Blood Flow and Metabolism in the Pulmonary Circulatio Flashcards
Gas exchange occurs between the
alveolar air and the pulmonary capillaries.
- Pulmonary Perfusion
Deoxygenated blood (venous blood) circulates throughout the lung vasculature (pulmonary
capillaries) to be oxygenated
PULMONARY PRESSURE CIRCULATION
low-pressure circulation (2;25 mm Hg
Perfusion Pressure for Pulmonary Circulation
Pressure difference
between pulmonary artery (mean) and left atrium
Perfusion Pressure for Systemic Circulation
Pressure difference
between systemic artery (mean) and right atrium (100-2= 98 mmHg)
t/f Pressure around pulmonary vessels is less than alveolar pressure
true
t/f pulmonary Vessels increase their caliber as lung expands
true
alveolar pressure is closer to
atmospheric pressure
when alveolar pressure rises above capillary pressure
capillaries collapse
pulmonary vascular resistance is calculated
(input pressure - output pressure) / blood flow
t/f in the lungs, there are no muscular arterioles
true
pulmonary resistance
1.7 mm Hg/L/min
Systemic Resistance
17 mm Hg/L/min
mean pressure in the pulmonary artery
15 mmhg
Recruitment:
Opening closed capillaries at higher pressures
Distension
Widening of capillaries as pressure rises
As pressures rise
these vessels begin to
conduct blood, which lowers the
resistance.
main mechanism responsible for the decrease in vascular resistance
pulmonary artery pressure increase
blood flow is measured to
Assess lung function in respiratory
distress
blood flow can be measured from
ratio of oxygen consumed over oxygen
concentration differences in arteries and veins
Frick law is used to calculate
blood flow
what is the dynamic of blood flow in lungs?
More flow at base, less at apex
Pulmonary arterial system: a continuous column of blood
Pressure difference between top and bottom is about 23 mm Hg
zone 1 in the lung
No flow (artery < alveolar pressure, rare in health)
alveolar pressure is higher than pulmonary artery pressure
capillaries are flatenned
Zone 2 in the lung
Flow = artery-alveolar pressure (waterfall effect)
Pulmonary arterial pressure is higher than alveolar pressure
venous pressure lower than alveolar
Arterial pressure increases down the lung, but alveolar pressure remains the same , pressure difference responsible for blood flow also increses
zone 3 in lung
arteriolar - vein pressure (normal).
venous pressure higher than alveolar pressure
increase in blood flow in this region of the lung is due to distension of capillaries and pressure within them increase
recruitment is also involved
If there is a severe hemorrhage, what happens to arterial blood pressure in zone 1 ?
it is reduced
if alveolar pressure is raised in zone 1, what happens?
hyperventilation
If the lung is well ventilated but un-perfused
No gas exchange occurs, is referred to alveolar dead space
blood flow is determined by the pressure difference between
arterial and alveolar, and venous pressure has no effect.
The random arrangement of blood vessels and capillaries cause
inequality of blood flow at all levels of the lung.
t/f Blood flow increases along the acinus
true
in active control of circulation, blood flow is directed away from
Poorly ventilated areas of the lung
Under normal conditions, passive factors dictate.
pulmonary vascular resistance and distribution of blood flow
When O2 in alveolar gas drops
Active response is initiated, and small arterioles in the hypoxic region of the lung will constrict
Hypoxic pulmonary vasoconstriction
occurs without input from the CNS
determined by alveolar gas, NOT BY PULMONARY ATERIAL BLOOD
Pulmonary arterial pressure increases
Pulmonary vascular resistance is associated with
Hypoxic conditions vasoconstriciton
During the fetal stage, pulmonary vascular resistance is high due to
hypoxic vasoconstriction
Hypoxic pulmonary vasoconstriction will direct blood
away from hypoxic areas
Starling’s law: fluid movement is important
keep lungs dry, slight outward flow of water to lymph drainage
When Water Balance Fails
- Interstitial edema: Fluid in perivascular spaces.
- Alveolar edema: Fluid in alveoli → poor gas exchange.
pulmonary circulation also works for
blood reservoir
filtering-removing small thrombi to prevent reaching the brain , trapping white blood cells
metabolic functions of lungs
Modifies vasoactive substances (e.g., angiotensin, serotonin).
* Many vasoactive and bronchoactive substances are metabolized in the lung and released under certain conditions
t/f the lungs receive all cardiac output
true
angiotensin 1 is transformed to
II (via ACE, vasoconstrictor).
Bradykinin is
inactivated
Serotonin is
removed
Alveolar edema impairs
gas exchange
