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| Major Blood Vessels and Direction Flow |
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Definition
Large artery (elastic artery)--> medium artery (muscular artery)--> small artery and arteriole--> capillary--> small vein or venule (postcapillary & muscular) medium and Large vein
Exceptions: 1. systemic portal systems in which a vein may be found between 2 capillary networks and 2. arteriovenous shunts bypass caps(from artery to vein) |
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| composed of single layer of endothelial cells, the basal lamina, sub-endothelial layer-loose Ct (in arteries: also a layer of fenestrated elastin (internal elastic membrane/IEM) |
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| concentric layers of smooth muscle, sheets of fenestrated elastin, collagen fibers. Extends from IEM to external elastic membrane: elastin layer separating media and adventitia |
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| longitudinally arranged connective tissue (large vessels have vasa vasorum, & autonomic neural tissue/nervi vascularis) |
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conductin arteries- they conduct blood from the heart to the medium-sized so-called distributing arteries
also fenestrated tunical media
receive blood from heart under high pressure
elastic walls distend ruding systole and recoil during diastole |
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Distributing arteries- allow selective distribution of blood to diff. organs in response to functional needs.
prominent internal elastic membrane, thicck tunica adventitia and recognizable EEM |
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| resistance vessels (major regulators of systemic blood pressure) |
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thin tubes consisting only of endothelial cells and their basal samina (about 4-10 microm), one RBC at a time
3 types
Continuous (muscle, lungsm CNS, fenestrated (endocrine glands and GI) pores
discontinuous/sinusoidal (liver, spleen, bone marrow) gaps and incoplete basal lamina |
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| the basal lamina is discontinuous, in th spleen blood cells can pass readily through the walls of the splenic sinuses |
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| fenestrations on the endothelial cells, the basal lamina is continuous in tissues with substantial fluid transport (choroid plexus, intestinal vilil), also present in the glomerular capillaries of the kidney supported by significantly thicker basal lamina |
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endothelial cells and basal lamina have a complete cytoplsm, found in muscle, brain, thymus, bone, lung \
caveolae and vesicles transport substances through the cytoplasm in a bidirectional pathway (transcytosis) |
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postcapillary venule: resembles continuous capillary but with wider lumen: site of diapedesis of WBCs
Veins- have three tunics, T. media is thinner than in arteries, thinner walls and larger lumens and veins have valves to prevent reflux of blood (low pressure system) |
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capillaries form networks in tissue spaces and convey tissue fluids and wbc to larger lymph vessels
vessels unite to form 2 channels that empty into the veins at the base of the neck
capillaries lack continuous basal lamina and thus are highly permeablle ( to remove protein-rich fluid from intercellular spaces) |
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| have an irregular outline, a spaced endothelial cell lining lacking tight junctions, and no RBCs in the lumen |
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downstream of endothelial injury, "hardening" of the arteries due to fibrofatty intimal plaques, blood vessel lumens decrease, and are susceptible to occlusioon = ischemia (restriction of blood supply)
Risk factors: high LDL levels, DM, Hpertension, smoking |
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| lesion due to the deposition of fatty material in the wall of the vessel; usually in large (elastic) arteries |
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damage to the endothelium of an artery- caused by hypercholesterolemia and increase of LDL in TI
lipids are take up by macrophages
macrophages and fibroblast release the lipids in the subendothelial space and cytokines stimulate proudction of collagen by SMCs
the ulceration fo the atheroma provides a surface for thrombosis (clot) |
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vasculogenesis (creation of a new vascular network)
angiogenesis (sprouting form existing vascular network) |
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degradation of the basal lamina to enable formation of a capillary sprout
migration and proliferation of endothelial cells, stimulated by angiogenic factors (VEGF, Ang1`)
maturation of endothelial cells into an endothelial capillary tube
assembly of a basal lamina and |
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Definition
Angioblasts proliferate and form endothelial capillary tubes (VEGF-R2-VEGF (ligand) interactions)from mesenchymal cell
capillary endothelial tube formation
Tie2 receptor (a receptor tyrosine kinase)interacts with angiopoitins (Ang1 and 2) to recruit periendothelial cells to sMCs in large vessles to organize mature blood vessels
ANg2 interacts with Tie2 to induce loss of contact of endothelium cells with ECM
regulting in either the absence of growth or death of endothelialc ells. |
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tumors have the ability to recruit blood vessels, which provide nutrients required for tumor growth
two antianglogenic pepetides anglstatin and endostatin can stop or slow cancer growth in mice by preventing the dev. of new blood vessels needed nourish growing tumors |
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