06b: Microcirculation Flashcards
Two primary roles of capillaries.
- Deliver nutrients to tissues
2. Carry metabolites away from tissues
Vasomotion refers to waxing/waning of (X), to increase/decrease flow to (Y).
X = arteriolar tone Y = downstream capillaries
Fewer open capillary beds means (smaller/larger) diffusion distance.
Larger
Fick’s Law of Diffusion state that (X) is equal to:
X = Bulk Flow
D)(A)(deltaC/deltaX
Fick’s law: bulk flow increases with increase in which components?
- D (diffusion coefficient, which decreases with higher MW)
- A (surface area)
- DeltaC (concentration gradient)
Fick’s law: bulk flow increases with decrease in which components?
DeltaX (diffusion distance or path length)
The diffusion coefficient is inversely related to:
Square root of MW
Fick’s Law can be written with permeability as a factor. What’s the equation?
J = PAdeltaC
Diffusion of gases such as O2 and CO2 is primarily controlled by (X), since it takes about (Y) portion of their transit time through capillaries for exchange/equilibration to occur.
X = blood flow through capillary Y = 1/3
T/F: D for O2 is high, but relatively lower for CO2
False - high for both
Certain substances, such as (X) can only enter/exit capillaries through intercellular junctions. This limits the movement, because the junctions are (Y)% of total capillary (Z).
X = glucose, AA Y = 0.2-0.4 Z = surface area
T/F: for most nutrients, diffusion is sufficient as major mechanism to supply tissues.
True
If capillary wall is 0.3 micrometers thick, what’s the (deltaX) value in Fick’s Law?
Unknown - path of molecule not in straight line
Establishing and empirical relationship, using (X), solves the path/distance problem in Fick’s Law. (X) tells us how far molecule will move per (Y).
X = Permeability Y = unit time, unit concentration/pressure gradient, and per surface area
Substance moves through intercellular junction in capillary. It will have (easier/harder) time clearing its path of (X) if it’s a large molecule.
Harder;
X = fluid
(Blood/interstitium) contains high protein concentration with low permeability (proteins can’t leave). Thus, it exerts (X) pressure, which is (in sync/opposed to) hydrostatic pressure.
Blood;
X = oncotic
Opposed to
For bulk flow through capillary, which key pressure gradients should be considered?
Hydrostatic and Oncotic
If net hydrostatic pressure is greater than net oncotic pressure in capillaries, which direction is net fluid movement?
Out of capillaries
If net hydrostatic pressure is less than net oncotic pressure in capillaries, which direction is net fluid movement?
Into capillaries
Hydraulic permeability is defined as (X).
X = permeability of membrane to water
If hydrostatic pressure of interstitial fluid was negative, it would favor which movement?
Favor fluid movement out
Hydrostatic P is initially about (X) mmHg in capillary. If the value is about 4 mmHg in interstitial fluid, what’s the net hydrostatic P? Fluid moves (out/in) as it passes capillary bed.
X = 40;
Net: 36 mmHg
Can’t decide until you know net oncotic P
T/F: Oncotic P in interstitial fluid is 0 mmHg.
False - there is some protein in IF
T/F: Amount of protein in interstitial fluid depends on the tissue.
True
