Vascular Biology II Flashcards
What type of junctions are found in continuous capillaries?
Tight junctions between endothelial cells. One cells folds over the other cell “marginal folds”
Do endothelial cells have pores of fenestrae?
NO
endothelial cells lack pores or fenestrae
How is information transferred in endothelial cells within continuous capillaries?
numerous pinocytotic vessicles
Where are continuous capillaries located? (4)
1) Brain
2) Muscle
3) Connective Tissue
4) Exocrine Glands
Where are fenestrated capillaries located?
Where rapid exchange of substances between the blood and tissue occurs
1) Kidney, nonglomerular
2) Endocrine glands
3) Intestines
4) Kidney [glomerulus- diaphrafms absent]
Describe the fenestrae (pores) present in the endothelial walls of fenestrated capillaries?
Pores are usually closed by a thin diaphragm
the basal lamina is continuous
How does the diameter of fenestrated capillaries compare to continuous capillaries?
They have the same diameter (5-10 micrometers)
Which type of capillary has a large opening between the endothelial cells?
Sinusoidal
Describe the basal lamina of the three different types of capillaries.
Continuous: well-developed
Fenestrated: continuous
Sinusoidal: DISCONTINUOUS OR ABSENT
What capillary type is associated with macrophages?
sinusoidal
Which type of capillary has the largest diameter?
sinusoidal (30-40 micrometers)
Where are sinusoidal capillaries located?
In areas of rapid exchange and where cells can be exchanged
1) Red bone marrow
2) Liver
3) Spleen
4) Adrenal cortex
What are the smallest types of veins?
Pericytic and muscular venules
Pericytic are smaller of the two
Veins have valves which can be used to indicate blood flow direction.
Look at the picture and know this.
What is the key identifier of large veins?
Longitudinal bundles of smooth muscle in the adventitia
*longitudinal arrangement allows contraction that pushes the blood back to the heart
Define vasculogenesis.
De novo vessel formation
Define angiogenesis.
Growth from existing EC-derived channels.
Define arteriogenesis.
Formation of arteries, arterioles, and collateral vessel remodeling
Define neovascularization.
Overarching term to include vasculogenesis, angiogenesis, and arteriogenesis.
Define remodeling.
Vascular response to alterations in the environment.
What are the two mechanisms of blood vessel formation in the adult?
1) From endothelial percursor cells (EPCs)
2) From pre-existing vessels
Which blood vessel formation method do tumors use?
BOTH
tumor angiogenesis employs both mechanism
What are EPCs?
angioblast-like cells that reside in the red bone marrow of adults and non-bone marrow niches
Describe EPC blood vessel formation. (What 3 things can they do?)
EPCs mobilize from niche and migrate to blood vessel formation site where they
1) Replace lost endothelial cells
2) Re-endothelize vascular implants
3) Neovascularize ischemic organs, wounds, or tumors
List the 6 basic steps to blood vessel formation from pre-existing blood vessels.
1) Vasodilation (NO) and increased permeability (VEGF)
2) Degradation of BL mediated by MMPs and disruption of intracellular junctions mediated by plasminogen activator.
3) ANG-2 destabilizes vessels.
4) Migration and proliferation of endothelial cells mediated by VEGF and FGF.
5) Formation of endothelial capillary tube.
6) Elaboration of BL by TGF-B and recruitment of periendothelial cells (pericytes of SMCs) mediated by ANG-1-TIE-2 and PGDF.
What is the difference between ANG 2 and ANG 1?
ANG-2 destabilizes
ANG-1-TIE-2 stabilizes
What is the function of NO?
Vasodilation of pre-existing blood vessel
What is the function of VEGF?
1) increased vascular permeability of pre-existing vessel
2) induces migration and proliferation of endothelial cells
What is the purpose of MMPs?
Proteolytic degradation of the basal lamina of the parent vessel by metalloproteinases
What mediates the loss of cell-to-cell contact?
Plasminogen activator
What three factors mediate the endothelial cell migration and proliferation?
VEGF
angiopoietin 2
Fibroblasst growth factor 2
What periendothelial cells are recruited in blood vessel formation?
1) Pericytes for capillaries
2) Pericytic venules and smooth muscle cells for larger vessels
What factor is responsible for elaboration of basal lamina elements?
TGF-beta
transforming growth factor
What mediates the recruitment of periendothelial cells?
Interaction of Ang 1 with the Tie2 receptor on endothelial cells
What is the function of PDGR (platelet derived growth factor)?
Induces recruitment of smooth muscle cells
How is Ang 2 involved in the remodeling process?
by blocking the stabilizing function of Ang 1
What are 6 potential clinical benefits of proangiogenesis ?
MI (myocardial ischemia) Peripheral ischemia Cerebral ischemia Wound healing and fracture repair Reconstructive surgery Transplantation of islets of Langerhans
What are 6 potential clinical benefits of antiangiogenesis?
Tumor growth and metastases Ocular neovascularization Hemangiomas Rheumatoid arthritis Atherosclerotic plaque neovascularization Birth control
How can endothelial cells of tumor vessels be specifically targeted?
They express a prtn called tumor endothelial marker 8 (TEM8)
Since this prtn is preferentially expressed in tumor vessels, the marker ca be used to specifically deliver drug molecules to tumor vessels
Why can the great saphenous vein be used in coronary bypass surgery?
Atypical vein: 2 or 3 layers of smooth muscle in its media
Wall remodeling will occur after the bypass to make it even more suitable!
