Peripheral Vascular System--Nordgren Flashcards
Net movement into capillary
reabsorption
Net movement out of capillary
filtration
2 types of pressure affecting movement through capillary walls
hydrostatic pressure (P): due to pressure
oncotic pressure (π): due to concentration of proteins, usually higher in capillaries
Starling hypothesis
Net filtration rate = K[(Pc-Pi)-(πc-πi)]
i = intersitial fluid
Positive net pressure gradient indicates
filtration
Negative net pressure gradient indicates
reabsorption
Where does filtration occur in capillaries?
arterial end
Where does reabsorption occur in capillaries?
venous end
Why does filtration occur on arteriole end and reabsorption occur on venule end of capillaries?
decrease in hydrostatic pressure across capillary
What does histamine do to capillaries?
makes them more leaky, proteins leak out and Starling forces dictate even more leaky capillaries –> less reabosorption
What removes the proteins from the interstitial fluid?
lymphatic system
Resistance of series calculation
Rs = R1 + R2 + ….
Resistance of parallel network calculation
total radius of all elements put together
1/Rp = 1/R1 + 1/R2 + …
Why does the velocity of blood through the capillaries slow compared to the arteries?
capillaries have a higher combined cross sectional area
How can peripheral veins increase cardiac output?
contriction leads to increased preload
What is the central venous pressure normal value
~0 mmHg
Which piece of vasculature has the highest resistance to flow?
arterioles
Total Peripheral Resistance Equation
(TPR)
calculated in parallel!
adding organ to system will decrease resistance
removing organ from system will increase resistance
What is compliancy?
ability of veins to stretch
accomidates increases in volume
C = ΔV/ΔP
Arteries have low compliancy
pressure resivours
small change in volume leads to high pressure change
elastic bounceback pushes blood through vasculature
Mean Arterial Pressure
PA = CO x TPR
MAP = PD + 1/3 PP
MAP = 2/3 PD + 1/3 PS
Greater compliance affects PP how?
greater compliance
–> less PP
