Circulation

Question 1

Describe pulmonary circulation

Question 2

How are the pulmonary and systemic circulations connected?

Answer 2

In series

Question 3

Pulmonary arteries carry…
Pulmonary veins carry…

Question 4

How far do the pulmonary arteries “travel” with the airways?

Answer 4

They travel as far as the terminal bronchioles.

Question 5

Where do pulmonary capillaries form a dense network?

Answer 5

In the alveolar septa (walls)

Question 6

What is the function of bronchial arteries?

Answer 6

Supply bronchial tissues with nutrients and oxygen to support their function. Contribute to warming of the air flowing through the bronchi.

Question 7

The pulmonary and system circulations carry the same… at any one time.

Answer 7

flow (cardiac output)

Question 8

How do arterial walls of the pulmonary arteries compare to those of the systemic arteries?

Answer 8

They are much thinner, less muscular, so their diameter changes in response to surrounding pressures; pulmonary arterial pressures are relatively low.

Question 9

What is resistance?

Answer 9

Impedance to flow, the “energy cost” for flow

Question 10

What is the pulmonary vascular resistance? (PVR)

Answer 10

“Energy cost” for flow in the pulmonary vasculature from the pulmonary artery to the left atrium.

Question 11

How do the walls of the right ventricle compare to those of the left ventricle of the heart? Why?

Answer 11

The walls of the right ventricle are less muscular than those of the left ventricle because the pulmonary circulation is a relatively low pressure system.

Question 12

How does the resistance of the pulmonary circulation compare to that of the systemic circulation?

Answer 12

The resistance in the pulmonary circulation system is much lower.

Question 13

What determines the PVR?

Answer 13

cardiac output

Question 14

What is the transmural pressure?

Answer 14

Pressure difference between the inside and outside of a vessel

Question 15

What is the transmural pressure like in the pulmonary vasculature? How does it compare to the systemic vasculature?

Question 16

In a rigid tube, increasing the driving pressure results in…

Answer 16

proportional increase in flow rate (linear relationship)

Question 17

In more compliant/flexible/elastic tubes, increasing the driving pressure results in…
mechanism lungs useed to keep pressures low…

Answer 17

small flow rate increase (you need a lot more pressure to increase the flow rate) - as you increase flow, the resistance is going down???? huh this made no sense

Question 18

Increases in flow change the mechanics of the pulmonary vasculature through two mechanisms:

Answer 18

• vascular distension (increased diameter of open vessels_
  -vascular recruitment (opening of previously closed vessels)

Question 19

How do alveolar vessels change with increasing lung volume? How do extra-alveolar vessels change?
What is the net result at high lung volume?

Answer 19

Alveolar vessels get smaller (higher resistance)
Extra-alveolar vessels get larger (lower resistance)
Net result:

Question 20

Pulmonary blood flow varies by the … of the lung. It generally follows …

Answer 20

Pulmonary blood flow varies by region of the lung, generally follows gravity.

Question 21

What are he pressures that influence regional blood flow?

Answer 21

PA: pulmonary alveola
Pa: pulmonary arterial pressure
Pv: Pulmonary venous pressure

Question 22

What are the 3 physiologic zones in the lungs that are useful to think about when understanding regional flow?

Answer 22

Zone I: top of the lung

Zone II: middle of the lung

Zone III: bottom of the lung

Question 23

How do PA, Pa, Pv compare to one another in Zone I?

Answer 23

PA>Pa>Pv

Question 24

How do PA, Pa, Pv compare to one another in Zone II?

Answer 24

Pa>PA>Pv

Question 25

How do PA, Pa, Pv compare to one another in Zone III?

Answer 25

Pa>Pv>PA

Question 26

Describe Zone I circulation

Answer 26

?

Question 27

Describe Zone II circulation

Answer 27

Arterial pressure is higher because it doesn’t have to push against cavity as much as it does at the top of the lung.

Question 28

Describe Zone III circulation

Question 29

What determines flow in Zone II?

Answer 29

Difference between Pa and Palv

Question 30

What is the purpose of pulmonary vasoconstriction?

Answer 30

It is a chemical reflex that will constrict vessels in areas where gas exchange is poor (in areas of hypoxia) to try to limit wasted blood flow to that area.

Question 31

What is the clinical use of pulmonary vasodilation?

Answer 31

Decreased pulmonary vascular resistance achieved by inhalation of nitric oxide (NO) (NO causes smooth muscle relaxation).

Question 32

In order for gas exchange to occur, it is essential that the alveolar surface be kept…

Answer 32

dry
(?? why? what about surfactant)

Question 33

Define flux

Question 34

What are the Starling forces?

Answer 34

Hydrostatic pressure and oncotic pressure

Question 35

Describe the net fluid flux in the lung.

Answer 35

There is a very small gradient of pressure moving fluid out of the blood into the interstitial space and onto the alveolar lining. In order to prevent a wet alveolar” surface, this fluid is drained via the lymphatic system (??)

Question 36

What happens when the capacity of the lymphatics to drain the fluid moving into the intersitial space of the lungs is exceed?

Answer 36

Edema

Question 37

What is the difference between interstitial pulmonary edema and alveolar pulmonary edema?

Question 38

What is a pleural effusion?