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SF3- EXAM 2 > Pulmonary Circulation > Flashcards

Pulmonary Circulation Flashcards

1
Q

Pulmonary circulation has low resistance and systemic circulation has high resistance. What qualities of both determine the level of resistance?

A

Pulmonary

  • Arterioles have less smooth muscle
  • Veins are wider and shorter
  • Pulmonary vessel walls are thinner

Systemic

  • Increased smooth muscle in the arterioles & the metarterioles.
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2
Q

Compare pulmonary and systemic circulation, in terms of preesure, resistance, and compliance.

A

Pulmonary

  • Pressure: LOW
  • Resistance: LOW
  • Compliance: HIGH

Systemic

  • Pressure: HIGH
  • Resistance: HIGH
  • Compliance: LOW
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3
Q

At rest, aorta pressure is approximately 95 mmHg. Why is it so high?

A

Because systemic capillaries are closed

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4
Q

During systemic circulation, what is the approximate pressure of the aorta and right atrium?

A

Aorta: 95 mmHg

Right atrium: 2 mmHg

*This makes the driving pressure aprroximately 93 mmHg

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5
Q

During pulmonary circulation, what is the approximate pressure of the pulmonary artery and left atrium, respectively?

A

Pulmonary artery: 15 mmHg

Left atrium: 8 mmHg

*This makes the net driving pressure approximately 7 mmHg

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6
Q

How is pulmonary vascular resistance calculated?

A

PVR= (MPAP-MLAP)/(PBF)

MPAP= Mean pulmonary artery pressure

MLAP= Mean left atrial pressure

PBF= Pulmonary blood flow

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7
Q

Why is pulmonary resistance so much lower than systemic resistance?

A
  • Pulmonary blood vessels are shorter and wider than those in the systemic circulation
  • Arterioles are also present in much higher numbers
  • The pulmonary arterioles are less muscular than those in the systemic circulation
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8
Q

Which passive factors play a major role in pulmonary vascular resistance?

A
  • Gravity
  • Body position
  • Lung volume
  • Alveolar and intrapleural pressures
  • Intravascular pressures
  • Right ventricular output

NOTE: These factors play a major role in pulmonary vascular resistance without altering the tone of the pulmonary vascular smooth muscle

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9
Q

Transmural pressure difference

A

Pressure inside minus pressure outside the vessel

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10
Q

As transmural pressure difference ________ (increases/decreases), the vessel diameter increases and resistance falls.

A

Increases

NOTE: A negative transmural pressure difference can lead to compression or even collapse of the vessel.

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11
Q

More _______ (negative/positive) intrapleural pressure pulls open extra-alveolar vessels.

A

Negative

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12
Q

Alveolar vessel resistance is dependent on what two factors?

A

Transmural pressure

Lung volume

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13
Q

As lung volume __________ (increases/decreases), the alveolar walls become more stretched out.

A

Increases

NOTE: The alveolar vessel is stretched along the longitudinal axis and the alveolar vessel is crussed when viewed in cross-section. This raises vessel resistance

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14
Q

Pulmonary vascular resistance is lowest near the __________ and increases at both low and high lung volumes because of the combined effects of the alveolar and extralveolar vessels.

A

Functional residual capacity

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15
Q

How are low lung volumes achieved?

A
  • Positive intrapleural pressures
  • Compression of extraalveolar vessels
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16
Q

Total pulmonary vascular resistance

A

Extra-alveolar resistance + alveolar resistance

17
Q

Functional Residual Capacity

A

The volume of air present in the lungs at the end of passive expiration.

18
Q

Resistance to blood flow is higher at ______ (low/high) lung volumes because the traction on the vessel walls is decreased.

A

Low

19
Q

Gravity-dependent Pulmonary Blood Flow in the Lung

A

Blood flow to alveoli is greater at the bottom of the lung than at the top, when in an upright position

NOTE: Blood travels through the more gravity-dependent regions of the lung at a faster rate

20
Q
A
21
Q

During exercise what happens to pulmonary vascular resistance? How can this be explained?

A

The pulmonary vascular resistance will decrease. This can be explained by the recruitment and distention of pulmonary capillaries that occurs in response to elevated blood flow and perfusion pressure.

22
Q

What role does recruitment play in reduction of pulmonary resistance?

A
  • As pressure increases:
    • Closed vessels may now open
    • Capillaries that were open but not conducting now begin to conduct blood

NOTE: The recruitment of additional parallel capillary pathways reduces overal vascular resistance

23
Q

What role does distention play in reduction of pulmonary resistance?

A
  • Once a vessel is open and conducting: furter pressure increases will increase transmural pressure
    • This causes the vessel to dilate
24
Q

How is derecruitment accomplished?

A
  • Low right ventricular output
  • High alveolar pressure

*This results in a decrease in surface area for gas exchange and may increase alveolar dead space

25
Q

Vasodilators

A
  • Increase in O2
  • Decrease in CO2
  • Increase in pH
  • Histamine, H2 agonists
  • Prostacyclin
  • Beta-adrenergic agonists
  • Bradykinin
  • Theophylline
  • Acetylcholine
  • NO
26
Q

Vasoconstrictors

A
  • Decrease in O2
  • Increase in CO2
  • Decrease in pH
  • Histamine, H1 agonists
  • Thromboxane A2, PGF2 aplha, PGE2
  • alpha-adrenergic agonists
  • Serotonin
  • Angiotensin II
27
Q

What factors are predisposing to pulmonary edema?

A
  • Increased capillary permeability
  • increased capillary hydrostatic pressure
  • Decreased interstitial hydrostatic pressure
  • Decreased colloid osmotic pressure
28
Q

What is the bronchial blood pressure in relation to systemic presure?

A

Equal

*This means that bronchial blood pressure is much higher than the pressure in pulmonary circulation

29
Q

The return of venous blood from the capillaries of the bronchial circulation to the heart occurs either through _________ veins or through_________ veins.

A

True bronchial; Bronchopulmonary

SF3- EXAM 2 (11 decks)

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