= Blood Supply + Gas Exchange + Lung Pathologies Affecting Diffusion Flashcards
What does the bronchial circulation supply ?
Supplies oxygenated blood via bronchial arteries arising from systemic circulation to lung tissues
What % does bronchial circulation comprise of left heart output ?
2%
What vessel drains blood to left atrium ?
Pulmonary vein
What does the pulmonary circulation consist of ?
L and R pulmonary arteries
Where do the left and right pulmonary arteries arise from ?
Right ventricle
What does the left and right pulmonary arteries carry ?
Entire cardiac output from RV
What does the pulmonary artery supply ?
Dense capillary network surrounding the alveoli
Where does the blood return to after supplying the capillary network surrounding alveoli ?
Oxygenated blood is returned to left atrium via pulmonary vein
How is the pulmonary circulation described ?
High flow, low pressure system (25/10mmHg)
What is the partial pressure of O2 in alveoli ?
100mmHg (13.3kPa)
What is the partial pressure of CO2 in alveoli ?
40mmHg (5.3kPa)
What do partial pressures in the systemic venous blood reflect ?
What’s happening in our peripheral tissues
What do partial pressures in systemic arterial blood reflect ?
What’s happening in our alveoli
What does A stand for ?
Alveolar
What does a stand for ?
Arterial blood
What does ṽ stand for ?
Mixed venous blood (e.g. pulmonary artery)
What are the values of PAO2 and PACO2 ?
Alveolar PO2- 100mmHg (13.3kPa)Alveolar PCO2- 40mmHg (5.3kPa)
What are the values of PaO2 and PaCO2 ?
Arterial PO2- 100mmHg (13.3kPa)Arterial PCO2- 40mmHg (5.3kPa)
What are the values of PṽO2 and PṽCO2 ?
Venous PO2- 40mmHg (5.3kPa)Venous CO2- 46mmHg (6.2kPa)
How does the air diffuse across the membranes between the alveoli and the blood circulation ?
Diffusion across the partial pressure gradient
What is the rate of diffusion across the membrane directly proportional to ?
The gas partial pressure gradient Gas solubility The available surface area
What is the rate of diffusion across the membrane inversely proportional to ?
The thickness of the membrane
What does gas need to be in, in order to be able to diffuse across the alveolar membrane ?
Gas needs to be in solution
What are the solubilities of O2 and CO2 ?
O2- not very soluble CO2- very soluble so van diffuse much faster
What gas (CO2 or O2) has the greatest pressure gradient ?
O2
Describe the overall rates of equilibrium of CO2 and O2 ?
Similar because of the greater pressure gradient for O2
How has the anatomy of the lung adapted to maximise gas exchange ?
Large surface area Minimum diffusion distance Thin cell membranes (type I alveolar cells, capillary)
What happens to the surface area of alveoli in emphysema ?
Reduced surface area
What are the features of fibrotic lung disease ?
Thickened alveolar membranes slows gas exchangeLoss of lung compliance (decrease) may decrease alveolar ventilation, increase in effort of inspirationDecrease in PO2increase in PCO2
What are the features of pulmonary oedema ?
Fluid in interstitial space increases diffusion distanceArterial pCO2 may remain normal due to higher solubility in waterImpact on PO2 in blood
What are features of Asthma ?
Increased airway resistance decreases airway ventilation because bronchioles are constricted
What are the features of emphysema ?
loss of surface area Major impact on diffusionIncrease in compliance, increase in effort of expirationDecrease in PO2Increase in PCO2
When is the rate of diffusion across the membrane most rapid ?
Over small distances
