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33 Cards in this Set
- Front
- Back
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What is the surface area of the pulmonary capillaries?
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100 m^2
(40x the body surface area) |
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How does pulmonary circulation differ from the systemic one?
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1) BP in pulmonary circulation is less thn BP in systemic circulation
2) Walls of the pulmonary capillaries are thinner than similar vessels in systemic circulation 3) RV: P of ~25 mmHg for pulmonary circulation LV: P of ~120 mm Hg for systemic circulation |
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What are the P of the pulmonary and systemic circulations?
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RA: 3
RV: 25/0 LA: 5 LV:120/0 Systemic artery: 120/80 (mean of 100) goes to RA Pulmonary artery: 25/8 (mean of 15) goes to LA |
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Which ventricle creates more P?
Wy? |
LV
Left side of the heart needs to pump with more power than the right side because it has to send blood all over the body Right side only needs to send blood to the lungs |
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What does blood flow depend on?
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Vascular pressure and resistance
Flow= Pressure/Resistance |
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What is the drop in blood P from the pulmonary artery to the LA?
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10mm Hg
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What is the drop in blood P from systemic artery to RA?
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100mm Hg
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How does pulmonary resistance compare to systemic resistance?
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Pulmonary resistance is 1/10 of systemic circulation resistance
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Why does pulmonary circulation have such low resistance?
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Thin walls of vascular system
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How can the pulmonary and systemic circulations have the same flow?
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The pressure in pulmonary circulation is also 10X smaller than systemic
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What happens when the alveolarP increases above the P in the capillaries?
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The pulmonary caps collapse
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What happens at large lung volumes and increased alveolar P?
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The pulmonary capillaries collapse
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How does lung volume affect largere vessels (arteries/veins)?
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They increase their caliber as the lungs expand
They're pullled open by the radial traction of the surrounding lung parenchyma Thesevessels are exposed to INTRAPLEURAL P, not alveolar P **Pulmonary flow is .: affected by lung volume** |
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What happens to the extra-alveolar vessels?
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They're exposed to intrapleural P, not alveolar P, so they don't get compressed
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What happens as pulmonary flow increases?
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Pulmonary resistance decreases
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What capacity for accomadation does the pulmonary ciculation have?
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Can accomadate 2- to 3-fold increases in caridac output with little change in pulmonary arterial P
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Why does resistance decrease when pulmonary flow increases?
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Increase of cross sectional area of the vascular bed
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What is distension and recruitment in accomadation?
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Distension: Blood vessels already open may increase their caliber (open even more)
Recruitment: Previously closed vessels may open as the cardiac output rises |
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What affect do drugs like serotonin, histamine and norepineprhine have on pulmonary vascular resistance?
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Cause contraction of smooth muscle
->Increase pulmonary vascular resistance in larger pulmonary arteries |
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What affect do drugs like acetylcholine and isoproterabol have on pulmonary vascular resistance?
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Relax smooth muscle
-> Decrease pulmonary vascular resistance |
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What does nitric oxide do?
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Produce by endothelial cells
Relaxes smooth muscle Leads to vasodilation |
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Where does reflex vasoconstriction take place?
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In regions of the lungs that are poorly oxygenated
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How does gravity affect pulmonary blood flow?
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Depends on body posture
->Upright position: blood flow increases linearly from top to bottom of the lungs |
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Why are vessels at the bottm of the lungs more distended?
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Gravity increases vascular pressure
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What happens at the top of the lungs if alveolar P is greater than blood P in the capillaries?
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The pulmonary capillaries can be completely compressed
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Where does more blood flow in the lungs?
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At the bottom,because of gravity
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What was used tto measure the distribtuion of blood in the body?
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Radioactive xenon
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What happens to the alveoli of the lungs at rest?
During breathing? |
At rest: alveoli at the top of the lungs are more opened
Breathing:alveoli at the bottom of the lungs are opned wider -> Preferential ventilation of the bottom of the lungs ->Bottom alveoli will change volume more than the top ones |
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What is the ventilation/perfusion (blood flow) ratio in the lungs?
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Ventilation/perfusion (blood flow= perfusion) ratio is abnormally high at the top and much lower at the bottom of the lungs
Because ventilation increases slowly from top to bottom and blood flow increases rapidly from the top to the bottom of the lungs |
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What is VO2?
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O2 consumption per minute = to the O2 taken up by the blood in the lungs in one minute
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What happens to vascular resisance above/below FRC? at FRC?
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Above/below: Vascular R increases
At FRC: Vascular R decreases |
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Why does resistance increase above FRC?
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Alveolar vessels are sretched longitudinally
diameter decrease so there is an increase in vascular resistance |
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What happens below FRC?
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extra-alveolar vessels collapse because they aren't stretched by the pulmonary tissues
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