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21 Cards in this Set
- Front
- Back
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Hemodynamics
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-refers to the principles that govern blood flow in the cardiovascular system
25% to kidneys 25% to GI 25% to skeletal 15% cerebral 5% coronary 5% skin -this can be altered by demand by autoregulate -brain, kidneys, & coronary (dilate/constrict) -others don't have this ability |
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Arteries
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-deliver O2 blood in systemic system
-thick walled -significant elastic recoil (esp aorta) -under highest pressure -carry blood away from heart -aorta ~2.5cm |
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Arterioles
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-extensive development of smooth muscle
-site of greatest resistance & largest drop pressure -um in size -most difficult for blood to flow thru |
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Artery Wall Anatomy
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Tunica intima (inner coat)
-endothelial cells (innermost) -CT -internal elastic membrane Tunica media -smooth muscle cell (vascular) Tunica externa (adventitia) -elastic tissue -collagen (strong protein) *don't exchange any nutrients w/ tissue bc of thickness of wall |
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Arteriolar Resistance
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Affected by (radius wise):
-SNS activity -Circulating hormones (angiotenssin II vasopressin) -local vasoactive substances -other ie: temperature |
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Capillaries
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-exchange vessels: form leading to fxn
-1 layer= tunica intima -endothelial cells spaced further apart (pores) -minimal CT & elastic tissue -don't have as thick basement mem -no smooth muscle (no dilate/constrict) -can increase BF to arterioles = increase BF to capillary & stretch out -thus perfusion of cap determined by arterioles -greatest cross-sectional area (4500cm2) -found w/in every organ |
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Venules & Veins
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-venules smaller (um)
-veins larger can see w/ naked eye (cm) -largest = vena cavae -thin walled (same 3 tunics) -less elastic tissue, less muscle tissue (thinner tunica media) -larger capacitance (ability to hold more blood at given time than artery) -venous valves w/in endothelium (not all veins contain) prevent backflow of blood (overcome gravity) |
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Vaso- constriction/dilation
Veno- constriction/dilation |
arteries
veins |
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Arteries of Systemic Circulation
Veins (similar) |
-aorta: brachiocephalic (R subclavian & R common carotid), L common carotid, L subclavian
-coronary arteries -arteries to head/neck -arteries of upper & lower limbs -thoracic aorta & branches -abdominal aorta & its branches -arteries of pelvis |
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Ohm's Law
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flow (Q) = P/R
-Q: quantity of BF thru a vessel, organ or entire circulation in given period of time -BF driven by pressure differences (gradients) in same sense that simple diffusion of a chemical substance driven by gradients |
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Blood Pressure
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-force w/ which blood is pushed against the walls of BV
-BP progressively falls thru circulation: further away from pressure creator the heart & different distribution of pressure thru body (3 paths from aorta) |
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Systolic Pressure
Diastolic Pressure |
highest amount of pressure reached during ventricular ejection of blood
minimum amount of pressure just before ventricular ejection begins |
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Recoil
Wind Kessel effect |
-arterial wall potential energy released, propels the blood distally (diastolic runoff)
pressure-storing property of aorta -alteration of systolic & diastolic propulsion provides more continous rather than pulsatile flow to peripheral tissues |
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Korotkoff Sounds
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-sounds heard when measuring BP
-creating hyperemia, create situation of turbulence -arm cuff occlude blood flow for ~15sec, let cuff go creates turbulence -1st sounds = systolic pressure ~120 mmHg -2nd sound = diastolic pressure ~80 mmHg |
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Mean Arterial Pressure (MAP)
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-pressure that propels blood to tissues (avg pressure in cardiac cycle)
-pressure lies bw systolic & diastolic ~93-94 avg MAP = 2/3 DP + 1/3 SP MAP = DP + 1/3 PP |
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Resistance (R)
Total Peripheral Resistance (TPR) or Systemic Vascular Resistance (SVR) 3 Imp sources of resistance w/in single vessel: |
-the opposition to blood flow
-sum of all resistance in the vasculature -essentially most of it comes from the arterioles 1. blood viscosity 2. vessel length (doesn't change as drastic as other 2) 3. vessel diameter or radius |
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Poiseuille's Law
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relationship bw resistance, viscosity, vessel length, & vessel radius
R = 8VL/(pi x r^4) |
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Blood Viscosity
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-hematocrit: % of cells in blood
-too many RBC = increase in viscosity -plasma: water portion of blood -lack water = viscous -RBC aggregate into stacks of "rouleaux" at lower flow velocities -rouleaux: exaggerated in low flow states such as burn of shock, pronounced cell clumping or "sludge" in microcirculation w/ severe hindrance to flow & tissue ischemia |
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In low hematrocrit such as anemia:
What happens to viscosity? What happens to vascular resistance? In high hematrocrit such as polycythemia & leukemia: |
V = down
R = down V = up R = up |
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Blood Vessel Radius
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-2-fold increase in vessel radius augments flow by 16-fold
-4-fold incrase in vessel radius augments flow by 256-fold -drugs that dilate vessels thus have powerful effect on blood flow |
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Arteries vs. Veins
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arteries:
vasoconstriction: resistance increases more than pressure -> BF decreases Veins: -venoconstriction: pressure increases more than resistance -> BF increases -> venous return increases |
