Microcirculation Flashcards
Define and give examples of diffusion- limited and flow-limited exchange.
Flow limited exchange is the exchange of small lipid soluble substances across the capillaries. Its only limitation involves the rate of flow of blood moving the molecule into the capillaries. Ex. CO2 and O2
Diffusion- limited exchange is the exchange of lipid insoluble substances across the capillaries. Its limitation across the membrane is determined on the size of the molecule and the permeability. The greater the size, the less permeable a substance is across the capillaries. EX. NACL, Urea, Glucose.
State the importance of capillary hydrostatic pressure.
It tends to force fluids outside the capillaries. It is increased by an decrease in arteriolar resistance and an increase in venous pressure.
State the function of interstitial fluid pressure.
It acts outside and pushed fluid into the capillary membrane. It opposes filtration when the value is positive.
Describe plasma colloid osmotic pressure.
Pressure that opposes filtration causing osmosis of water inward through the membrane. Increased by increase plasma proteins.
Describe interstitial fluid colloid pressure.
Promotes filtration by allowing osmosis of water outward through the capillaries.
Using the components of the Starling equation, explain why fluid does not usually accumulate in the interstitium of the lungs.
Fluid does not usually accumulate in the interstitium of the lungs due to the low capillary hydrostatic pressure coming from the capillaries. Therefore, a low pressure can form an edema. To avoid this, the capillaries sourcing the low production goes through vasoconstriction to force blood flow to the part of the lung that has a high capillary hydrostatic pressure.
Explain how edema develops in response to: a) venous obstruction, b) lymphatic obstruction, c) increased capillary permeability, d) heart failure, e) tissue injury or allergic reaction, and f) malnutrition.
A) Venous obstruction caused an edema due to the increase in outward venous pressure exceeding the inward oncotic pressure.
B) Lymphatic obstruction - an imparted lymphatic drainage caused Edema
C) increased capillary permeability- causes a decrease in capillary oncotic pressure causing edema
D) Heart failure- edema develop from an increase in capillary hydrostatic pressure
E) Increase in hydraulic conductance
F) Malnutrition- edema caused from a decrease in capillary oncotic pressure.
Describe the lymphatics, and explain how the structural characteristics of terminal lymphatics allow the reabsorption of large compounds, such as
proteins.
It returns interstitial fluid back to the heart, allowing reabsorption of large compounds
List the components of Microcirculation.
Arterioles
Venules
Capillaries
Explain the effects of Pc, Pi, πc, πi on the fluid flow, Jv, in the starling equation.
— As Pc and πi increases, Jv increases
— As Pi and πc increase, Jv decreases.
Note: A positive Jv = filtration. A negative Jv = absorption.
