Midterm 1 - Blood Volume Microcirculation and Fluid Exchange Flashcards

1
Q

what percentage of blood do capillaries contain

A

about 5%

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2
Q

what are capillaries the site of

A

water-nutrients-wastes-gases exchange with interstitial fluid and tissues

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3
Q

how large are capillaries in diameter

A

7-8 um

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4
Q

how long are capillaries

A

0.5 mm

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5
Q

what are red blood cells in diameter

A

approx. 7.5 um

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6
Q

what are capillaries made of

A

a single layer of endothelial cells

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7
Q

what are capillaries formed in

A

dense netowkrs

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8
Q

how close is each cell of a tissue to a capillary

A

within 100 um

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9
Q

where do capillaries receive blood from

A

smallest arterioles and metarterioles

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10
Q

metarterioles

A

connection between arteriole and capillaries network

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11
Q

what does the density of capillaries vary depending on

A

the metabolic activity of the tissue

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12
Q

what do met arterioles possess

A

rings of smooth muscle tissue that can open and close on demand

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13
Q

what are met arterioles doing during exercise

A

all open

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14
Q

what is the consequence of the small diameter

A

a very slow flow

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15
Q

what is resistance reduced by in capillaries

A

the extent of the parallel ramifications

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16
Q

what does trans capillary diffusion depend on

A

capillary type and substance properties

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17
Q

what does transcapillary diffusion follow

A

gradient between blood and interstitial fluid

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18
Q

what do most capillaries have that allow transfer of water and lipid-insoluble molecules

A

pores or clefts

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19
Q

what do the size and number of pores in a capillary depend on

A

the tissue

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20
Q

what type of substances exchange freely across cell membrane

A

lipid soluble (O2 and CO2)

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21
Q

what capillaries are fenestrated

A

intestine
liver
kidney

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22
Q

what does it mean for capillaries to be fenestrated

A

vesicles fuse to form large gaps across endothelial cell membrane

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23
Q

what do fenestrated capillaries allow

A

water and water soluble macromolecules to pass

24
Q

what is bulk flow

A

mass movement of water and dissolves substances through water pores

25
Q

where does bulk flow take place

A

across the capillary walls

26
Q

where is bulk flow filtered

A

towards interstitial fluid (out of blood compartment)

27
Q

where is bulk flow absorbed

A

towards the intravascular fluid (blood)

28
Q

what does bulk flow maintain

A

fluid balance between intravascular and interstitial fluid

29
Q

what is bulk flow dependent on

A

pressure gradients
permeability of vessel
size of diffusion surface
blood flow

30
Q

what pressure gradients is bulk flow dependent on

A

hydrostatic and osmotic

31
Q

hydrostatic pressure

A

filtration pressure - BP inside blood vessels pushes fluid out

32
Q

process of hydrostatic pressure

A

pressure from heart –> arterioles –> capillaries
since pressure in interstitial fluid is close to 0, pushes fluid out of vessel

33
Q

what is colloid osmotic pressure (oncotic)

A

counter balances hydrostatic pressure due to large proteins in that stay in vessel, fluid is reabsorbed

34
Q

what are starling forces

A

net movement of fluid depends on balance between filtration (hydrostatic) and osmotic (oncotic) pressures

35
Q

what pushes fluid out

A

hydrostatic pressure difference

36
Q

what pushes fluid back in

A

osmotic pressure difference

37
Q

what remains constant along capillary length

A

osmotic pressure difference

38
Q

where along the capillary is hydrostatic stronger

A

in the first portion

39
Q

where along the capillary does hydrostatic decrease

A

toward the end - less fluid out, and if hydrostatic < osmotic, fluid moves in

40
Q

what is the net effect of fluid exchange

A

generally accumulation of fluid into interstitial tissue

41
Q

what picks up fluid

A

lymphatic system

42
Q

what is lymphatic drainage

A

the draining of fluid to large veins

43
Q

what happens to fluid that remains in blood

A

collects into venues and goes back to heart

44
Q

what occurs if the lymphatic system cannot keep up with fluid exchange

A

edema formation (filtration exceeds capacity)

45
Q

what is the physiological significance of diffusion

A

nutrient and gas exchange

46
Q

what is the physiological significance of bulk flow

A

stabilize blood volume using interstitial fluid as a buffer

47
Q

physiological significance with blood loss

A

decrease in pressure –> decrease in hydrostatic = fluid enters back

48
Q

physiological significance of excess fluid intake

A

increase in pressure –> increase in hydrostatic –> fluid accumulates in interstitial

49
Q

physiological significance of low protein in plasma

A

decrease in ostmotic –> fluid out

50
Q

physiological significance of high protein in plasma

A

increase in osmotic –> fluid in

51
Q

what is an edema

A

abnormal accumulation of interstitial fluid

52
Q

what are the 4 mechanisms responsible for edemas

A

increase in hydrostatic pressure in blood vessels
increase in interstitial protein concentration
decrease in oncotic pressure
obstruction of lymphatic vessels

53
Q

what can be an effector of increased hydrostatic pressure in blood vessels

A

increase arterial pressure (hypertension)
increased venous pressure (right sided heart failure)

54
Q

what can be an effector of increased interstitial protein concentration

A

inflammation of capillaries, become leaky

55
Q

what can be an effector of decreased oncotic pressure

A

loss of proteins (GI disease)
liver disease
poor diet

56
Q

where do edemas often occur

A

in abdominal cavity
legs due to gravity