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cardiovascular system > Microcirculation > Flashcards

Microcirculation Flashcards

1
Q

features of the microcirculation

A

1st order arteriole with smooth muscle (bring substances to capillaries)
terminal arteriole
precapillary sphincter
capillaries (exchange)
pericytic venule
venule (substances deposited then blood leaves the tissue)

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2
Q

microvasculature differences between organs

A

specific to each organ

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3
Q

aim of CVS

A

adequate blood flow through the capillaries

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4
Q

what is the blood flow rate

A

volume of blood passing through a vessel (and to the tissue) per unit time

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5
Q

what is Darcy’s law

A

pressure gradient = flow rate *resistance

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6
Q

flow rate =

A

pressure gradient/resistance

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7
Q

pressure gradient =

A

pressure A - Pressure B

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8
Q

where is pressure A and B

A

A - start of arteriole

B leaving arteriole - determines how much blood flows through the capillaries

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9
Q

affect of increasing pressure gradient

A

increase blood flow

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10
Q

what is resistance

A

Hinderance to the blood flow due to friction between moving fluid and stationary vascular walls

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11
Q

variation in vessel length and blood viscosity

A

very slow changes

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12
Q

variation in vessel radius

A

change in seconds - has a major effect on resistance

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13
Q

affect of increasing blood pressure on pressure gradient, resistance and flow

A

P - increase
R - no change
F - increase

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14
Q

affect of arteriolar vasoconstriction on pressure gradient, resistance and flow

A

P - no change
R - increase
F - decrease

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15
Q

MAP entering arterioles

A

99mmHg

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16
Q

MAP leaving arterioles

A

37mmHg

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17
Q

affect of arterioles

A

huge pressure drop from 1 side to the other

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18
Q

pressure gradient in arterioles

A

pressure in = MAP
out - low mmHg
therefore pressure gradient = MAP
without it - blood wouldn’t reach capillaries

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19
Q

in arterioles flow(organ) =

A

MAP/R(overall)

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20
Q

affect of contraction on radius, resistance and flow

A

r - decrease
R - increase
F - decrease

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21
Q

affect of relactation on radius, resistance and flow

A

r - increase
R - decrease
F - increase

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22
Q

why does arteriolar smooth muscle normally display partial contraction

A

so either further dilation/contraction can take place

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23
Q

why are the radius of arterioles changed

A

1 - match blood flow to metabolic needs - intrinsic controls, main function. Each tissue regulate arteriolar muscle based on conditions in that tissue
2 - help regulate systemic arterial pressure - extrinsic control via nerves/blood

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24
Q

how are chemicals used to match blood flow to metabolic needs

A

there is an increase in metabolite production and oxygen usage
bv react to local change
more blood flow - vasodilation
ACTIVE HYPERAEMIA

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25
Q

how is blood flow matched to metabolic needs using physical methods

A

decrease in temp/increase in stretch due to increase in bp
reduce flow to skin arterioles
eg add cool to stop swelling
MYOGENIC AUTOREGULATION

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26
Q

effect of autoregulation when Bp is increased

A

there is a change in pressure gradient in every tissue - not enough blood to perfuse all of the tissues
with no autoregulation - flow increases and resistnace decreases
with autoregulation - R increases and flow decreases

27
Q

skeletal muscle arterioles response during exercise

A

active hyperaemia

28
Q

small intestine arterioles response during exercise

A

myogenic vasoconstriction

increased pressure - these arterioles don’t need it son reduce the blood flow

29
Q

CO =

A

MAP/total peripheral resistance

30
Q

MAP =

A

CO*TPR

31
Q

how do arterioles regulate arterial bp via neurons

A

nervous and hormonal control
nerves from cardiovascular control centre in the medulla
predominantly cause vasoconstriction
if you vasoconstrict and increase resistance and pressure decreases flow to specific organs
if you lose a lot of blood - vasoconstriction of all vessels - negative consequences if long termn

32
Q

how do arterioles regulate arterial bp via hormones

A

ADH(vasopressin), angiotensin II and adrenaline/noradrenaline cause vasoconstriction

33
Q

other action of Ang II

A

preserves water

34
Q

relationship between neuronal and hormonal control of Bp

A

work together in times of need

focussed on ensuring flow to the brain

35
Q

what is the purpose of capillary exchange

A

delivery of metabolic substrates to the cells of the organism

36
Q

why is capillary density important

A

ensures that every cell is relatively close to the capillaries
highly metabolic capillaries have denser capillary networks

37
Q

what are capillaries designed for

A

to enhance diffusion - Fick’s law
minimise distance
maximise the SA - branching

38
Q

3 most heavily perfused tissues with capillaries

A

lung 3500cm2/g
brain/myocardium 500
skeletal muscle 100

39
Q

what are precapillary sphincters

A

allow some capillaries to be shut down - eg skeletal muscles have a huge capacity but limited flow at rest, at exercise they take a lot of output

40
Q

tissue with low capillary density

A

adipose

41
Q

describe continuous capillaries

A

most common

small water filled gap junction

42
Q

transport through continuous capillaries

A

if lipid soluble - pass through the cell
if small - pass through gap junction
if big - need mechanism to travel through cell eg channel

43
Q

describe fenestrated capillaries

A

filter stuff of a certain size - in glomerulus of kidney
stiff ends up in the urine
P-glycoprotein transporter kick stuff out of the capillaries
if water soluble a mechanism is needed
if really lipid soluble - enter the brain
fenestrae 80nm

44
Q

location of fenestrated capillaries

A

glomerulus in kidney

45
Q

describe discontinuous blood flow

A

very large gaps

46
Q

where are there discontinuous capillaries

A

bone marrow - WBC need to enter blood

liver - need to metabolise lots of things - need substances to be able to easily access liver tissue

47
Q

type of capillary that forms the blood brain barrier

A

continuous with tight junctions instead of gap junctions

tighter control of what enters and leaves the cell

48
Q

what is a leaky blood brain barrier

A

normal continuous structure

access and sample blood easier

49
Q

describe fluid movement in capillaries

A

bp force fluid through capillaries
fluid squeezed into tissues
protein free plasma leaves the bv, mixes with interstitial fluid and is reabsorbed - bulk flow
if lost all blood vol and pressure would decrease so need counter force to draw fluid in
oncotic pressure in blood (plasma proteins) not in interstitial fluid
starling’s forces

50
Q

what does the hydrostatic force do

A

push out of the capillaries

51
Q

what does the oncotic force do

A

pull into the capillaries

osmotic oressure caused by proteins

52
Q

explain the balance between hydrostatic and oncotic forces

A

if pressure in capillary is bigger than in interstitial fluid - untrafiltration - ie fluid out
if inward driving pressure hogher than outward driving pressure - reabsorption - fluid in

53
Q

why is oncotic pressure stable

A

protein composition doesn’t change

54
Q

change in hydrostatic pressure down the capillary

A

it decreases

55
Q

what is the result of ultrafiltration being more effective than reabsorption

A

always losing blood from the system
without mechanism fluid would be lost
role of lymphatic system
change of 1

56
Q

describe the lymphatic system

A

wherever a blood capillary is there is a lymphatic capillary
lymph capillaries are blind ending
fluid diffuses into a lymphatic flap - allow fluid in but don’t let it out

57
Q

features of the lymphatic system

A 
lymphatic endothelium 
anchoring filament 
interstitial fluid 
opening 
lymphatic capillary
58
Q

other role of lymphatic system

A

immune surveillance mechanism

fluid through lymphatic system - stimulate lymphocyte production in lymph nodes

59
Q

structure of the lymphatic system

A

no pump for flow
drain from R lymphatic duct to thoracic duct
and into the R and L subclavian valves
here there is a close connection to vein - deposit in the venous system
3L a day

60
Q

limitations with the lymphatic system

A

if rate of production of fluid is highe than the rate of drainage - then oedema
elephantiasis - parasitic blockage of lymph node
tissue damage - inflammation, capillaries leakier, more fluid is forced into the tissue so can’t be drained properly

61
Q

how does vessel length increase resistance

A

more of the vessel for the blood to make contact with

62
Q

what is cardiac output

A

blood flow - amout of blood out

63
Q

what in total peripheral resistance

A

store of resistance in every tissue - total resistance in system

cardiovascular system (22 decks)

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