Phys Lecture 6: Microcirculation Flashcards
How is blood flow regulated through the capillaries?
sphincters
How does CO2 and O2 pass thru the capillary wall?
diffusion
How does water and small solutes pass thru the capillary wall?
clefts
How do plasma proteins pass thru capillary wall?
fenestrations in wall
How do large molecules pass thru capillary wall?
endocytosis
What does a reflection coefficient close to 1 mean?
that molecules is impermeable to the capillary endothelium
What does a permeability coefficient of 1 mean?
that the molecule is permeable to the capillary wall
How would the reflection coef change in an inflammatory state such as a burn?
would decrease (<1) *proteins are allowed to flow through
What is the starling equation?
flow = Kf x [(HPc-HPi) - (OPc-OPi)]
What are the positive pressures?
those that favor filtration:
-high HPc and low OPc
What are the negative pressures?
those the favor abs into capillary:
-High OPc an low HPc ??
In the arterial side of capillaries, there is normally net ____
filtration/movement of fluid into interstitial space
In the venous side of capillaries, there is normally net ____
absorption/movement of fluid into capillaries
Describe the starling forces along the length of capillaries and how that effects blood flow…
OP is constant but HP is higher at arterial end then venous = net pressure is higher at arterial end then venous… blood flows from high to low pressure = blood always flows from arterial to venous
**also the filtration pressure > abs pressure = more net filtration than abs
What is the relationship between Kf and R?
Kf = 1/R
* inc R -> dec Kf
How is Kf and R diff for a fenestrated endothelium and a continuous endothelium?
fenestrated has more permeability = higher Kf and lower R
What effect on filtration/abs does inc the HP on the arterial end of a capillary have?
inc filtration
What effect on filtration/abs does inc the HP on the venous end of a capillary have?
inc filtration
By definition, edema forms when…
the volume of interstitial fluid (due to filtration out of the capillaries) exceeds the ability of the lymphatics to return it to the circulation
What determines ISFV?
fluid filtration from capillaries (input)
fluid drainage in lymphatic vessels (output)
How do the starling forces change to cause edema?
HPc inc and OPc dec
What direction does Kf move (up or down) to cause edema.
up/increases
Does inc or dec in lymphatic drainage/flow cause edema
decrease (lymphatic drainage = ISFV output)
What opposes the effects of inc capillary filtration?
lymphatic system/drainage if ISFV in lymphatic vessels to return to to venous circulation
How does the anatomy of the lymphatic system/vessels favor absorption of fluid from ISF?
contraction of the valves in the vessels pushes the fluid through the vessels
–>the vessels create negative pressure (low HP in vessel) which allows them to act like a sponge to pick up fluid in ISF
How does edema develop? (what is the number given to us too)
when the fluid entry into interstitium»_space;» fluid removal by lymph
*WHen ISF pressure > 5 or 6 mmHg, the lymph flow plateaus
Describe how ISFV is maintained when there is an inc in ISFV.
Inc ISFV –> inc the HPi with opposes net filtration (HPc-HPi) = less fluid is filtered fromt he capillaries into the ISF
Increase in _____ pressure causes edema. What can cause this to increase?
HPc
- heart failure
- venous obstruction
- inflammation (local vasodilation)
OPi:
- lymph obstruction
- inflammation (leakage of shit into ISF)
Decrease in _____ pressure causes edema. What can cause this to increase?
OPc
- liver disease
- malnutrition
- kidney disease (nephrotic syndrome)
Inc in Kf can cause edema, what causes inc in Kf?
increased in capillary permeability:
- inflammation (burns)
- inc surface area + local vasodialtion
- reduced reflection coef = inc permeability
