Chapter 6: The Peripheral Vascular System Flashcards
What are the factors affecting transcapillary solute diffusion (4)?
- solute concentration gradient
- surface area
- thickness
- permeability to the solute
What is the inside diameter and wall thickness of capillaries?
5 micrometer
1 micrometer
What does the capillary wall consist of?
just one layer of endothelial cells
How do small polar particles cross the capillary membranes?
through pores between endothelial cells
Name an organ with tight capillaries and one that has more leaky capillaries
- brain tight
- kidneys leaky
What is the diameter of capillary pores?
40 A
Name 4 other functions of capillaries/endothelial cells than diffusing water and solutes
- activation (enzymatic convertion) of circulating hormones
- angiogenesis and remodeling of vasculature
- hemostasis - produce factors and initiate primary hemostasis from injury
- produce vasoactive substanes to control arteriole diameter
What is the normal hydrostatic and colloid osmotic pressure within the capillaries? What are they in the interstitium?
25 both
close to 0 in the interstitium
How is osmotic pressure defined?
the hydrostatic pressure needed to oppose the osmotic pulled created if compartments were separated by a membrane only permeable to water
List the traditional starlings equation
Efflux = Kfiltration (hydrostic pressure capillary - hydrostatic pressure interstitium) - (oncotic pressure capillary - oncotic pressure interstitium)
How does histamine release causer interstitial edema?
causes increased permeability of endothelial wall –> increased protein efflux –> increased interstitial oncotic pressure –> fluid efflux
How does capillary filtration change during hemorrhagic shock?
volume depletion will lead to a decreased hydrostatic pressure in capillaries –> favor net movement of water from the interstitium to the capillaries
What promotes the forward flow of lymphatic drainage?
pressure gradient –> interstitial tissue pressure increases with fluid accumulation or movement
active contraction of lymphatic vessels
have one way valves to prevent back-flow
Explain how resistance is calculated in a network of parallel vessels
in a parallel network the additional vessel will reduce the overall resistance as the cross-sectional area increases
1/Rn = 1/R1 + 1/R2 + 1R3 …
Describe how the velocity is distributed in laminar flow through vessels
highest velocity in the center of the flow –> reduced towards the periphery
i.e., parabolic velocity profile
Which vessels have the highest flow velocity?
aorta, arteries
What is the percentage of blood volume in:
* pulmonary system and heart chambers
* arteries
* arterioles
* capillaries
* venules and veins
- 20%
- 12%
- 2%
- 5%
- 60%
Which vessels have the highest vascular resistance and hence the largest pressure drop?
arterioles
As arteries become more distant to the heart, how does their pulse pressure change?
increases
What is a normal central venous pressure?
0
How does arteriolar vasoconstriction or vasodilation affect transcapillary flux?
vasoconstiction - decreases capillary pressure –> hydrostatic pressure is low and favors flow of water back into the capillaries from the interstitium
reverse for vasodilation
How is compliance defined?
compliance = volume change / pressure change
How does the arterial pressure not drop to zero/0 during diastole?
because of the elastic recoil –> arteries are stretched during systole and the energy produced by the recoil sustains forward flow and pressure during diastole
How can you use flow and resistance to calculate MAP?
MAP = CO x SVR
Name the equation to calculate MAP from SAP and DAP
MAP = DAP + (SAP-DAP)/3
What are the main determinants of the pulse pressure, and which of these is usually affecting the pulse pressure actuley?
- arterial compliance
- SV
arterial compliance is very stable –> usually changes in PP are caused by changes in SV
