Breathing Flashcards
What happens during expiration?
Abdominal muscles (e.g. rectus abdominus) contracts which pushes the contents of the abdomen in which also forces the diaphragm upwards which reduces the volume in the thorax.
The internal intercostal muscles also contract which causes the ribs to move down which reduces the internal diameter of the thoracic cage.
What happens during inspiration?
Diaphragm contracts and shortens and flattens which pushes it down which increases the volume in the thorax. The increase in pressure also pushes the ribs out.
The external intercostal muscles also contract which raises the ribs which increases the diameter of the chest wall.
The Accessory muscles are also used during inspiration.
If you fill the lung at a given pressure, then block the lung airway, then change the pressure surrounding the lung, what will happen to the lung volume?
The lung volume is always proportionate to the surrounding air pressure. If the airways is cut off and then pressure surrounding the lung decreases, then the air inside the lungs will also decrease by a proportionate amount. The difference in pressure is therefore relative and will stay constant as pressure outside of the lung changes.
What is meant by the compliance of the lung?
What factors affect compliance?
The lung’s ability to stretch and expand. This is the change in volume per unit pressure.
Disease affects compliance. Compliance also increases with age generally due to a decrease in muscular strength and elastic recoil.
What is surfactant?
Reduces surface tension in the alveoli which prevents collapse of the alveoli at the end of expiration. This makes breathing easier.
It also reduces the compliance of the lung (makes the lung less stiff).
Reduces the tendency of alveoli oedema
Increases the stability of the lung (main reason)
What are the 3 intercostal muscles are what direction do they move in
External Intercostal muscles- hands in pockets
Internal Intercostal muscles- hands on tits
Innermost intercostal muscles- Vertically
