MECHANICS OF BREATHING
WHAT ARE THE MECHANICS OF BREATHING?
▪ The diaphragm flattens and moves downwards and the intercostal muscles move
the rib cage upwards and out.
▪ This increase in size decreases the internal air pressure and so air from the outside
(at a now higher pressure than inside the thorax) rushes into the lungs to balance
the pressures.
▪ Inspiration occurs when the diaphragm and the external intercostal muscles
contract.
▪ Expiration occurs when the diaphragm and the intercostal muscles relax.
▪ The contraction or relaxation of muscles around the lungs changes the entire
volume of air inside the lungs, and so does the pressure.
As seen, the
diaphragm has
contracted in the first
diagram to make space
for the lungs, and the
diaphragm has relaxed
in the second diagram
as the chest contracts.
INTERCOSTAL MUSCLES
▪ The intercostal muscles are found between the ribs and they control rib
movement.
▪ 1) Diaphragm contracts and moves downwards.
▪ 2) Intercostal muscles contract and move the ribs upwards and outwards.
These muscles help in
rib functioning during
breathing
ROLE OF MUSCLES DURING NORMAL BREATHING
There are
2 types of
muscles
involved
Muscles of
inspiration
Muscles of
expiration
END OF PRESENTATION