Mechanics of Pulmonary Ventilation Flashcards Preview

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Flashcards in Mechanics of Pulmonary Ventilation Deck (24):

What is Boyles law?

Pressure varies inversely with volume


Why is Boyles law applicable to breathing?

Volume changes within the thoracic cavity create a pressure difference between inside pressure and atmospheric pressure, causing air to flow down it [gradient] in or out of the body


When is inside pressure = to outside pressure?

When there is no breathing. 760mmHg in the lung and outside


How do you get air into the lungs?

Decrease pressure and Increase volume
-greater volume= more space = decrease pressure = air flow in


What allows the increase of volume within the thoracic cavity?

The external intercostal muscles and the Diaphragm


How does the increase in volume in the thoracic cavity happen?

Diaphragm: accounts for 75% of the volume increase
-muscle contracts to pull down the diaphragm

External intercostal muscle: Muscle contracts allowing the thoracic wall (ribs) to expand up and out


How do you get air out of the lungs?

Decrease volume and increase pressure
-decrease volume=less air space=increases pressure =air flows out


What allows the decrease in volume in the thoracic cavity?

Relaxing of the external intercostal muscles and the diaphragm


How does the decrease in volume in the thoracic cavity happen?

Diaphragm gets pulled back up, external intercostal muscle stop contracting


How does inhalation during exercise differ from inhalation at rest?

The more forceful the inhalation causes the diaphragm to pull deeper, creating more volume space
-everything else is the same


How does exhalation during exercise differ from exhalation at rest?

Internal intercostal muscles contract causing the thoracic wall (ribs) to contract down and in (opposite to external intercostal muscles)

Oblique muscles contract

Rectus abdominus contracts (6pack)
-when contracts, causes the organs underneath to shift a little helping to push the diaphragm back up


Do the lungs fully deflate?

Never no matter how hard you exhale


Why don't the lungs fully deflate?

Due to the intrapleural pressure in the intratpleural space


Why is having intraleural pressure advantageous?

Lungs don't collapse even at the end of expiration

Allows for easy expansion of the lung, and there is no resistance against inflation


What happens during a pneumothorax?

When interleura pressure and intrapulmonary pressure become the same pressure by the lung tissue springing back into the chest cavity (causing collapse) and the thoracic wall springing outward


What are the 2 ways in which you can get a pneumothorax?

1. Hole in visceral pleura: Gas will flow from high to low until pressures are the same . Causing the lung to collapse

2. Hole through chest wall/periatal pleura: Air goes from the environment into the body

-in both cases the intrapleural space goes from only having fluid to having fluid and air


What is lung compliance?

Change in lung volume which is due to change in lung pressure
-how much pressure needed to fill the lung


What is compliance?

The stretchability of the lung
-More compliant the lung, the easier it is to stretch and increase volume during inhalation


What 2 factors influence the compliance of the lung?

Elastic tissue components of the lung

Surface tension inside the alveoli


Why does having too much elastin (elastic tissue) a bad thing?

If you have too much elastin it will become harder for the lung to expand enough, decreasing the compliance


What is surface tension?

Force that develops at the surface of a liquid due to the attraction between water molecules


What is surfactant?

Protein+ phospholipids that make a thin layer over the liquid in the alveoli.


What does surfactant do?

Prevents H2O molecules from sticking together

Prevents lung collapse

Increases compliance


Which group of people dose not having enough surfactant affect?

-dont have fully developed lungs and can not make enough surfactant to have a normal compliant lung