Pulmonary Circulation Flashcards
What is the pathway of the high pressure, low flow circulation?
Thoracic aorta -> bronchial arteries
Trachea, bronchial tree, adventitia, CT
What is the pathway of the low pressure, high flow?
Pulmonary artery and branches -> alveoli
The wall thickness of the arterial artery is ___ that of the aorta.
1/3
The wall thickness of the arterial artery is 1/3 that of the aorta. What effect does this have on compliance?
The pulmonary arterial tree has a larger compliance.
What is the pulmonary arterial pressure?
24/9 mm Hg
What is the mean pulmonary arterial pressure?
15 mm Hg
What is the left atrium pressure?
8 mm Hg
What are agents that constrict pulmonary arterioles?
Norepinephrine
Epinephrine
Angiotensin II
Some prostraglandins
What are some agents that dilate pulmonary arterioles?
isoproterenol
Acetylcholine
What are some agents that constrict pulmonary venules?
Serotonin
Histamine
E. coli endotoxin
What do sympathetic vasoconstrictor nerve fibers affect blood outflow?
They decrease pulmonary blood flow by 30%. This mobilizes blood from pulmonary nerves.
What effect does heavy exercise have on blood flow through the lungs and why does this cause minimal rise in pulomnary arterial pressure?
It increases blood flow through lungs by 4 - 7 times.
A minimal rise occurs because the number of capillaries opens up, and they are also distended (increases flow rate up to 2 times).
How does failure of the left side of the heart affect pulmonary circulation?
Pressure builds up greatly.
What zone of the lung has no blood flow?
Zone 1
In this zone, local alveolar capillary pressure never rises higher than alveolar air pressure.
In which zone is there intermittent blood flow only during systole?
Zone 2
In which zone is there continuuous blood flow?
Zone 3
The apices of the lung has what type of flow?
Zone 2 flow (intermittent flow during systole)
Lower areas of the lungs have what type of flow?
Zone 3 flow
You have completed heavy exercise. How does the blood flow change through the lungs?
Blood flow in the apices is converted from zone 2 to zone 3 flow.
Describe the hydrostatic and osmotic forces involved in lung capillary fluid exchange.
Hydrostatic and osmotic forces produce a mean filtration pressure of 1 mm Hg (29 - 28).
Colloid osmotic pressure in pulmonary interstitial tissue is about 14 mm Hg compared to less than 7 mm Hg in peripheral tissues.
What are the most common causes of pulmonary edema?
Left-sided heart failure
Mitral valvue disease
Damage to pulmonary blood capillary membranes:
infections
breathing noxious substances.
At what capillary pressure does a pulmonary edema occur?
Occurs when pulmonary capillary pressure > 25 mm Hg
What might happen when capillary pressure remains chronically elevated for two weeks or more?
Compensation usually occurs by an increase in the lymphatic system, which carries excess fluid away.
What are the causes of pleural effusion?
Blockage of lymphatic drainange from pleural cavity
cardiac failure
reduced plasma colloid osmotic pressure
Infection/inflammation
If the pressure in the pleural space becomes positive, what happens to the lungs?
They tend to collapse
Hypoxia increases pressure in the pulmonary artery. How does it cause increaesd pressure?
by the release of prostanglandins.
What are the reults of bronchial obstruction and hypoxia in relation to blood flow?
Bronchial obstruction causes constriction of vessels. This is due to locally due to low alveolar PO2 effects on the vessels.
During bronchial obstruction, what occurs to the pH?
It decreases.
This causes vasoconstriction in pulmonary vessels and vasoDILATION in other tissues.
How does bronchial obstruction affect blood flow?
It is reduced in a portion of the lung. Alveolar PCO2 is lowered, resulting a constriction of the bronchi supplying that portion of the lung.
What are the two circulations of the lung?
High pressure, low flow
Low pressure, high flow
