Lecture #6-2 Flashcards
Relationship of resistance to radius?
to length?
to viscosity?
Res = 1/(r^4)
Proportional
Proportional
Increasing a vessel diameter by factor of four will alter resistance how?
1/256
If same pressure, flow increased by 256X
Why do arterioles have lower pressure?
Mnay small individual diameters add up to high resistance
Fluid resistances combine that same way as….
Electrical resistances
Eq. for velocity of fluid in a tube?
Flow rate/Area
Part of circulation with largest cross-sectional area?
Capillaries
Part of circulation with smallest cross-sectional area?
Aorta
What does viscosity measure?
Friction between layers as they slide past eachother at different velocities.
What is the unit of velocity?
Poise
What is relative viscosity?
Average Blood relative viscosity?
= Viscosity of Fluid / Viscosity of Water
= 3-4
Due to anomalous viscosity…
When might this matteR?
Blood viscosity increases if flow becomes slow
Shock
What is the Fahraeus-Lindquist effect?
Viscosity diminishes in smaller tubes
What is plasma skimming?
Vessels filling selectively from plasma layer
Reynold’s Number equation?
[(velocity)(diameter)(fluid density)]/viscosity
How should Reynold’s Number results be interpreted?
Turbulence tends to develop with a Reynold’s number over 2000
There is a ______ relationship between F and change in Pressure (in turbulent flow)
Linear
Name for the pressure at which the blood flow stops?
Critical Closing Pressure
Sypathetic stimulation _____ the critical closing pressure
Increases
in other words – at a higher pressure, blood flow stops
What is distensibility?
Percentage increase in vol caused by 1 mmHg pressure rise
What is the distensibility equ?
Dis = change in V / (change in P)(Vo)
What does compliance measure?
Increase in volume for a given increase in pressure.
Equation for compliance?
change in V / Change in P
OR
(distensibility)(Vo)
Give an example of delayed compliance/stress relaxation.
Initial Increase in volume –> distention+pressure rise
Smooth muscle fibers creep to longer lengths
Decreased pressure
What is reverse stress relaxation?
Volume of blood removed
Pressure Drop
Elastic Recoil returns pressure/Reduction in SmoMu. length
Veins are _____ compliant than arteries.
More
Two mechanisms of venous compensation during blood loss?
Elastic Recoil
Vasoconstriction via sympathetic stim
Increases in Central Venous pressure will also increase….
CO
according to Starling Law
Factors that may cause increased central venous pressure?
Increased Blood Volume
Vasoconstriction
Pumping of skeletal muscles
respiratory activity
Why are patients tilted down in brain surgery?
To keep air out of the saggital sinus
Wall tension equation?
Tension = Pr
Most important means of reducing pressure at the feet?
Venous Pump via skeletal muscle
Systole occurs between which two venous waves?
A and C
When is an a-wave absent? elevated?
Atrial Fib
Tricuspid Stenosis
What causes cannon a-waves?
atrial contraction against closed tricuspid
What does a large and early V-wave mean?
Tricuspid insufficiency
What does a slowed Y descent imply?
Narrowed AV
Venous Pressure curve change for mitral stenosis.
Elevated LAP
Slowed Y Descent in LAP curve
What is Kussmaul’s Sign?
JVP rises on inspiration
Caused by pericarditis, cardiomyopathy, and tamponade
Four types of capillary endothelium?
Continuous
Fenestrated
Discontinuous
Tight-Jxn
Where is continuous endothelium? Whats it for?
Skin, Muscle, Lungs
Clefts for transport of water and solutes
Where is fenestrated endothelium? Whats it for?
GI, Glands, Glomerulus
Heightened permeabitities
What is discontinuous endothelium?
Gaps of 1 micromaeter or more
Proteins pass through freely
Liver, Spleen, Marrow
What is tight junction endothelium?
Retina and CNS – Makes BBB
Vessel type with main control of peripheral resistance?
Arterioles
AV anastomoses play an important role in…
heat Exchange
T or F. Blood continuously flows through the capillaries.
F. It flows intermittently due to vasomotion.
What is vasomotion.
Intermitten contraction/relaxation of terminal arterioles and precap. sphincters.
Three ways through endothelial cell walls
Diffusion
Pinocytosis
Ultrafiltration
Who moves through endothelium by diffusion?
CO2, O
Who moves via pinocytosis?
Large, lipid-insoluble molecules
What two types of pressure play the biggest roles in ultrafiltration?
Colloid Osmotic and Hydrostatic
Name for forces involved in ultrafiltration.
Starling Forces
Why do we not usually care about the reflection coefficient?
Tells about degree of protein leakiness
Unless special pathology, its just 1
Difference between active and passive pumping of lymphatics?
Passive – External compression of lymphatics by muscles, arteries, or movement
Active – Smooth muscle contractions in the lymphatic vessels. Occurs when walls are distended.
What is edema?
Swelling of tissues caused by abnormal excess of fluids
Causes of edema?
Venous Pressure Increase
Lowered Plasma Oncotic Pressure
Raised Interstitial Oncotic Pressure
Blockage of Lymphatics
Causes of high venous pressure?
Heart Failure
Fluid Retention
Outflox Obs.
Immobilization
Four causes of Pulmonary Edema?
Imbalance of Starling Forces
Damage to Alveolar-Capillary Barrier
Lymphatic Obstruction
Idiopathic
What is cardiogenic pulmonary edema?
High Pulmonary Venous Pressure
Reduced Lymph Flow from lungs
Edema from increased transcapillary filtration and inadequate lymphatic drainage.
What is permeability pulmonary edema?
Endothelial cell injury causes leakage of fluid/protein ito interstitial space, causing osmotic changes.
