Microcirculation Flashcards

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1
Q

Describe the range of size for arterioles vs meta-arterioles vs capillaries.

A

Arterioles: 5 - 100 micrometers

Meta-arterioles: 10 - 20 Micrometers

Capillaries: 5 - 10 micrometers

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2
Q

What is responsible for the rhythmic oscillatory behavior seen in capillaries?

A

Contraction and relaxation of precapillary vessels

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3
Q

How does transmural pressure affect vasomotion in capillaries?

A
  • Increase in Transmural pressure causes contraction of terminal arterioles
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4
Q

Compare contraction and vasomotion in Large arterioles and metarterioles vs terminal arterioles.

A

Lg Art + MetA —> Do not completely occlude blood flow when constricted

Terminal arterioles —> May arrest blood flow

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5
Q

What is he role of PG12?

A

Prostacyclin: Relaxes vascular smooth muscles via increase in cAMP

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6
Q

How is PG12 made?

A
  • From Arachidonic acid

- PG12 Synthase

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7
Q

How is PG12 released, and how does it work?

A
  • Released by increase in shear stress caused by faster blood flow
  • Inhibits platelet adherence to endothelium, platelet aggregation, and prevents intravascular clot formation
  • relaxation in a secondary function
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8
Q

Describe the function of NO and what causes it’s release.

A
  • Released from endothelial cells stimulated by ACh, ATP, bradykinin, serotonin, substance P, histamine, or shear stress of blood flow
  • Causes endothelium derived vasodilation
  • No dilation in blood vessels lacking endothelium
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9
Q

What is the functioning of Nitroprusside?

A
  • Increases cGMP in vascular smooth muscle

* Not endothelium related

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10
Q

What is the function of endothelin?

A
  • Potential vasoconstrictor

- Affects Vascular the and BP

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11
Q

What is Fick’s Law?

A

Describes diffusion of substances across a membrane

For Capillaries:

J = -PS(Co - Ci)

P = capillary permeability by the substance
S = capillary surface area
Co = concentration of the substance outside the capillary
Ci = concentration of the substance inside the capillary
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12
Q

What is the actions of Bee stings?

A

Alters capillary permeability

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13
Q

What 4 factors most influence capillary diffusion of O2?

A
  1. Diffusion coefficient for O2
  2. Capillary density and diffusion distances
  3. Blood flow
  4. Tissue O2 consumption: O
    2 supply of normal tissue at rest + during activity is not limited by diffusion or by the number of open capillaries
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14
Q

How do capillaries in kidneys, intestines, and lover differ from others such a s skeletal?

A

Kidney/intestine: More porous and very permeable

Liver: Very porous and discontinuous endothelium (fenestrated)

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