Mechanics Of Breathing Flashcards
Which extra muscles are needed for deep inspiration?
Sternocleiodomastoid (elevates the sternum) Middle, anterior and posterior scalene (elevate and fix the upper ribs)
Which muscles are used in normal inspiration?
External intercostals Diaphragm Interchondral parts of internal intercostal muscles
Which muscles are required for normal expiration?
None Results from passive recoil of the lungs and ribcage Expiration is passive
Which muscles are required forced expiration?
Internal intercostals Rectus abdominis External and internal obliques Transversus abdominis
What is a pneumothorax?
When the integrity of the pleural sac is broken by air, causing the lungs to collapse
What is in the pleural space?
Fluid
What holds the lungs to the thoracic wall?
Surface tension of the fluid in the pleural space
Define compliance of the lungs
Stretchiness of the lungs So equals the volume change per unit of pressure change
What does it mean if the lungs have a high compliance?
The lungs are easier to stretch
How does compliance change with lung volume?
The greater the lung volume, the greater the compliance
What are the main factors that affect compliance of the lungs?
Surface tension Surfactant Bubbles
How does surface tension affect the compliance of the lungs?
Interactions between molecules at the surface of a liquid makes the surface resist stretching
As surface tension increases, how does this affect lung compliance?
As Durga e tension increases, the harder the lungs are to stretch
Why is the surface tension of the lungs much lower than expected than if lungs were lined with saline?
Presence of surfactant
How does surfactant reduce surface tension?
Disrupts interactions between the surface molecules The hydrophilic ends of molecules lie in alveolar fluid while the hydrophobic ends project into alveolar gas
What is surfactant?
A mixture of phospholipids and proteins
What is surfactant produced by?
Type II alveolar cells
What is hysteresis?
The energy put into stretching a film of surfactant is not all recovered when the film recoils because need to overcome the surface tension when inhaling https://uk.answers.yahoo.com/question/index?qid=20100605085048AAbWQGy
When is the energy loss in hysteresis greatest?
When tidal volume is maximal - reason why little breaths are best
What is the equilibrium in a bubble?
When the film shrinks around gas until an equilibrium between tension and pressure is reached
What is Laplace’s law?
Pressure is inversely related to the radius of the bubble As radius increases, pressure decreases Bigger the bubble, lower the pressure
What will happen if a big bubble is connected to a smaller bubble?
Air will flow from high to low pressure -small bubble collapses into the big bubble
What prevents the alveoli (bubbles) from swallowing eachother and how?
Surfactant Keeps a high pressure in the larger bubbles As alveoli get bigger, the surface tension increases because surfactant is less effective - stops them eating the little bubbles
What is respiratory distress syndrome?
When premature babies have too little surfactant in their lungs so they are very stiff with fewer, larger alveoli. Breathing and gas exchange is compromised.
