properties of the vascular system Flashcards

1
Q

two main functions of capillaries

A

solute exchange and fluid exchange

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2
Q

mechanism by which solutes are exchanged

A

diffusion due to concentration gradients across wall

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3
Q

diffusion obeys which law

A

Fick’s law

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4
Q

mechanism by which fluid is exchanged

A

bulk flow due to pressure gradients across the wall

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5
Q

bulk flow obeys which law

A

starling’s principle

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6
Q

explain starling’s principle

A

flow is affected by plasma protein osmotic pressure as well as hydraulic pressure

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7
Q

why does starling’s law apply to capillaries ?

A

they are permeable to water and small solutes

relatively impermeable to plasma proteins

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8
Q

what are the four starling forces?

A

hydrostatic pressure in capillary and interstitial

oncotic pressure in capillary and interstitial

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9
Q

flow at rest

A

5000ml/min

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10
Q

distribution of cardiac output at rest

A

brain- 650ml, 13%

heart- 215ml, 4%

skeletal muscle- 1030, 20%

skin- 430ml, 9%

kidneys- 950ml- 20%

abdominal organs- 1200ml, 24%

other- 525ml, 10%

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11
Q

cardiac output distribution exercise

A

brain- 750ml, 4%

heart- 750ml, 4%

muscle- 12,500ml 73%

skin- 1900, 11%

kidneys- 600ml, 3%

abdominal organs- 600, 3%

other- 400ml, 2%

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12
Q

cardiac output during exercise

A

17,500 ml/min

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13
Q

blood flow definition

A

refers to the movement of blood through vessels

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14
Q

pressure definition

A

a measure of the force that the blood exerts against the vessel walls

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15
Q

which direction does blood flow in?

A

Along a decreasing pressure gradient, from arteries to capillaries to veins

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16
Q

link between velocity of blood flow and cross sectional area

A

velocity of blood flow varies inversely with the total cross sectional area of blood vessels

as the total cross sectional area of vessels increases, the velocity of flow decreases

17
Q

where is blood flow slowest? + benefit

A

slowest in capillaries, allows time for exchange

18
Q

resistance definition

A

force that opposes the flow of a fluid

19
Q

in blood vessels, what causes most of the resistance?

A

vessel diamater

20
Q

link between blood flow, diameter and resistance

A

as the diameter decreases, the resistance increases and the blood flow decreases

21
Q

difference between flow rate and velocity

A

velocity is the speed

flow rate is the volume of fluid passing through an area

22
Q

how else can flow rate be increased?

A

increasing the diameter

23
Q

viscosity definition

A

the thickness of fluids that affects their ability to flow

24
Q

viscosity relationship with resistance and flow

A

directly proportional to resistance

inversely proportional to flow

the thicker the blood, the slower the flow, the greater the resistance

25
anomalous viscosity of blood explained
red blood cells can deform and aggregate, thus viscosity of blood can vary with sheer rate blood becomes less viscous at high rates, as the blood cells aggregate