A&P Chapter 15

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A&P Chapter 15
2014-07-01 17:27:32
Vascular Distensibility, Arterial & Venous Systems
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  1. Veins are ____ times more distensible than arteries
  2. What is vascular tone?
    the normal semi-contracted state blood vessels exhibit
  3. How does the distensibility of a tube affect flow?
    increased distensibility allows more flow for a given perfusion pressure
  4. Does a small distensible blood vessel exposed to high pressures exhibit more or less resistance than the same vessel exposed to lower pressure?
    less resistance 

    As the pressure increases the radius of the vessel increases which decreases resistance and increases flow
  5. What is tension?
    the internal force generated by a structure
  6. What is the formula for LaPlace's Law for for cylinders?
    T = P x R
  7. As a structure expands, the tension (force in the wall of the structure) increases or decreases?
  8. What does Laplace's Law mean for the thickness of walls of small and large vessels?
    In order to withstand the same pressure, a vessel with a large diameter must have thicker walls
  9. How does LaPlace's Law relate to the Frank-Starling law?
    Greater the filling pressure = greater the tension


    LaPlace = increased tension with increased filling

    Frank Starling = increased tension = increased stroke volume
  10. How do you calculate vascular distensibililty?
    (increase in volume)/(increase in pressure x original volume)

    So if volume increases by 1 ml and pressure increases by 1 mmHg and original volume was 10 ml, the distensibility is 10%
  11. How does the same volume fit in the systemic circulation as the pulmonary circulation?
    Pulmonary vasculature is 6x more distensible than systemic vasculature
  12. What is vascular capacitance or compliance? What two things contribute to compliance?
    the total quantity of blood that can be stored in a given portion of the circulation for each mmHg of pressure

    Distensibility and volume
  13. Are the veins more or less compliant than arteries?
    24x more compliant
  14. What happens to the compliance of our vessels as we age?
    They become stiffer, less distensible, and less compliant so to hold the same volume, the pressure will increase much more
  15. What is delayed compliance or "Stress-relaxation?"
    • a vessel has an initial increase in pressure when exposed to an increase in volume but the smooth muscle eventually stretches and the pressure returns to baseline.
    • The reverse is true for a decreased pressure.
  16. What does the dicrotic notch (incisura) represent?
    produced when the aortic valve closes which causes a brief period of retrograde flow from aorta back toward the valve that briefly causes aortic pressure to be less than systolic pressure
  17. What is the formula for MAP?
    (systolic x diastolic x diastolic) / 3
  18. What 2 factors affect pulse pressure?
    • 1: stroke volume output
    • 2: compliance of arterial tree
  19. What 2 things contribute to the decreased presence of pulse waves in the smaller arteries?
    • 1: increased resistance
    • 2: increased compliance
  20. Why is the pulse pressure wider in the large arteries than in the aorta?
    aorta is more compliant
  21. What is the driving force for blood flow in arteries?
    mean arterial pressure
  22. How does arteriosclerosis change your pulse pressure?
    increases (d/t decreased compliance)
  23. How does aortic stenosis change your pulse pressure?
    decreases (d/t decreased outflow)
  24. How does a patent ductus arteriosis change our pulse pressure?
    increases - increased systolic, slightly decreased diastolic

    large portion of blood pumped from LV flows back into pulmonary artery
  25. How does aortic regurgitation change your pulse pressure?
    increases - diastolic may approach zero, systolic elevated

    blood pumped from LV flows immediately back into LV.

    No dicrotic notch because no aortic valve closure.
  26. What are 5 things that narrow pulse pressure?
    • - tachycardia
    • - severe aortic stenosis
    • - constrictive pericarditis¬†
    • - pericardial effusion
    • - ascites
  27. What is a normal MAP?
    70 - 110
  28. The spleen is a reservoir for what 2 things?
    blood and RBC's
  29. How does an increased right atrial pressure affect venous pressure?
    it causes blood to back up into the venous system which increases venous pressure
  30. What is a normal CVP? What is the low limit?
    0. Lower limit is -3 to -5
  31. What 4 things increase RAP?
    • - increased blood volume
    • - increased venous tone
    • - dilation of arterioles¬†
    • - decreased cardiac function
  32. What is the pressure in legs when standing?
    90 mmHg
  33. If abdominal pressure increases, what has to happen to the venous pressure in the legs? why?
    it also has to increase to overcome abdominal pressure and flow back to heart
  34. Why is there a risk for venous air embolism during a craniotomy/opening of sagittal sinus?
    veins inside the skull are negative pressure because they are in noncollapsible chamber