Question

How does Boyle's law explain the mechanisms of ventilation (i.e. inpspiration vs. expiration, pressure differences, etc.)?

Answer 1

Boyle's law states that the pressure of the gas is indirectly proportional to the volume. It means if the space is reduced then the pressure will increase & vice versa.

How the Boyle's law related to the respiratory system?

Its by means of the pressure variation.

what types of pressure changes are happen there?

Very important thing in the respiration is the pressure changes in between the atmosphere and lungs. This changes is actually causing the flow of air in & out of the lungs.

Three main pressures which responsible for this process.

1. Atmospheric pressure

2. Intra alveolar pressure

3. Intra pleural pressure

Atmospheric pressure is simply a pressure exerted by atmosphere ( air surrounded us) & its referred as 760mm Hg. This iis constant.

Intra alveolar pressure is presents in the alveoli of the lungs. It is open and connected to the atmospheric pressure and so its equal means neutralized each other unless we breathe.

Intra pleural pressure is exerted by the pleural cavity space inbetwren the visceral & parietal layer. Its always negative.

Where the pressure changes starts actually ? & how relates the Boyle's law?

Its started at the moment we initiate the respiratory process. Our brain sends signals to the respiratory muscles to inhale the air. Muscles of inspiration getting activated, diaphragm contracts & moves downward incostal muscles causes the ribcage expansion....all those results in the increase thoracic cavity space.

As already said, the alveolar & atmospheric pressure is neutral as they connected through the airway.

If the inhalation starts, the lung expands the volume is increased here & it cause changes in pressure ( as the volume increases the pressure drops - Boyle's law). It results in flow of air from atmosphere into lungs.

Now the alveoli is filled with air & the gaseous exchange started.

How about the expiration then?

At the end of inspiration the lungs expands and pressure is higher now. Once expiration started, thoracic cavity comes back to its size ( reduces the volume). According to Boyle's law, volume reduces the pressure increases. So here the pressure increases higher than the atmospheric pressure and rushes the air out of lungs.

Conclusion:

Pressure changes is the main reason. We should always remember the point that "pressure in inversely proportional to its volume". & between a two medium ( lungs & atmosphere), the flow of gas ( air) always from a high pressure area to the low pressure area.