Respiratory Physiology: Ventilation, Gas Exchange, and Pressure Laws

What are the two major reasons we breathe?

To obtain oxygen for cellular respiration and to remove carbon dioxide.

What is pulmonary ventilation?

The movement of air in and out of the lungs.

What is external respiration?

The exchange of O2 and CO2 between the lungs and blood.

What is internal respiration?

The exchange of O2 and CO2 between blood and tissues.

What does spirometry measure?

The volume of exhaled and inhaled air.

What is the typical tidal volume for an average male or female?

~500 mL.

What structures make up the lower respiratory system?

Conducting and respiratory zone structures.

What is the function of the conducting zone?

To transport gas to and from gas exchange sites while cleansing, warming, and humidifying air.

What is the respiratory zone?

The site of gas exchange, consisting of structures like respiratory bronchioles, alveolar ducts, and alveoli.

What is atmospheric pressure (Patm)?

The pressure exerted by gases surrounding the body, typically 760 mmHg at sea level.

What is negative respiratory pressure?

When pressure is lower than atmospheric pressure (Patm).

What causes air to rush into the lungs during inspiration?

Negative intrapulmonary pressure.

What is Boyle's Law?

P1V1 = P2V2, describing the relationship between pressure and volume of gases.

What is Dalton's law of partial pressures?

The total pressure exerted by a mixture of gases is equal to the sum of the pressures exerted by each gas.

How is the partial pressure of nitrogen (PN2) calculated?

By multiplying its percentage in the air (78.6%) by the total atmospheric pressure (760 mmHg).

What is Henry's law?

Each gas will dissolve in a liquid in proportion to its partial pressure when in contact with liquids.

Why do alveoli contain more CO2 and water vapor than atmospheric air?

Due to gas exchanges in the lungs where O2 diffuses out and CO2 diffuses in.

What is the thickness of the respiratory membrane?

Very thin, approximately 0.5 to 1 µm thick.

How long is blood in contact with inspired air for gas exchange?

About 0.75 seconds, needing approximately 0.25 seconds to gain as much O2 as possible.