Diaphragm and intercostal muscles.
There are 11 pairs of intercostal muscles on each side (22 total muscles). The intercostal muscles lie between the ribs.
intercostal muscle
The Phrenic Nerve-Diaphragm and the External Intercostal Nerve-External intercostal muscles
The intercostal muscles. Intercostal means "between ribs".
The internal intercostal muscles relax and the external intercostal muscles contract, pulling the ribcage upwards and outwards.
The intercostal muscles are the muscles that lie between the ribs and form the chest wall. Their function is to aid inhalation and exhalation.
Intercostal Muscles
Intercostal muscles are several groups of muscles that run between the ribs, and help form and move the chestwall. The intercostal muscles are mainly involved in the mechanical aspect of breathing. These muscles help expand and shrink the size of the chest cavity to facilitate breathing.
The diaphragm and external intercostal muscles are primarily involved in changing the thoracic volume during breathing. The diaphragm contracts during inhalation to increase thoracic volume, while the external intercostal muscles help lift and expand the rib cage.
The external intercostal muscles run between the ribs. They are responsible for elevating the ribs during inhalation. The internal intercostal muscles are situated deeper and help with forced exhalation by depressing the ribs.
There are 11 pairs of external intercostal muscles in humans. These muscles are located between the ribs and are involved in expanding the chest cavity during inhalation.