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Phys2 Pulm circulat

QuestionAnswer
What is role of the Pulmonary circulation? transport deoxy BL to the lungs and oxygenated BL from the lungs to the heart.
How much BL is pumped through the pulmonary artery per beat? 5 L/min (same as CO)
Pathway through pulomnary circulation 1.Pulmonary arteries (carry deoxy BL from RV and branch as the airways branch). 2.Branches following the airways. 3.Mesh of capillary at the respiratory bronchioles & alveoli. 4.Pulmonary venules (drains oxygenated BL from capillaries). 5.Pulmonary Ve
Is pulmonary circulation a high pressure sytem? NO, LOW pressure and HIGH flow. Mean pressure is 15mmHg in the pulmonary artery. **this decreases the amount of work required of the RV
Is there a lot of smooth muscle in the Pulmonary arteries? NO, there is no need to direct or adjust BF, therefore not a lot of smooth muscle.
Internal capillary pressure > Alveolar pressure capillary becomes DISTENDED.
Alveolar pressure > Internal capillary pressure capillary becomes COMPRESSED.
What are "Extra"-Alveolar vessels? Pulmonary arteries and veins. **those vessels not in direct contact/exposure to alveolar pressure.
Does radial traction affect extra-alveolar vessels? YES, in the same way it does airways. **It will Inc the diameter of the vessels.
Diameter (caliber) of Alveolar vessels is determined by? extra-alveolar vessels? Alveolar: Balance b/w internal and Alveolar pressure. Extra: Lung vol (Inc vol = Inc radial traction = Inc diameter)
Pulmonary Vascular Resistance (PVR) 1/10th systemic vascular resistance. R = (Ppulmartery-Pla)/Q
Calculate PVR if pulmonary arterial pressure is 15mmHg and the left atrial pressure is 5mmHg at 5L/min 2mmHg.sec/L
How does PVR respond to increased arterial or venous pressure? DECREASES **Also decreases with Inc CO but INCREASES with dec CO.
Mechanism behind Decreased PVR When arterial pressure and CO are increased, the PVR is reduced by: 1.Recruiting or opening more pulmonary capillaries (since not all are open at rest). 2.Distending or widening pulmonary capillaries
PVR response to High Lung Volume (TLC)? INCREASES. the extra-alveolar vessels are stretched open by radial traction, but the high alveolar volume also stretches the pulmonary capillaries. This also narrows them, increasing their resistance and the overall pulmonary vascular resistance
PVR response to Low Lung Volume (RV)? INCREASES. Even though there is lowered Alveolar pressure, there is NO radial traction on the vessels to increase their diameter and decrease resistance.
Why is PVR the lowest at FRC (intrapleural pressure of -5cm H2O)? B/c there is enough radial traction to hold open the extra-alveolar vessels and minimal alveolar pressure to stretch the capillaries.
Is BF uniform in the upright lung? NO. It increases linearly from Apex to BASE. **Apical BF can be close to 0
What explains the variation in lung BF? Balance in hydrostatic pressure in the lung
What happens to arterial pressure as you go up the lung from the base to the apex? DECREASES!
Zone 1 of BF in the lungs Upper 1/3 of lung. PA (alveolar pressure) is greater than the Pa (arterial pressure) which causes the capillaries to collapse. **BF isn't possible.
Zone 2 of BF in the lungs Middle 1/3 of lung. Pa is slightly higher than PA so come capillaries are open. **Alveolar pressure is greater than venous pressure so the difference b/w it and Pa determines BF.
Zone 3 of BF in the lungs Lower 1/3 of lungs. Arterial and venous pressures are highest and both are > than PA. Distention of the capillaries occurs. **A-V pressure difference thus controls BF.
Hypoxic pulmonary vasoconstriction As alveolar PO2 (not arterial or venous PO2) decreases, the BF decreases. **closes O2-sensitive K+ channels which leads to depolarization and smooth muscle vasoconstriction.
Why is hypoxic pulmonary vasoconsrtiction a useful response? b/c is re-directs BF AWAY from UNDER-ventilated areas (minimizes potential hypoxemia).
When is hypoxic pulmonary vasoconstriction disadvantageous? Why hypoxia is generalized across the entire lung. (Seen with high altitudes). **Causes pulmonary HTN and edema (HAPE) and leads to HF. Also seen in COPD patients
Why is excess fluid in the lungs (pneumonia and edema) disadvantageous? Increases the diffusion pathway and increases surface tension, thus reducing compliance. **MUST keep alveoli DRY
Net fluid leakage: Forces pulling fluid out of capillaries into the lungs 1.CHP. 2.Inc Surface Tension
Net fluid leakage: Forces keeping fluid in the capillary lumen 1.COP. 2.Inc Alveolar Pressure (pushes fluid back into capillary).
How is fluid that leaks from the capillaries into the interstium removed? Drains through lymphatic channels in the perivascular spaces. **If blocked, fluid will back up into alveoli.
What will happen during early stage edema? Engorgement of interstitial spaces b/c fluid is leaving the capillaries due to Inc CHP and entering the interstitium.
What will happen during late stage edema? The lymph channels will become backed up and fluid will enter into the alveoli.
Created by: WeeG
 

 



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