Ch 38 Pulmonary circulation, pleural fluid, and edema Flashcards
Where does the bronchial artery end?
The left atrium
What effect(s) does alveolar hypoxia have on pulmonary circulation?
Overall induces vasoconstriction by increasing release of or sensitivity to endothelin and other vasoconstrictors, and reduces release of Nitric Oxide (vasodilator)
In which regions of the lungs does zone 3 and zone 2 blood flow occur?
Lower areas = zone 3
Apices = zone 2
What effect does exercise have on pulmonary blood flow (changes in zones)
Pulmonary vascular pressure rises, converting zone 2 areas into zone 3 flow. The number of open capillaries increases, distending the capillaries and increasing the flow, and increasing pulmonary arterial pressure
How is negative pressure maintained in the pleural space?
Lymphatics pump fluid OUT of the pleural space
What causes edema of the pleural cavity?
-blocked lymphatic drainage
-cardiac failure
-reduced colloid osmotic pressure
-inflammation increasing permeability
How does the volume of the systemic circulation compare to that of the pulmonary system?
Systemic is 9x that of pulmonary
During systole, pressure in the pulmonary artery is equal to that of which chamber?
pressure in the right ventricle
What is meant by “zone 1 blood flow” and when does it occur?
Zone 1: when alveolar pressure > capillary pressure, collapsing the capillaries in that part of the lung
When: Severe blood loss enough to drop pulmonary systolic arterial pressure. Or when breathing against positive air pressure
What is meant by Zone 2 blood flow, and when might it occur?
Zone 2: Intermittent blood flow, occuring when pulmonary arterial pressure peaks, so that systolic pressure exceeds alveolar. BUT diastolic pressure < alveolar air pressure.
When: In the lung apices (dorsal most areas)
What is meant by Zone 3 blood flow, and when does it occur in the lungs?
Zone 3: Continuous blood flow. Arterial pressure and pulmonary capillary pressure remain above alveolar air pressures at all times.
When: In the dependent/lower areas of the lungs. Or during recumbency or intense exercise
How do the lungs accommodate extra blood flow during heavy exercise? (hint, 3 ways)
- Increased number of open capillaries
- Distending all the capillaries and increasing their rate of flow through each one (by > double)
- Increasing pulmonary arterial pressure
How does the lungs’ ability to accommodate increased blood flow preserve homeostasis? (2 ways)
- Conserves R side heart energy
- Prevents pulmonary edema by preventing significant rise in pulmonary capillary pressure
How does pulmonary capillary pressure compare to that of systemic caps?
Pulmonary is MUCH lower, by half at least
How does interstitial fluid pressure in the lungs compare to that in the peripheral tissues?
Interstitial fluid pressure is much more negative in the lungs
How does colloid osmotic pressure in the pulmonary capillaries compare to that of peripheral tissues?
Much higher, because the capillaries are more leaky to protein molecules
What are the implications of positive filtration pressure in the pulmonary capillaries, and how is this balanced?
Total outward forces > inward forces, so there is a slight continual flow of fluid from pulmonary caps into the interstitial spaces.
Some evaporates in alveoli, but most is pumped back into circulation through pulmonary lymphatics
How are the alveoli, under normal conditions, kept from filling with fluid?
Pulmonary lymphatics and capillaries maintain constant, slight negative pressure in the interstitium that sucks most fluid out and is carried off by lymphatics or capillaries
A rise in pulmonary interstitial fluid pressure into the positive range will result in _______
pulmonary edema
Complete the statement:
Pulmonary capillary pressure must rise to at least the value equal to _________ pressure before significant pulmonary edema develops
the colloid osmotic pressure of plasma within the capillaries
How does the lymphatics system guard against chronically elevated pulmonary capillary pressure?
lymph vessels expand to carry away excess fluid. Acute changes can be rapidly lethal however
Where do pulmonary lymphatic vessels open into?
mediastinum, superior surface of the diaphragm, and the lateral surfaces of the parietal pleura
