6.7- THE MECHANISM OF BREATHING Flashcards
What is done to maintain diffusion of gases across the alveolar epithelium?
air constantly moved in and out of lungs
What is the process of air constantly moving in and out of the lungs called?
breathing or ventilation
When is air forced into the lungs?
when air pressure of atmosphere greater than air pressure inside lungs
What is the process of air being forced into the lungs called?
inspiration (inhalation)
When is air forced out of the lungs?
when air pressure in lungs greater than that of atmosphere
What is the process of air being forced out of the lungs called?
expiration (exhalation)
What are the three sets of muscles that cause the pressure change within the lungs?
diaphragm
internal intercostal muscles
external intercostal muscles
What is the diaphragm?
sheet of muscle that separated the thorax from the abdomen
Where does the intercostal muscles lie between?
between the ribs
What does the contractions of the internal intercostal muscles lead to?
contraction leads to expiration
What does the contraction of external intercostal muscles lead to?
contraction leads to inspiration
What sort of process is breathing in?
active process
Why is breathing in an active process?
it uses energy
How breathing in occurs: intercostal muscles (1)
external intercostal muscles contract, while internal intercostal muscles relax
How breathing in occurs: ribs (2)
ribs pulled upwards + outwards, increasing volume of thorax
How breathing in occurs: diaphragm (3)
diaphragm muscles contract, causing it to flatten, which also increases volume of thorax
How breathing in occurs: increased volume of thorax (4)
increased volume of thorax results in reduction of pressure in lungs
How breathing in occurs: atmospheric pressure (5)
atmospheric pressure now greater than pulmonary pressure + air forced into lungs
What sort of process is breathing out?
largely passive process
Why is breathing out a largely passive process?
does not require much energy
How breathing out occurs: intercostal muscles (1)
internal intercostal muscles contract, while external intercostal muscles relax
How breathing out occurs: ribs (2)
ribs move downwards + inwards, decreasing volume of thorax
How breathing out occurs: diaphragm (3)
diaphragm muscles relax + so it’s pushed up again by contents of abdomen that were compressed during inspiration
volume of thorax further decreased
How breathing out occurs: decreased volume of thorax (4)
decreased volume of thorax increases pressure in lungs
How breathing out occurs: pulmonary pressure (5)
pulmonary pressure now greater than that of atmosphere, + so air forced out of lungs
What is the main cause of air being forced out during normal quiet breathing?
recoil of elastic tissue in lungs
When do the various muscles play a major part in breathing?
only under more strenuous conditions i.e. exercise
