Lecture 9+10+DLA Flashcards
What is Darcy’s law?
Flow = Pressure / Resistance
What are the three kinds of pressure in the CV system?
- Driving pressure - pressure along the length of a vessel
- transmural pressure- influences the diameter of the blood vessel
- hydrostatic pressure - pressure created by the weight of blood (important in capillaries)
What is the equation for driving pressure?
DP = MAP - RAP
How to determine Cardiac output
CO = MAP- CVP/ TPR
CVP is usually 0, unless in heart failure
What is Poiseuille’s Law?
Flow = pressure X pi x R(4) / 8 x viscosity x length
Resistance = 8 x viscosity x length / pi x radius (4)
resistance is most sensitive to changes in radius
What blood vessel has the greatest resistance?
Arterioles
capillaries have the greatest when they are in series not in parallel
one capillary not a capillary bed
What happens during vasodilation in the arterioles?
short-term = increased pressure at capillaries, increased edema
septic shock or anaphylaxis occurs during massive vasodilation. (hypotension, reduced tissue perfusion, changes in HR)
exercise- massive reduction in resistance, but blood flows to other areas to maintain MAP
Graves disease
immune disorder that leads to hyperthyroidism, thus arteriolar vasodilation
reduced arteriolar resistance leads to reduced dampening of pulsatile arterial pressure in capillaries
pulsatile flow can be seen in the capillaries in fingernail beds
vasoconstriction in the arterioles?
short-term = reduced pressure at capillaries
pre-eclampsia is the result of major vasoconstriction, thus reduced pressure in capillaries and reduced tissue perfusion.
capacitance and resistance vessels?
capacitance = venules and veins (affect preload)
resistance = arterioles (affect afterload)
regulating flow to the organs?
blood distribution is in parallel and the pressure between the aorta and the arteries are similar
what affects resistance?
sympathetic’s = vasoconstriction (endothelin and serotonin)
vasodilators = nitric oxide, histamine adenosine
small arteriole radius leads to a larger resistance
velocity equation?
velocity = flow / cross sectional area
capillaries have the largest cross sectional area and have the slowest velocity.
Reynold’s equation?
factors that impact turbulence and what leads to that?
factors that increase turbulence:
high flow velocity
large vessel diameter
high blood density
factors that decrease turbulence:
increase viscosity
Reynold’s number determines whether flow will be laminar or turbulent
Re = velocity x diameter x pressure / viscosity
turbulence usually occurs due to defective valves and narrowed blood vessels
La Place’s law?
clinical example?
Pressure = 2(tension) / radius
aneurysm:
a point can be reached where the wall cannot generate any more wall tension
compliance of arteries and veins?
veins are compliant - for a small change of pressure they increase their volume greatly
arteries are not compliant - large pressure does not change their volume to much
venoconstriction and venodilation
increased sympathetic = venoconstriction
gets blood out of the veins and shifts it towards the heart
decreased sympathetic = venodilation
allows for more venous pooling and decreases venous return
pulse pressure equation?
PP = SBP - DBP
How to calculate mean arterial pressure?
MAP = P (diastolic) + 1/3 x P(sys) - P (dias)
Fick principle?
Rate of O2 removal = O2 pulmonary flow in artery - O2 pulmonary flow out in vein
physical factors of microcirculation
- hydrostatic pressure - capillary pressures drive fluid out of capillaries and into interstitial space
- oncotic pressure - keep fluids in capillaries and drive reabsorption
- capillary walls - more permeable
- lymphatic drainage - remove excess interstitial fluid
starling-landis equation
net filtration pressure = hydrostatic pressure - oncotic pressure
NFP = (Pc - Pif) - (pi c - pi if)
if NFP is +, filtration occured
if NFP is -, filtration is occuring
Edema locations?
subcutaneous tissue = peripheral edema
lungs = pulmonary edema
abdominal cavity = ascites
Physical factors that cause edema?
increased venous pressure = increased capillary hydrostatic pressure = increased capillary filtration = edema (due to heart failure or hypertension)
loss of plasma proteins = lower plasma oncotic pressure and lower capillary reabsorption = edema
surgery or radiotherapy = damaged lymph nodes = defective lymph drainage = lymphedema
hypoalbuminemia
occurs:
cirrhosis and hepatitis
increased albumin clearance
pregnancy
results in:
reduced oncotic pressure
less fluid reabsorbed
more fluid in interstitial fluid
edema causes
RV failure = ankle swelling (tissue edema)
LV failure = fluid in lungs (pulmonary edema)
hepatic fibrosis = ascites
