Heller Ch. 6 Flashcards
What are the units for transport rate?
Mass/time
How is transport rate calculated?
Flow rate x concentration (Volume/time) x (mass/volume) = mass/time
What are the four determinants to diffusion?
- The concentration difference
- The surface area of exchange
- The diffusion distance
- The permeability of the capillary wall to the diffusing substance
What two types of pressure influence transcapillary fluid movement?
Hydrostatic pressure Osmotic pressure
Is hydrostatic pressure higher in the interstitial or intracapillary fluid?
Intracapillary (25mmHg) Pc
Interstitial (0mmHg) Pi
What is osmotic pressure?
Hydrostatic pressure necessary to prevent osmotic water movement
What is Oncotic pressure?
Part of osmotic pressure
Particle concentration due to particles that cannot diffuse
Is the oncotic pressure higher in the capillary or in the interstitial fluid?
Capillary (25mmHg) πc
Interstital fluid (0mmHg) πi
What is the effect of the oncotic pressure?
Fluid goes back into the plasma
What is the net filtration rate?
K[(Pc – Pi) – (πc – πi)]
What is the role of the lymphatic system?
To remove large molecules from the interstitial space
Why is it important to remove large molecules from the interstitial space?
A build up in large molecules in the interstitial space would decrease the osmotic pressure difference…fluid would build up
What promotes lymphatic activity?
Increases in interstitial pressure (due to fluid accumulation or to movement to surrounding tissue)
Contractions of the lymphatic vessels…valves prevent back flow
What is the resistance of vessels arranged in parallel?
(1/RT) = (1/R1) + (1/R2) + … + (1/Rn)
What is the resistance of vessels in series?
RT = R1 + R2 + … + Rn
How does blood flow velocity relate to the vessel’s total cross-sectional area?
As the total cross-sectional area increases–i.e. capillaries–the velocity goes down
What is laminar flow?
Orderly, streamlined flow
Little mixing
What causes turbulent flow?
Fluid being forced to move too fast through a narrow opening
What happens as a result of turbulent flow?
Mixing
Sounds–cardiac murmurs, bruits, checking blood pressure
What is the percentage of blood volume in the arteries? Arterioles? Capillaries? and Venules/Veins?
Arteries: 12%
Arterioles: 2%
Capillaries: 5%
Venules/Veins: 60%
Where is the peripheral venous pool?
Veins of the systemic organs
Where is the central venous pool?
Great veins of the thorax
Right atrium
What happens to the blood pressure as blood goes through the different vessels?
Blood pressure decreases to 0 by the time it gets to veins
The vessels are in a series so the resistance increases
What is the resistance across organs?
Organs are in parallel
What is Compliance in relation to volume/pressure?
Compliance is the volume change in response to a pressure change
C = ΔV/ΔP
What is arterial compliance?
Arteries have very little change in volume relative to change in pressure
What is venous compliance?
Veins have a large change in volume relative to the change in pressure
Why is arterial elasticity important for conserving energy?
Expansion during systole and contraction during diastole keeps the blood moving…without relying on the heart pumping
What are Korotkoff sounds?
During auscultation for systolic/diastolic blood pressures
Rely on turbulence caused by collapsed vessels
What is the relationship between arterial pressure, cardiac output, and total peripheral resistance?
PA = CO x TPR
How is mean arterial pressure determined from systolic and diastolic pressures?
PA = PD + 1/3(PS – PD)
What is the relationship between pulse pressure, stroke volume, and arterial compliance?
PP = PS – PD = SV/CA
How does arterial compliance change with age?
Older arteries have a higher pressure change for a given volume changes
What is the effect of constricting venous smooth muscles on venous volume?
There will be a lower volume for a given pressure
