My LSS- CVS > CVS 5: Microcirculation > Flashcards

CVS 5: Microcirculation Flashcards

(41 cards)

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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?

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A

Changing the ready of the arterial by neural and hormonal pathways

18
Q

Where in the brain is arterial blood pressure neurally regulated?

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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?

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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

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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?

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A

Deliver metabolic substrate to the cells of the organism

22
Q

What is the thickness of capillary walls

23
Q

What is Fick’s Law?

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A

The factors which enhance diffusion:

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

What is the significance of capillary density?

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A

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

25
Which organs have a high capillary density and why?
Skeletal muscle Myocardium- vulnerable to hypoxia Brain- " Lungs
26
Which tissue has low capillary density?
Adipose tissue- has poor perfusion | Not metabolically active
27
What does skeletal muscle possess to help reduce tissue perfusion during rest?
Pre-capillary sphincters
28
What are the three main types of capillaries?
Continuous Fenestrated Discontinuous
29
Describe the structure of continuous capillaries
- 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
What are fenestrated capillaries?
They are leakier capillaries | Have slightly bigger holes called fenestra allowing bigger substances to go through
31
Describe the structure of discontinuous capillaries and where they are found in the body
- Have large holes in the capillary | - important in the bone marrow where white cells have o get into the blood
32
What is the most common type of capillary structure?
Continuous
33
What sort of capillaries do you get in the blood brain barrier and why?
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
What sort of capillaries do you have in discontinuous blood brain barriers?
Water-filled gap junctions
35
What are the two main factors affecting the movement of fluid in and out of capillaries? And what are these forces known as?
1. Hydrostatic pressure 2. Oncotic pressure STARLING FORCES
36
What is oncotic pressure?
Osmotic force due to plasma proteins drawing water back in
37
Describe the structure of lymph capillaries. What causes the flow of lymph in lymph vessels
- Blind ended - Have valves in lymphatic vessels which means you don't get backwards flow - movement by lymphatic pressure (muscles, lung inflation)
38
Which four places does lymph drain into?
Thoracic duct Right Lymphatic duct Right subclavian vein Left subclavian vein
39
What volume of fluid is returned to the circulatory system each day?
3L
40
What is oedema?
Build up of interstitial fluid when rate of fluid production > rate of lymphatic drainage
41
What might cause oedema?
- Parasitic blockage of lymph nodes (elephantiasis) - removal of lymph nodes - inflammation
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