In: Anatomy and Physiology
The muscles involved in ventialtion are
Inspiratory muscles
Expiratory muscles
Muscles of breathing:
Muscles working on breathing were attached in the thoracic cage. Those muscles forms the wall of thorax.
They works always as long as we can live. In that way respiratory muscles are different from other skeletal muscles.
According to the breathing, we divides the muscle into two groups
Inspiratory muscles:
Various muscles are working during the inspiration. But the Primary muscle of inspiration is Diaphragm.
and another one is External intercostalis.
Other than the above primary muscles, there are some other muscles which supports during inspiration are,
How these muscles works during inspiration?
Let starts from the motor signals,
The brain sends signals to the inspiratory muscles & they started to contract. As we already konw, the respiration happens because of the pressure changes inbetween the atmosphere & lungs.
The inspiratory muscles work in the way to cause those pressure changes.
How?
This is what we called pump handle & bucket handle movements. In the absence of breathe the atmospheric pressure & alveolar pressure were equal.
Once we inhaled, the muscles increases the size. It causes fall in pressure , becomes negative. So the air flows into llungs.
These changes are,
Diaphragm contracts & descends , increases the space in vertical diameter.
External intercostalis contracts , pulls the ribs outwards & upwards. It results in the increased size both in anteroposterior & transverse diameter.
The accessory muscles are also helps, sclalene works on the upper ribe cage.
Expiratory muscles:
At end of inspiration, gaseous exchange finished. Inspiratory muscles becomes relaxed. So the size of thoracic cage backs to normal. Reduced volume causes more pressure and it pushes the air out of lungs means expiration.
As we know, expiration is a passive process. So there is no much work on quite breathing. But incase of heavy breathing those muscles will work.
Work of expiratory muscles:
Simply they brings back to the normal size. But the air filled at end of inspiration makes the alveoli pressure becomes more postive.
So the air moves out to lungs.
The abdominal muscles assists in the heavy breathing by contracts & pushes the diaphragm upwards. This also causes the pressure changes hepls to exhalation.
Note: incase of extreme activities or stress, some other muscles also indirectly supports the breathing such as sternocleidomastoid, subclavious, pectoral muscles as they attached to the thoracic bones.