External Gas Exchange Flashcards
Relationship between flow, pressure, and resistance
flow = pressure difference/resistance
Factors that affect alveolar gas exchange
- partial pressure gradients
- solubility coefficients
- membrane thickness
- membrane area
- ventilation-perfusion coupling
How does bronchial resistance affect airflow?
- constricted bronchioles = decreased airflow
- dilated bronchioles = increased airflow
How does partial pressure gradients affect alveolar gas exchange?
- gases move from areas of high partial pressure to areas of low partial pressure
- the larger the pressure gradient, the faster the gas exchange
How does solubility coefficients affect alveolar gas exchange?
gases with higher solubility in water diffuse more readily across the respiratory membrane
How does membrane thickness affect alveolar gas exchange?
thicker membranes increase the diffusion distance, slowing down gas exchange
How does membrane area affect alveolar gas exchange?
larger surface area allows for more gas exchange
How does ventilation-perfusion coupling affect alveolar gas exchange?
- matching the air flow to blood flow allows for maximum gas exchange
- poor ventilation causes blood flow to redirect to better-ventilated areas
What is ventilation-perfusion coupling?
process by which the amount of air reaching the alveoli matches the amount of blood flowing through the capillaries around said alveoli
What is Boyle’s law and how does it pertain to ventilation?
- at a constant temperature, the pressure of a gas is inversely proportional to its volume
- explains how we breathe; when the volume increases, the pressure inside the lungs decreases and vice versa
What is Charles’s law and how does it pertain to ventilation?
- at a constant pressure, the volume of a gas is directly proportional to its absolute temperature
- as inhaled air is warmed to body temperature within the lungs, its volume increases slightly
What is Dalton’s law and how does it pertain to ventilation?
- the total pressure exerted by a mixture of gases is the sum of the partial pressures of each individual gas
- helps us understand the partial pressures of oxygen and carbon dioxide in the air and in the alveoli, which drive gas exchange
What is Henry’s law and how does it pertain to ventilation?
- the amount of gas that dissolves in a liquid is proportional to its partial pressure and solubility
- the higher the partial pressure of oxygen in the alveoli, the more oxygen dissolves in the blood
Pneumothorax causes and effects
- air in the pleural cavity
Causes: puncture wound, medical procedure
Effects: reduced gas exchange, shortness of breath and chest pain
Atelectasis causes and effects
- collapse of part of all of a lung
Causes: airway blockage, external pressure on lung, lack of surfactant
Effects: hypoxemia, increased risk of infection, shortness of breath or cough
Residual volume function
- prevent alveolar collapse
- ensure continuous gas exchange
- stabilize alveolar environment
What is the respiratory membrane?
barrier between the alveolar air and the blood in the pulmonary capillaries
What 3 structures form the respiratory membrane?
- type I alveolar cell
- squamous endothelial cell
- basement membrane
How does the thickness of the respiratory membrane affect diffusion?
the shorter the distance gases have to diffuse, the faster the exchange
What is pulmonary compliance?
how easily your lungs can stretch and expand
What is high and low pulmonary compliance?
high: lungs inflate with minimal effort
low: lungs are stiff and inflate with more effort
Importance of pulmonary compliance
optimal pulmonary compliance allows for easy breathing and aids in gas exchange
Factors that reduce pulmonary compliance
degenerative lung diseases that stiffen the lungs with scar tissue
Intrapulmonary pressure changes relative to atmospheric pressure during breathing
inhaling: intrapulmonary pressure decreases causing air to flow into the lungs
exhaling: intrapulmonary pressure increases causing air to flow out of the lungs
