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LSS: cardiovascular system > lecture 7: microcirculation > Flashcards

lecture 7: microcirculation Flashcards

1
Q

what is the arterial flow of blood ?

A

first order arterioles
terminal arterioles
capillaries

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2
Q

what is the venous flow of blood?

A

post capillary venues
venues
veins

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3
Q

hat is the blood flow rate?

A

how much blood is passing through a vessel at any given time?

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4
Q

what is the equation of flow?

A

flow = change in pressure / resistance

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5
Q

what is change in pressure?

A

Mean Arterial Pressure

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6
Q

what is resistance of blood dependent on?

A
  • blood viscosity
  • vessel length
  • vessel radius - MOST IMPORTANT
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7
Q

what is the major determinant of the blood flow?

A
  • resistance of the arterioles in the organ
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8
Q

how is blood flow affected diagram ?

A

INSERT DIAGRAM

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9
Q

what is the mean arterial pressure entering the arteries?

A

93 mmHg

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10
Q

what is the mean arterial pressure of the blood leaving arterioles?

A

37 mmHg

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11
Q

what is vascular tone?

A

– the state of partial vasoconstriction that arteriolar

smooth muscle displays to allow constriction AND dilation if needs be.

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12
Q

what is a pressure gradient ?

A

pressure A (blood entering ) - pressure B (blood leaving)

without the pressure difference the blood would not reach tissue capillary beds

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13
Q

what is poiseulles law?

A

R is proportional to 1/r^4

r radius
R resistance

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14
Q

what are the functions of the adjusting of the radius of arterioles?

A
  • matching the blood flow to the metabolic needs of the tissue (regulated intrinsically by the tissue)
  • to help regulate the arterial blood pressure
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15
Q

how is the blood flow matched to the metabolic needs of the tissue?

A

a. chemical responses
- >the muscle becomes more metabolically active
- > the o2 usage increases
- > vasodilation happens
- > this is active hyperaemia

b. physical environment - > the tissue responds to local changes in temp
- > vasoconstriction happens so less heat is lost in the blood flow \
- > this is auto regulation

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16
Q

what is active hyperaemia?

A

an increase in organ blood flow that is associated with increased metabolic
activity of an organ or tissue.

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17
Q

what is auto regulation?

A

raised BP increases stretch on cells which stimulates myogenic vasoconstriction.

18
Q

what is an equation linking cardiac output, blood pressure and total resistance

A

cardiac output = blood pressure / total resistance

19
Q

what are the two ways that arterial blood pressure is regulated extrinsically?

A

neural - regulated by cardiovascular control centre in the medulla
hormonal

20
Q

how does neural regulation work?

A
  • regulated by cardiovascular control centre in the medulla
    1. to increase BP, vasoconstriction happens
    2. the adrenoreceptors facilitate constriction and dilation
21
Q

how does hormonal regulation work?

A
  • the brain mimics Sympathetic nervous system

1. different hormones like vasopressin , angiotensin ii and noradrenaline help regulate arterial BP

22
Q

how wide are capilleries ?

how thick are capillaries ?

A

7 micrometers

1 micrometer

23
Q

why is capillary density important?

A

every cell in the body needs to be close to a capillary to deliver O2, glucose ect.

24
Q

what is ficks law

A

emphasising minimising diffusion distance and time and maximising surface area

25
Q

which tissues have the greatest capillary density?

A
  • skeletal muscle
  • myocardium muscle
  • brain
  • lungs
    they need a lot of oxygen
26
Q

what does the skeletal muscle do in absence of exercise?

A

the skeletal muscle shuts off the majority of its capillaries via the pre capillary sphincters in absence of exercise

27
Q

what are the three types of capillaries?

A
  • continous
    small water filled gap junctions to allow passage of electrolytes
  • fenestrated
    have holes called fenestrae
  • discontinuous
  • large holes with passage for bigger cells like
    leukocytes in the bone marrow
    also in the liver
28
Q

what is the blood brain barrier an example of?

A

continuous
- there are very very tight gap junctions

(there are some parts of the brain with a leaky good brain barrier which is just normal continuous capillary walls)

29
Q

what is bulk flow?

A

a volume of protein-free plasma filters out of
the capillary, mixes with surrounding interstitial fluid (IF)
and is then reabsorbed

30
Q

what forces the plasma out?

A
  • hydrostatic pressure (from the heart)
  • oncotic pressure
    (from the osmotic pressure)
31
Q

what is ultrafiltration?

A
  • at the arteriolar end the pressure inside the capillary is bigger than the pressure in the interstitial space
32
Q

what is reabsorption?

A

at the venous end the pressure in the interstitial fluid is more than the hydrostatic pressure in the capillary

33
Q

what is the significance of the fact that ultra filtration is more effective than reabsorption?

A
  • this means some fluid is NOT reabsorbed so the extra fluid goes to the lymphatic fluid

we are always losing fluid

34
Q

what are lymphatic vessels like?

A

they are blind ended not a closed loop like blood vessels

35
Q

what does the lymphatic system have?

A

one way valves to prevent back flow

36
Q

what drives the lymphatic system?

A
  • muscle pressures

- thoracic cavity pressures

37
Q

what are key roles of lymphatic system

A
  • to get excess fluid, which was not reabsorbed, back into the blood
  • immunity
38
Q

what does the lymph drain into?

A
  • thoracic duct
  • right lymphatic duct
  • right subclavian vein
  • left subclavian vein
39
Q

what is oedema?

A
  • if the amount of lymph produced is greater than the rate of removal of the fluid
40
Q

what might cause oedema?

A
  • this is caused by parasitic blockage of the lymph nodes

elephantiasis

LSS: cardiovascular system (17 decks)

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