidal capillaries structure
- HUGE openings between endothelial cells
- discontinuous or absent basal lamina
- 30-40 micrometers (vs 5-10)
- ASSOCITATED WITH MACROPHAGES
where are sinusoidal capillaries usually found?
- in areas of rapid exchange and where cells can be exchanged
- red bone marrow (to allow synthesized cells to rapidly enter the blood stream especially w/o basal lamina blocking it), liver, spleen, adrenal cortex
what are the types of venules?
- pericytic venules (have pericytes around them and are the smaller version)
- Muscular venules- that have SM in them (larger)
what does the tunica media look like in veins? how about the adventitia?
internal/external membranes?
- media- thin
- adventitia- thick
- no internal and external elastic membranes
vasculogenesis
de novo vessel formation
angiogenesis
growth from existing extracellular derived channels
arteriogenesis
formation of arteries, arterioles and collateral vessel remodeling
neovascularization
OVERACARCHING term used to define arteriogenesis, angiogenesis and vasculogenesis
remodeling
- vascular response to alterations in the environment
what two mechanisms are used to develop blood vessels?
- from endothelial precursor cells
- from pre-existing vessels
what methods of neovascularization do tumors use?
BOTH
- forming from endothelial precursor cells
- from pre-existing vessels
where do endothelial precursor cells (EPCs) usually reside and describe what occurs
-they usually reside in the bone marrow and migrate to the area where the new blood vessel will be formed. mechanism unknown
what kind of vessels do EPCs replace?
lost endothelial cells
reendovascularization of vascular implants (stents)
neovascularization of ischemic organs, wounds, and tumors
what is the mechanism by which neovascularization occurs from pre-existing blood vessels?
1) vasodilate the vessel via NO
2) Increase vascular permeability by VEGF
3) Partially degrade basal lamina by metaloproteinases
4) disrupt intracellular proteinases by plasminogen activator
5) Ang-2 destabilizes the vessels
6) when everything is destabilized, the endothelial cells will proliferate and migrate and form a capillary tube
7) Stabilize: elaboration of the basal lamina by TGF-Beta and recruitment of the periendothelial cells and smooth muscle (mediated by ang-1, tie2, and PDGF- platelet derived growth factor)
Ang-1 vs ang-2
ang-1 stabilizes and ang-2 destabilizes
