Circulation Flashcards
Describe pulmonary circulation
How are the pulmonary and systemic circulations connected?
In series
Pulmonary arteries carry…
Pulmonary veins carry…
How far do the pulmonary arteries “travel” with the airways?
They travel as far as the terminal bronchioles.
Where do pulmonary capillaries form a dense network?
In the alveolar septa (walls)
What is the function of bronchial arteries?
Supply bronchial tissues with nutrients and oxygen to support their function. Contribute to warming of the air flowing through the bronchi.
The pulmonary and system circulations carry the same… at any one time.
flow (cardiac output)
How do arterial walls of the pulmonary arteries compare to those of the systemic arteries?
They are much thinner, less muscular, so their diameter changes in response to surrounding pressures; pulmonary arterial pressures are relatively low.
What is resistance?
Impedance to flow, the “energy cost” for flow
What is the pulmonary vascular resistance? (PVR)
“Energy cost” for flow in the pulmonary vasculature from the pulmonary artery to the left atrium.
How do the walls of the right ventricle compare to those of the left ventricle of the heart? Why?
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.
How does the resistance of the pulmonary circulation compare to that of the systemic circulation?
The resistance in the pulmonary circulation system is much lower.
What determines the PVR?
cardiac output
What is the transmural pressure?
Pressure difference between the inside and outside of a vessel
What is the transmural pressure like in the pulmonary vasculature? How does it compare to the systemic vasculature?
In a rigid tube, increasing the driving pressure results in…
proportional increase in flow rate (linear relationship)
In more compliant/flexible/elastic tubes, increasing the driving pressure results in…
mechanism lungs useed to keep pressures low…
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
Increases in flow change the mechanics of the pulmonary vasculature through two mechanisms:
- vascular distension (increased diameter of open vessels_
-vascular recruitment (opening of previously closed vessels)
How do alveolar vessels change with increasing lung volume? How do extra-alveolar vessels change?
What is the net result at high lung volume?
Alveolar vessels get smaller (higher resistance)
Extra-alveolar vessels get larger (lower resistance)
Net result:
Pulmonary blood flow varies by the … of the lung. It generally follows …
Pulmonary blood flow varies by region of the lung, generally follows gravity.
What are he pressures that influence regional blood flow?
PA: pulmonary alveola
Pa: pulmonary arterial pressure
Pv: Pulmonary venous pressure
What are the 3 physiologic zones in the lungs that are useful to think about when understanding regional flow?
Zone I: top of the lung
Zone II: middle of the lung
Zone III: bottom of the lung
How do PA, Pa, Pv compare to one another in Zone I?
PA>Pa>Pv
How do PA, Pa, Pv compare to one another in Zone II?
Pa>PA>Pv
How do PA, Pa, Pv compare to one another in Zone III?
Pa>Pv>PA
Describe Zone I circulation
?
Describe Zone II circulation
Arterial pressure is higher because it doesn’t have to push against cavity as much as it does at the top of the lung.
Describe Zone III circulation
What determines flow in Zone II?
Difference between Pa and Palv
What is the purpose of pulmonary vasoconstriction?
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.
What is the clinical use of pulmonary vasodilation?
Decreased pulmonary vascular resistance achieved by inhalation of nitric oxide (NO) (NO causes smooth muscle relaxation).
In order for gas exchange to occur, it is essential that the alveolar surface be kept…
dry
(?? why? what about surfactant)
Define flux
What are the Starling forces?
Hydrostatic pressure and oncotic pressure
Describe the net fluid flux in the lung.
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 (??)
What happens when the capacity of the lymphatics to drain the fluid moving into the intersitial space of the lungs is exceed?
Edema
What is the difference between interstitial pulmonary edema and alveolar pulmonary edema?
What is a pleural effusion?
