Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
17 Cards in this Set
- Front
- Back
|
Function of thebesian vein.
|
Drains coronary venous blood directly into LV (rather than to lungs via PA)
|
|
|
Pulmonary vs Systemic Circulation:
Blood Flow Pressure Resistance |
Blood flow the same (=cardiac output)
Pulm circulation has lower pressures and resistances |
|
|
Which lung arteries exhibit high pressure? Why?
|
Bronchial arteries exhibit high pressure bc directly originate from systemic circulation (aorta)
|
|
|
Pulmonary lymphatics drain via the _____.
|
Thoracic duct
|
|
|
What is hypoxic vasoconstriction? Describe its mechanism of action.
|
Decreases in PAO2 produce pulmonary vasoconstriction, which reduces pulm blood flow to poorly ventilated regions and toward well-ventilated regions.
When PAO2 drops below 70mmHg, vasc SM cells sense hypoxia, vasoconstrict, and reduce blood flow in that region. |
|
|
What role does NO synthase play in hypoxic vasoconstriction?
|
Inhibition of NO synthase enhances hypoxic vasoconstriction (inhaled NO reduces hypoxic vasoconstriction)
|
|
|
What is the effect of acute high altitudes on vasoconstriction?
Chronic high altitude? |
Acute high altitude reduces PAO2 throughout lungs, producing global pulmonary vasoconstriction and increased vascular resistance. PA pressure increases.
If chronic-->RV hypertrophy |
|
|
When is global hypoxic vasoconstriction considered a normal state?
|
In fetal circulation
|
|
|
Which arachidonic acid metabolites induce vasoconstriction?
Vasodilation? |
Thomboxane A2, Leukotrienes-->Constrict
Prostacyclin-->vasodilate |
|
|
List the zones of the lung (1-3) in relation to apex/base.
Where is V/Q the highest? |
Zone 1 = apex
Zone 3 = base Although ventilation and perfusion are greater in gravity-dependent regions, this is more for perfusion than ventilation. V/Q is higher in apical regions. |
|
|
Zones 1-3:
Pressure gradients driving blood flow |
Zone 1: PA≥Pa>Pv
Zone 2: Pa>PA>Pv; blood flow driven by arterial and alveolar difference Zone 3: Pa>Pv>PA: blood flow driven by diff b/t arterial and venous pressure. Greatest number of capillaries open. |
|
|
Under what circumstances would alveoli in Zone 1 collapse?
|
Remember, in Zone 1: PA≥Pa>Pv
When Pa lower than PA, pulm capillaries compressed by higher alveolar pressure and capillaries close (Reducing blood flow). Normally, arterial pressure just high enough to prevent closure. If arterial pressure decreased, such as in HEMORRHAGE, or if alveolar pressure is increased, such as in POSITIVE PRESSURE BREATHING (mechanical ventilation), blood vessels will close. |
|
|
When do right-to-left shunts occur?
Effects? Defining characteristic? |
Occur with septal defects.
Hypoxemia ALWAYS results because significant fraction of cardiac output not delivered to lungs for oxygenation. The blood that does make it to lungs for oxygenation is then 'diluted' by low O2 shunted blood. Defining characteristic: Can't be corrected by having person breathe 100% oxygen. Wouldn't see inc in PaCO2 bc central chemoreceptors would respond. |
|
|
When do left-to-right shunts occur?
Effects? |
More common, don't cause hypoxemia.
Due to patent ductus arteriosus, trauma. Oxygenated blood retruning from lungs added to right heart w/o systemic delivery. PO2 in blood in right heart will be elevated. |
|
|
What is a V/Q mismatch?
|
Abnormal gas exchange that may be due to ventilation of lung regions that aren't perfused (dead space) or perfusion of lungs that aren't ventilated (shunts).
|
|
|
Dead Space:
V/Q value Clinical example PAO2, PACO2 values |
Dead Space: ventilation of lung regions that aren't perfused. Ventilation wasted.
V/Q = ∞ Ex: pulmonary embolism PAO2: 150 mmHg PACO2: 0 |
|
|
Shunt:
V/Q value Clinical example PAO2, PACO2 values |
Shunt: perfusino of lung regions that aren't ventilated.
Ex: airway obstruction, right-to-left cardiac shunts bc no gas exchange occurs, has same composition as mixed venous blood: PAO2=40, PACO2=46 |
