The Mechanics of Breathing and Lung Function Testing Flashcards Preview

ESA 3 - Respiratory System > The Mechanics of Breathing and Lung Function Testing > Flashcards

Flashcards in The Mechanics of Breathing and Lung Function Testing Deck (106)
Loading flashcards...

How is air drawn into the lungs? 

By expanding the volume of the thoracic cavity 


What is work done during breathing doing? 

Moving the structures of the lungs and thorax to overcome the resistance to flow of air through the airways 


What is the pleural space? 

The space bewteen the lungs and thoracic wall 


What is the pleural space normally filled with? 

A few millimetres of fluid 


What is the purpose of the fluid in the pleural space? 

The surface tension of which forms a pleural seal holding the outer surface of the lungs to the inner surface of the thoracic wall 


What is the result of the pleural fluid holding the lungs to the thoracic wall? 

The volume of the lungs changes with the volume of the thoracic cage


What happens if the integrity of the pleural seal is broken? 

The lungs will tend to collapse


What happens in a pneumothorax? 

Air gets in between the two layers of the pleura, fluid surface tension is lost and the lungs collapse 


What is meant by lung compliance? 

The 'stretchiness' of the lungs


What is lung compliance defined as? 

The volume change per unit pressure change 


What does high compliance mean? 

Lungs are easy to stretch 


How is compliance measured? 

By measuring the change in lung volume for a given pressure 


What does a greater lung volume mean for compliance? 

Greater compliance 


What is it more usual to calculate than compliance? 

Specific compliance 


Why is it more usual to measure specific compliance? 

Becasue, even with the constant elasticity of lung structures, compliance will also depend on the starting volume from which it is measured


How is specific compliance calculated? 

Volume change per unit pressure change / Starting volume of lungs 


Draw a diagram illustrating the compliance for; 

  • Elastic lungs
  • Normal lungs
  • Stiff lungs



What do the elastic properties of the lungs arise from? 

  • Elastic tissue in the lungs
  • Surface tension forces of the fluid lining the alveoli 


What is meant by surface tension?

The interactions between molecules at the surface of a liquid


What is the effect of surface tension on stretchiness?

It makes the surface resistant to stretching 


What does a higher surface tension mean for compliance?

The higher the surface tension, the harder the lungs are to stretch and therefore the lower the compliance 


What happens to the surface tension of the lungs at low lung volumes?

It is much lower than expected 


Why is the surface tension of the lungs much lower than expected at low lung volumes?

Due to the disruption of interactions between surface molecules by surfactant 


What produces surfactant in the lungs?

Type 2 alveolar cells 


What is surfactant?

A complex mixture of phospholipid and proteins, with detergent properties 


Where does the hydrophilic end of surfactant molecules lie?

In the alveolar fluid


Where does the hydrophobic end of surfactant molecules lie?

Projects into alveolar gas


What is the result of the position of the hydrophilic and hydrophobic ends of the surfactant molecule?

They float on the surface of the lining fluid, disrupting interaction between surface molecules 


When does surfactant reduce surface tension? 

When the lungs are deflated, but not when fully inflated 


What is the result of surfactant only reducing surface tension when the lungs are deflated? 

Little breaths are easy, and big breaths are hard, and it takes less force to expand small alveoli than it does large ones