Airway filtration and ventilation Flashcards
What is Dalton’s law?
The pressure of a gas mixture is equal to the sum of the individual gases (partial pressures)
How do the partial pressures differ between environment and lungs?
Slightly lower of each gas in lungs than atmosphere
What has to be taken out of account when calculating partial pressure in lungs, and why?
Water vapour, as the air in lungs is fully saturated with it and has its own partial pressure
What is equation of the pressure-volume relationship (Boyle’s law)?
P1V1 = P2V2
What is the relationship between pressure difference and airflow?
Directly proportional (higher pressure difference = higher airflow)
What is the relationship between resistance and airflow?
Inversely proportional (higher resistance = lower airflow)
What is viscosity of air affected by?
Humidity and concentration of air (e.g. high altitude)
What airways change their radius to change airflow?
Airways without rigid cartilage frame
What causes bronchodilation?
CO2 and Epi (beta-2 receptors)
What causes bronchoconstriction?
Histamine and parasympathetic stimulation (muscarinic receptors)
What diseases affect airflow?
Asthma, emphysema, chronic bronchitis
What does flow during inspiration/expiration depend on?
Creating on pressure difference between lungs and environment
What muscles increase lateral dimension of the rib cage?
External intercostal muscles (“bucket handle”)
What muscles increase anterior-posterior dimension of the rib cage?
Scalenes and sternocleidomastoids (“pump handle”)
What muscles activate during exercise or rapid breathing?
Internal intercostals and abdominals
How does the pleural sac prevent lungs from collapsing?
Fluid prevents two layers of sac from separating, with the outer layer attached to thoracic wall, and inner layer attached to rib
What must the relationship always be between alveolar pressure and intrapleural pressure?
Intrapleural pressure must be larger than alveolar
What is the function of the surfactant?
Contains proteins that disrupts forces between water molecules, reducing surface tension of alveolar walls, and increasing compliance of lungs, making alveolar spaces less prone to collapse
What is the relationship between surfactant and size of alveolus?
Positively correlative, so that pressure in each alveolus is equal in order to prevent alveoli from emptying into one another
What are the additional functions of the airways?
Change temperature of inspired air, humidify inspired air, filter inhaled foreign material
Why does inhaled air have to be humidified?
Dry air will dry out internal environment and make diffusion less efficient
How do the airways increase the temperature of inspired air?
Air passes through conchas of nasal cavity, which have high blood supply and so air can pass close by blood
How do the airways humidify inspired air?
Air passes through conchas of nasal cavity, which have high blood supply and so air can pass close by blood and be slightly humidified; glands secrete chemicals and humidify air
How do the airways filter inhaled air?
Goblet cells secrete mucus; mucus layer traps inhaled particles; watery saline layer allows cilia to push mucus towards pharynx; cilia move mucus to pharynx
