The Mechanism of Breathing Flashcards
How is a the diffusion of gases across the alveolar epithelium maintained?
By moving air constantly in and out of the lungs in the process of breathing (ventilation)
When is air forced into the lungs?
When air pressure inside the lungs is less than the air pressure of the atmosphere
When is air forced out of the lungs?
When air pressure inside the lungs is more than the air pressure of the atmosphere
What is inspiration?
Inhalation
What is expiration?
Exhalation
Where is air forced in inspiration?
Into the lungs
Where is air forced in expiration?
Out of the lungs
What are the three muscles that act upon the air pressure in the lungs?
- the diaphragm
- the internal intercostal muscles
- the external intercostal muscles
What is the diaphragm?
A sheet of muscle that separates the thorax from the abdomen
Where do intercostal muscles lie?
Between the ribs
What does the contraction of the internal intercostal muscles lead to?
Expiration
What does the contraction of the external intercostal muscles lead to?
Inspiration
What is breathing in?
An active process
What happens to the intercostal muscles in inspiration?
External intercostal muscles contract and internal intercostal muscles relax
What happens to the ribs in inspiration?
The are pulled upwards and outwards (increasing thorax volume)
What happens to the diaphragm in inspiration?
It contracts causing it to flatten (increasing thorax volume)
What happens to the thorax in inspiration?
Increases in volume
What happens to lung pressure in inspiration?
Reduces
What is the relationship between pulmonary pressure and atmospheric pressure in inspiration?
Atmospheric pressure is greater than pulmonary pressure
Where is air forced in inspiration?
Into the lungs
What is breathing out?
A passive process
What happens to intercostal muscles in expiration?
Internal intercostal muscles contract and external intercostal muscles relax
What happens to the ribs in expiration?
The ribs move downwards and inwards (decreasing thorax volume)
What happens to the diaphragm in expiration?
They relax so it is pushed up by the contents of the abdomen that were compressed during inspiration (further decreasing thorax volume)
