Which Muscles Contract during Normal Expiration Quizlet
The Scalene muscles, which also move the chest wall and have a function when inhaled, are also intercostal muscles, but not one of the three main layers. The external and internal muscles are innervated by the intercostal nerves (the ventral rami of the thoracic spinal nerves), fed by the intercostal arteries and drained by the intercostal veins. Their fibers run in opposite directions. Intercostal muscles are many different groups of muscles that run between the ribs and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping to widen and reduce the size of the chest cavity. . . . .