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My LSS- CVS > CVS 5: Microcirculation > Flashcards

CVS 5: Microcirculation Flashcards

1
Q

What are post-capillary venues also known as?

A

Pericytic venules

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2
Q

What is Blood flow rate?

A

Volume of blood passing through a vessel per unit time

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3
Q

What is the equation for flow rate?

A

Flow= delta P (pressrure gradient) / R (vascular resistance)

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4
Q

What is resistance?

A

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

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5
Q

Give three factors which affect resistance

A
  1. Blood Viscosity
  2. Vessel Radius
  3. Vessel Length
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6
Q

Give the equation for resistance

A

R= 1/r^4

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7
Q

How d you determine the pressure gradient?

A

Difference in pressure between arterial pressure and pressure in the capillary bed

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8
Q

What is the normal blood pressure also called?

A

Mean Arterial Pressure (MAP)= blood pressure in many artery around the body

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9
Q

What is the significance of the capillary beds?

A

Blood flows more slowly= Blood pressure decreases
More exchange of nutrients
more diluted= lower blood pressure

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10
Q

How can you find the flow rate in an organ?

A

MAP/ Resistance of the organ

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11
Q

How is vasodilation and vasoconstriction achieved?

A
  • Arteriolar smooth muscle is in a state of partial constriction= VASCULAR TONE
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12
Q

What are the two functions of changing the radii of arterioles?

A
  1. Match blood low to metabolic needs of specific tissue (local intrinsic control)
  2. Help regulate arterial blood pressure (extrinsic control)
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13
Q

Give an example of arterioles responding to changes to the chemical environment

A

ACTIVE HYPERAEMIA

  • muscle becomes more active
  • metabolism increases and O2 consumption increases
  • change is detected in the tissues–> signal sent to arterioles–> vasodilation
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14
Q

Define Active hyperaemia

A

Increase in organ blood flow that is associated with increased metabolic activity of that tissue or organ

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15
Q

Give an example of arterioles responding to the physical environment

A

Placing an ICEPACK on muscle

  • tissue senses fall in temp
  • arteriolar smooth muscle contracts so less blood reaches surface and less heat lost through radiation
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16
Q

What is the equation for applying F= dP/R to the whole circulation?

A

CO= MAP/ TPR

  • MAP because delta P= change in arterial and venous pressure and venous pressure is basically 0
  • TPR= sum of resistance in all arterioles in the body

MAP= CO x TPR

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17
Q

How is arterial blood pressure regulated?

A

Changing the ready of the arterial by neural and hormonal pathways

18
Q

Where in the brain is arterial blood pressure neurally regulated?

A
  • Regulated by Cardiovascular control centre in the medulla
19
Q

Which receptors in the medulla sense arterial blood pressure and which cells cause dilation and constriction?

A

ADRENORECEPTORS
Alpha- constriction
Beta- dilation

20
Q

What are the two methods of hormonally regulating the arterial blood pressure and give examples of hormones for each of the mechanisms

A
  1. Vasoconstrictors= increase in TPR
    a. Vasopressin
    b. Angiotensin II
  2. Increasing Sympathetic activity= increase in CO
    a. Adrenaline/ Noradrenaline
21
Q

What is the function of capillaries?

A

Deliver metabolic substrate to the cells of the organism

22
Q

What is the thickness of capillary walls

A

1 micrometer

23
Q

What is Fick’s Law?

A

The factors which enhance diffusion:

  • minimise diffusion distance
  • maximise surface area
  • maximise diffusion time
24
Q

What is the significance of capillary density?

A

The more metabolically demanding a tissue is, the greater the tissue density

25
Q

Which organs have a high capillary density and why?

A

Skeletal muscle
Myocardium- vulnerable to hypoxia
Brain- “
Lungs

26
Q

Which tissue has low capillary density?

A

Adipose tissue- has poor perfusion

Not metabolically active

27
Q

What does skeletal muscle possess to help reduce tissue perfusion during rest?

A

Pre-capillary sphincters

28
Q

What are the three main types of capillaries?

A

Continuous
Fenestrated
Discontinuous

29
Q

Describe the structure of continuous capillaries

A
  • have small water-filled gap junctions between the endothelial cells
  • allows passage of electrolytes and small molecules
  • most substances move through the endothelial cells
30
Q

What are fenestrated capillaries?

A

They are leakier capillaries

Have slightly bigger holes called fenestra allowing bigger substances to go through

31
Q

Describe the structure of discontinuous capillaries and where they are found in the body

A
  • Have large holes in the capillary

- important in the bone marrow where white cells have o get into the blood

32
Q

What is the most common type of capillary structure?

A

Continuous

33
Q

What sort of capillaries do you get in the blood brain barrier and why?

A

Continuous capillaries but DO NOT have water- filled gap junctions but have really tight gap junction
= access of substances to the brain is tightly regulated
Anything that wants to cross has to diffuse across the endothelial cell

34
Q

What sort of capillaries do you have in discontinuous blood brain barriers?

A

Water-filled gap junctions

35
Q

What are the two main factors affecting the movement of fluid in and out of capillaries? And what are these forces known as?

A
  1. Hydrostatic pressure
  2. Oncotic pressure
    STARLING FORCES
36
Q

What is oncotic pressure?

A

Osmotic force due to plasma proteins drawing water back in

37
Q

Describe the structure of lymph capillaries. What causes the flow of lymph in lymph vessels

A
  • Blind ended
  • Have valves in lymphatic vessels which means you don’t get backwards flow
  • movement by lymphatic pressure (muscles, lung inflation)
38
Q

Which four places does lymph drain into?

A

Thoracic duct
Right Lymphatic duct
Right subclavian vein
Left subclavian vein

39
Q

What volume of fluid is returned to the circulatory system each day?

A

3L

40
Q

What is oedema?

A

Build up of interstitial fluid when rate of fluid production > rate of lymphatic drainage

41
Q

What might cause oedema?

A
  • Parasitic blockage of lymph nodes (elephantiasis)
  • removal of lymph nodes
  • inflammation

My LSS- CVS (21 decks)

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