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cardiovascular system > Microcirculation > Flashcards

Microcirculation Flashcards

(63 cards)

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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
how is blood flow matched to metabolic needs using physical methods
decrease in temp/increase in stretch due to increase in bp reduce flow to skin arterioles eg add cool to stop swelling MYOGENIC AUTOREGULATION
26
effect of autoregulation when Bp is increased
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
skeletal muscle arterioles response during exercise
active hyperaemia
28
small intestine arterioles response during exercise
myogenic vasoconstriction | increased pressure - these arterioles don't need it son reduce the blood flow
29
CO =
MAP/total peripheral resistance
30
MAP =
CO*TPR
31
how do arterioles regulate arterial bp via neurons
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
how do arterioles regulate arterial bp via hormones
ADH(vasopressin), angiotensin II and adrenaline/noradrenaline cause vasoconstriction
33
other action of Ang II
preserves water
34
relationship between neuronal and hormonal control of Bp
work together in times of need | focussed on ensuring flow to the brain
35
what is the purpose of capillary exchange
delivery of metabolic substrates to the cells of the organism
36
why is capillary density important
ensures that every cell is relatively close to the capillaries highly metabolic capillaries have denser capillary networks
37
what are capillaries designed for
to enhance diffusion - Fick's law minimise distance maximise the SA - branching
38
3 most heavily perfused tissues with capillaries
lung 3500cm2/g brain/myocardium 500 skeletal muscle 100
39
what are precapillary sphincters
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
tissue with low capillary density
adipose
41
describe continuous capillaries
most common | small water filled gap junction
42
transport through continuous capillaries
if lipid soluble - pass through the cell if small - pass through gap junction if big - need mechanism to travel through cell eg channel
43
describe fenestrated capillaries
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
location of fenestrated capillaries
glomerulus in kidney
45
describe discontinuous blood flow
very large gaps
46
where are there discontinuous capillaries
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
type of capillary that forms the blood brain barrier
continuous with tight junctions instead of gap junctions | tighter control of what enters and leaves the cell
48
what is a leaky blood brain barrier
normal continuous structure | access and sample blood easier
49
describe fluid movement in capillaries
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
what does the hydrostatic force do
push out of the capillaries
51
what does the oncotic force do
pull into the capillaries | osmotic oressure caused by proteins
52
explain the balance between hydrostatic and oncotic forces
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
why is oncotic pressure stable
protein composition doesn't change
54
change in hydrostatic pressure down the capillary
it decreases
55
what is the result of ultrafiltration being more effective than reabsorption
always losing blood from the system without mechanism fluid would be lost role of lymphatic system change of 1
56
describe the lymphatic system
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
features of the lymphatic system
``` lymphatic endothelium anchoring filament interstitial fluid opening lymphatic capillary ```
58
other role of lymphatic system
immune surveillance mechanism | fluid through lymphatic system - stimulate lymphocyte production in lymph nodes
59
structure of the lymphatic system
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
limitations with the lymphatic system
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
how does vessel length increase resistance
more of the vessel for the blood to make contact with
62
what is cardiac output
blood flow - amout of blood out
63
what in total peripheral resistance
store of resistance in every tissue - total resistance in system

cardiovascular system (22 decks)

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