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37 Cards in this Set
- Front
- Back
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What is the objective of the vascular system?
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To maintain the quality and volume (10-15 L) of extracellular fluid
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Where does oxygen and nutrient replenishment occur?
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In each tissue's microvascular/capillary bed
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What is the microvascular/capillary bed comprised of?
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small arteries & arterioles
capillaries post-capillary venules venules |
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What is the maximum distance cells must be from capillaries?
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200 μm
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What are the three things that cover the blood vessels?
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1) tunica adventitia
2) tunica media 3) tunica intima |
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Describe the tunica adventitia.
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- outermost covering of vascular structures/blood vessels
- mostly connective tissue - vasa vasorum = blood vessels have their own vascular system - nervi vascularis = blood vessel's nerve supply |
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Describe the tunica media.
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- middle covering of vascular system structures/blood vessels
- most variable layer - smooth muscle cells + connective tissue |
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Describe the tunica intima.
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- innermost covering of vascular system structures/blood vessels
- endothelium with basal lamina + connective tissue - endothelium comprised of tight junctions to keep blood in vessel - at capillary portion of vessel, the structure becomes "leaky" |
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What are the three things that cover the heart (similar to blood vessel tunic coverings)?
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1) epicardium
2) myocardium 3) endocardium |
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Describe the epicardium.
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- similar to tunica adventitia
- simple squamous mesothelium with connective tissue - blood vessels and nerves (vasa vasorum/nervi vascularis) enter heart here |
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Describe the myocardium.
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- similar to tunica media
- cardiac myocytes - cardiac fibroblasts - coronary arteries & veins |
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Describe the endocardium.
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- similar to tunica intima
- simple squamous endothelium/basal lamina + connective tissue - Purkinje cells (cardiac conduction system) located in sub-endocardium |
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What are the differences between arteries and veins?
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Arteries:
- thick, highly developed wall, small lumen - tunica media = highly developed, lots of elastin + smooth muscle cells Veins: - thin, under-developed wall, large lumen - nondescript tunica media - tunica adventitia = thickest covering |
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Describe large/elastic arteries.
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- thick wall, small lumen (relative to large veins)
- tunica media = many layers of smooth muscle cells + lamellae of elastin - tunica intima = tight junctions, pinocytotic vesicles (nutrients from lumen → tissue; Factor VIII secretions (blood coagulation)) - maintain blood pressure during diastole - aneurysms = dangerous outpocketing of tunica media |
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Describe large veins.
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- thick tunica adventitia
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Describe medium/muscular arteries.
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- tunica adventitia = prominent external elastic lamina
- tunica media = prominent layers of 40 smooth muscle cells ↳ possible problems: atherosclerotic plaques ↳ 1) macrophages migrate to damaged sites in endothelium → macrophages ingest LDL & cholesterol ↳ 2) smooth muscle cells migrate to tunica intima, proliferate, take up LDL ↳ macrophages + smooth muscle cells = foam cells ↳ foam cells → form plaques → stroke/heart attack |
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Describe medium/small veins.
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- have valves (esp. limbs)
↳ valves = fold of tunica intima, project into lumen, direct blood flow to heart |
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What are varicosities?
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Stretching of medium/small veins.
Exacerbated by sedentary lifestyles (leg mm. contractions normally send blood back to heart) |
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What is phlebitis?
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Inflammation of a vein (usually in leg)
May lead to thrombosis (blood clot) |
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Describe small arteries and arterioles.
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- lumen <50μm
- tunica media: ↳ small arteries = 8 layers of smooth muscle cells ↳ arterioles = 2 layers of smooth muscle cells - smooth muscle cells regulate blood flow to capillary bed Problems: - smooth muscle cells uptake lipids → lumen narrowing → hypertension |
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Describe venules.
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- lumen ~50μm
- on venous side of capillary bed, post-capillary venules encountered first - post-capillary venules = site where leukocytes enter tissue via diapedesis (passage of blood cells through capillary walls into the tissues ) |
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Describe capillaries.
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- no tunica adventitia or media
- 1 RBC at a time - single layer of endothelial cells + basal lamina ↳ exhibit biochemical differences from tissue to tissue ↳ express specific cell membrane receptors (eg, vascular endothelial growth factor receptor (VEGFR)) |
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What are the three types of capillaries?
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Type I: continuous
Type II: fenestrated Type III: sinusoidal (discontinuous) |
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Describe Type I (continuous) capillaries.
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- in heart, skeletal mm, CNS, lungs
- have tight junctions - have pinocytotic vesicles (not in CNS) → transport things from blood vessel lumen to adjacent connective tissue (direct, through cell) |
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Describe Type II (fenestrated) capillaries.
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- in endocrine organs, GI tract, kidney
- ~100nm diameter "windows" - allow passage of 10+ kDa molecules |
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Describe Type III (discontinuous) capillaries.
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- in bone marrow, liver, spleen
- endothelial lining (incl. basal lamina) NOT continuous - filter out entire RBCs |
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What is the main function of capillary endothelial cells?
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To exchange gases and nutrients
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How are <10kDa molecules transported through capillaries?
How are 10+ kDa molecules transported through capillaries? |
<10kDa:
- pass btn adjacent endothelial cells 10+ kDa: - must be transported directly through cell via pinocytotic vesicles & fenestrae |
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What do endothelial cells secrete?
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1) vasoactive factors
- endothelin: potent vasoconstrictcor - nitric oxide: vasorelaxant 2) growth factors/cytokines - fibroblast growth factors (FGFs) - platelet-derived growth factor (PDGF) - interleukins |
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What are lymphatics?
Where are they found? What do they do? What is lymphatic fluid comprised of? How is lymphatic fluid circulated? |
- very, very leaky vessels
- present in all tissues (except bone marrow & CNS) - provide one-way drainage from extracellular spaces → veins/venules - fluid composed of WBCs & lipids - fluid circulates via surround skel. mm. contractions |
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What is the difference between angiogenesis and vasculogenesis?
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- angiogenesis: blood vessel regeneration in adults
- vasculogenesis: embryonic blood vessel development |
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In angiogenesis, what are the ligands and receptors present?
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1) vascular endothelium growth factor (VEGF) & VEGFR
2) fibroblast growth factor (FGF) & FGFR 3) angiopoietin & Tie-2-R |
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What inhibits blood vessel formation?
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- angiostatin (derived from plasminogen)
- endostatin (derived from collagen XVIII) |
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What is pro-angiogenic therapy?
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- the ability to induce new vascular supply
- will help manage diseases such as ischemic heart disease and diabetes - uses FGF/VEGF to re-vascularize the heart |
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What is anti-angiogenic therapy?
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- may provide a therapeutic intervention to starve tumors of vascular supply
- endostatin: dramatic decrease in tumor volume shown in rats |
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What does Avastin do?
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- aka Bevacizumab
- monoclonal antibody that binds and inhibits VEGF - treats colo-rectal, breast and non-small cell lung tumors that have metasticized - current studies include: ↳ Avastin + synthetic anti-angiogenics (eg thalidomide) → seems to inhibit receptor production |
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What is Lucentis? What does it do?
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- Lucentis is a smaller form of Avastin (monoclonal antibody that binds and inhibits VEGF)
- used to knock-down blood vessels in treatment of macular degeneration |
