Pulmonary Circulation

Question 1

compare the relative levels of O2 and CO2 in the arterial and venous sides of the pulmonary, systemic, and bronchial circuits

Answer 1

pulmonary:
arterial: deoxygenated
venous: oxygenated

systemic:
arterial: oxygenated
venous: deoxygenated

bronchial:
arterial: oxygenated (bronchial artery branches from aorta)
venous: deoxygenated (merges with pulmonary venules and eventually pulmonary vein, azygous veins)

Question 2

compare flow, pressure, resistance, and response to hypoxemia in the pulmonary vascular circuit versus the systemic vascular circuit

Answer 2

if systemic circulation experiences hypoxemia, will cause vasodilation to decrease systemic vascular resistance to cause more blood flow to hypoxic systemic tissues for more blood delivering more oxygen

if pulmonary circulation experiences hypoxemia, will respond with vasoconstriction, increasing systemic vascular resistance and decreasing blood flow so the alveoli have more time for gas exchange with the slower flow

Question 3

describe where the bronchial circulation can enter and leave both pulmonary and systemic circuits

Answer 3

bronchial artery branches off the aorta to supply the bronchial walls, visceral pleura, and large vessel walls with oxygenated blood

bronchiole post-capillary venules (deoxygenated) merge with pulmonary venules (oxygenated) and pulmonary veins, and also azygous veins to go back to left atrium

Question 4

describe how starling’s forces impact the movement of fluid between the pulmonary capillaries, the interstitial space, and the alveolar lumen; compare the relative differences in these forces to those in systemic vasculature

Answer 4

pulmonary pressures are low due to:
1. the pulmonary arterioles being thin-walled, having less smooth muscle than systemic, and less basal tone
2. pulmonary venules being wider than systemic venules
3. all of this allowing pulmonary vessels to expand to accomodate a large volume of blood

IF arterial pressures were high, there would be increased hydrostatic pressure which would cause fluid to exit small vessels into interstitium and then alveoli, which would overwhelm the pump that removes fluid from alveoli, leading to pulmonary edema

Question 5

describe the effects of inspiration and expiration on blood flow in pulmonary capillaries and extra-alveolar vessels (arterioles and veins) in the lungs

Answer 5

effect of inspiration:
1. thoracic cavity expands
2. extra-alveolar vessels expand, reducing vascular resistance
3. intra-alveolar vessels are compressed, increasing vascular resistance

effect of expiration:
1. thoracic cavity is compressed
2. extra-alveolar vessels are compressed, increasing vascular resistance
3. intra-alveolar vessels expand, decreasing vascular resistance

Question 6

describe the mechanism by which the pulmonary vasculature accommodates increased cardiac output