The mechanism of breathing Flashcards
How to maintain diffusion of gases across the alveolar epithelium?
Air constantly moved in and out of the lungs - this is the process of breathing/ventilation.
What is inspiration (inhalation)?
When the air pressure in the atmosphere is greater than the pressure inside the lung and air is forced into the lungs.
What is expiration (exhalation)?
When the air pressure in the lungs is greater than the atmosphere so air is forced out of the lungs.
What muscles changes the pressure within the lungs?
1) Diaphragm - a sheet of muscle that separates the thorax from the abdomen.
2) Intercostal muscles - lies between the ribs, there are 2 sets of intercostal muscles:
* Internal intercostal muscles - contraction leads to expiration (breathing out). - points towards the inside.
* External intercostal muscles - contraction leads to inspiration (breathing in). - points towards the outside.
How does inspiration happen?
Inspiration is an active process so it requires energy
- The external intercostal muscles contract and internal intercostal muscles relax.
- The ribs are pulled upwards and outwards, increasing the volume of the thorax.
- The diaphragm muscles contract, causing it to flatten, increasing the volume of the thorax.
- Increase in volume of the thorax decrease the pressure in the lungs.
- Now the pressure in the atmosphere is higher than the pressure in the lung, therefore, it causes the air to be forced into the lungs.
How does expiration happen?
Expiration is a passive process so it does not require much energy
- The internal intercostal muscles contract and external intercostal muscles relax.
- The ribs move downwards and inwards, decreasing the volume of the thorax.
- The diaphragm muscles relax so it pushes up and become curved again so the volume of the thorax decreases.
- Decrease in the volume of the thorax increases the pressure in the lungs.
- The pressure in the lung is higher than the pressure in the atmosphere so air is forced out of the lungs.
