HK 3810 Package 3 Respiration.docx

Bronchial circulation o part of the systemic

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Bronchial circulation o Part of the systemic circulation o Supplies pulmonary structures with nutrients and removes waste o Feeds everything in pulmonary system except the alveoli (the pulmonary capillary bed does this) Pulmonary circulation o From right ventricle through pulmonary artery (low O2, high CO2) by alveoli (close to atmospheric air) through pulmonary vein (high O2, low CO2) to left atria left ventricle through aort to systemic circulation o Q = P1 – P2/R o CO right heart = mean pulmonary artery pressure – LAP / total pulmonary resistance Regulation of vasculature radius Change in smooth muscle function o Neural – some SNS innervation Both veins and arteries Little power here Cause vasoconstriction (stiffens wall, but no change in r) Some PNS innervation o Endocrine – alpha (vasoconstriction) and beta (vasodilation) adrenergic Rm population Circulating epi/NE will have very little effect on r bc both alpha and beta are present o Paracrine – endothelial cells Endothelin and prostaglandin are vasoconstrictors NO and prostacyclins are vasodilators o Local control – controlled by what is in the alveoli O2 increase PAO2 increase O2 in alveolus vasodilation Everywhere else, O2 is a vasoconstrictor Decrease PAO2 decrease O2 in alveolus vasoconstriction Transmural pressure o Extra alveolar vessels – arteries, arterioles, veins not directly associated with the alveoli At rest pressure is -4cmH2O When we inspire, pressure is -8cmH2O; increase in r, decrease in R, increase in Q When we expire, decrease in r, increase in R, decrease in Q o Alveolar vessels – capillaries directly associated with the alveoli Transmural pressure = pressure in alveolus (PA) If PA > PpulmA > PpulmV no Q If PpulmA >PA > PpulmV reduced, intermittent Q If PpulmA > PpulmV > PA continuous Q o Gravity – sitting/standing There is a pressure gradient for Q across the lung of 8mmHg
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HK 3810 Package 3 Respiration Bottom of the lung has Ppulma = 34mmHg, Ppulmv = 26mmHg Middle has Ppulma = 19mmHg, PpulmV = 11mmHg High pressure at the bottom of the lung will increase r of blood vessels at the bottom decrease R, increase Q This is due to the elastic nature of the vasculature in pulmonary system increase Q at bottom of lung Due to an uneven distribution of pressure across the lung PA > PpulmA > PpulmV no Q PpulmA >PA > PpulmV reduced, intermittent Q If PpulmA > PpulmV > PA continuous Q VA/Q There is greater blood flow at the bottom of the lung than at the top There is greater ventilation at the bottom of thelung They are not matched across the whole lung, except for one spot At this spot (3 rd rib), VA/Q = 1, but as you move to the bottom of the lung there is an increase in VA and an even greater increase in Q so the ration drops because there is more Q than VA At the top of the lung, there is a decrease in VA and an even greater decrease in Q, so there is an increase in ratio because Q is less than VA Optimal ratio is needed for exchange of gases (O2, Co2, N2) between air in blood When there is no VA
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  • Fall '16
  • Coral Murrant
  • pulmonary artery

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