Flashcards in BIOL 0800 Reading- Chapter 13 Deck (113)
What is the law of Laplace?
P = 2T/r
Why do alveoli of different sizes exist?
Because of Laplace's law: if the radius is smaller, then the surfactant is denser and surface tension is less, which allows for a higher pressure to prevent the small alveolus from condensing into larger ones
How does transpulmonary pressure affect resistance?
Increase in transpulmonary pressure increases airway radius, and airway resistance is decreased (inspiration)
What is lateral traction?
When the elastic connective-tissue fibers around the alveolar tissue help pull the airways open when the lungs pull on them.
How does epinephrine affect airway resistance?
Relaxes airway smooth muscle through beta-adrenergic receptors
What substance contracts airways to increase airway resistance?
Leukotriene, an eicosanoid
What is the tidal volume?
The volume of air taken in during a single expiration; usually the same volume as is expired
What is the inspiratory reserve volume (IRV)?
The maximal amount of air that can be increased above TV
What is functional reserve capacity (FRC)?
The amount of air left in the lungs after a normal tidal expiration: ERV + RV
What is expiratory reserve volume (ERV)?
The maximal amount of air that can be expired below TV
What is residual volume?
The amount of air remaining in the lungs after maximum expiration
What is the function of residual volume?
Keeps alveoli inflates between breaths, mixes with fresh air on next inspiration
What is the vital capacity (VC)?
The maximum amount of air you can exhale after a maximum inspiration; ERV + TV + IRV
What is inspiratory capacity (IC)?
Maximum amount of air that can be inhaled after a normal tidal expiration; RV + ERV
What is minute ventilation?
Total ventilation per minute: TB x RR (respiratory rate)
What is the approximate minute ventilation of a normal person?
6 L: (0.5 TV)(12 breaths each minute)
What is anatomical dead space?
The space within the airways that doesn't permit gas exchange
How do you calculate how much fresh air enters the lungs?
TV - deadspace = fresh air volume
What is alveolar ventilation?
The total volume of fresh air entering the alveoli per minute: = (TV - deadspace)(respiratory rate)
Why is breathing depth more important than breathing frequency to increase alveolar ventilation?
Because you still need to overcome dead space
What is alveolar dead space?
The volume of air that isn't used for gas exchange because alveoli have little or no blood supply; small in normal lungs
What is physiological dead space?
The sum of anatomical and alveolar dead space
What is the respiratory quotient?
The ratio of CO2 produced to O2 consumed; approximately 0.8
What is Dalton's law?
The sum of all the partial pressures of gases is the total pressure, since the pressures of different gases don't depend on each other
What is Henry's law?
The amount of gas dissolved in a liquid will be directly proportional to the partial pressure of the gas with which the liquid is in equilibrium; partial pressures at equilibrium of a gas in liquid and gas phases is identical
What are normal alveolar gas pressures?
105 for oxygen, 40 of CO2
Why are air pressures of O2 and CO2 different from alveolar pressures?
Because of diffusion in the pulmonary capillaries
What are three factors that determine the precise value of alveolar PO2?
PO2 of atmospheric air (decreased causes decrease); rate of alveolar ventilation (decreased causes decrease); rate of oxygen consumption (increased causes decrease) assuming only one factor changes at a time
What is hypoventilation?
When alveolar ventilation can't keep up with CO2 production: increase in PCO2