Re: Is a lung a muscle

Hi Hardie,  The lungs, although they have a pretty strenuous job to do, 
are not muscles. Each lung is encased in a thin membranacious material 
called the pleura.The driving force that makes them operate comes from the 
diaphram (which is a muscle), and the intercostal muscles between the ribs.
There are two sets of intercostal muscles between the ribs, internal and 
external.

When we breathe in, the diaphram contracts and flattens downwards and the 
external intercostal muscles contract, the pressure in the thorax drops 
which forces air into the lungs. Upon expiration the diaphram relaxes, 
moving upwards into a dome shape and the internal intercostal muscles 
contract which increases the internal pressure, forcing air out. Hope this 
is useful.