Airway filtration and ventilation

Question 1

What is Dalton’s law?

Answer 1

The pressure of a gas mixture is equal to the sum of the individual gases (partial pressures)

Question 2

How do the partial pressures differ between environment and lungs?

Answer 2

Slightly lower of each gas in lungs than atmosphere

Question 3

What has to be taken out of account when calculating partial pressure in lungs, and why?

Answer 3

Water vapour, as the air in lungs is fully saturated with it and has its own partial pressure

Question 4

What is equation of the pressure-volume relationship (Boyle’s law)?

Answer 4

P1V1 = P2V2

Question 5

What is the relationship between pressure difference and airflow?

Answer 5

Directly proportional (higher pressure difference = higher airflow)

Question 6

What is the relationship between resistance and airflow?

Answer 6

Inversely proportional (higher resistance = lower airflow)

Question 7

What is viscosity of air affected by?

Answer 7

Humidity and concentration of air (e.g. high altitude)

Question 8

What airways change their radius to change airflow?

Answer 8

Airways without rigid cartilage frame

Question 9

What causes bronchodilation?

Answer 9

CO2 and Epi (beta-2 receptors)

Question 10

What causes bronchoconstriction?

Answer 10

Histamine and parasympathetic stimulation (muscarinic receptors)

Question 11

What diseases affect airflow?

Answer 11

Asthma, emphysema, chronic bronchitis

Question 12

What does flow during inspiration/expiration depend on?

Answer 12

Creating on pressure difference between lungs and environment

Question 13

What muscles increase lateral dimension of the rib cage?

Answer 13

External intercostal muscles (“bucket handle”)

Question 14

What muscles increase anterior-posterior dimension of the rib cage?

Answer 14

Scalenes and sternocleidomastoids (“pump handle”)

Question 15

What muscles activate during exercise or rapid breathing?

Answer 15

Internal intercostals and abdominals

Question 16

How does the pleural sac prevent lungs from collapsing?

Answer 16

Fluid prevents two layers of sac from separating, with the outer layer attached to thoracic wall, and inner layer attached to rib

Question 17

What must the relationship always be between alveolar pressure and intrapleural pressure?

Answer 17

Intrapleural pressure must be larger than alveolar

Question 18

What is the function of the surfactant?

Answer 18

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

Question 19

What is the relationship between surfactant and size of alveolus?

Answer 19

Positively correlative, so that pressure in each alveolus is equal in order to prevent alveoli from emptying into one another

Question 20

What are the additional functions of the airways?

Answer 20

Change temperature of inspired air, humidify inspired air, filter inhaled foreign material

Question 21

Why does inhaled air have to be humidified?

Answer 21

Dry air will dry out internal environment and make diffusion less efficient

Question 22

How do the airways increase the temperature of inspired air?

Answer 22

Air passes through conchas of nasal cavity, which have high blood supply and so air can pass close by blood

Question 23

How do the airways humidify inspired air?

Answer 23

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

Question 24

How do the airways filter inhaled air?

Answer 24

Goblet cells secrete mucus; mucus layer traps inhaled particles; watery saline layer allows cilia to push mucus towards pharynx; cilia move mucus to pharynx