Major Muscles of Respiration

Diaphragm

Flattens during contraction, which expands thoracic cavity and compresses abdominal viscera during inspiration origin - ribs 7-12, xiphoid and lumbar vert insertion - central tendon of diaphragm

Internal intercostals

depresses ribs, which compresses thoracic cavity during forced expiration origin - superior border of inferior rib insertion - inferior border of superior rib

major muscles of inspiration

diaphragm and external intercostals

External intercostals

elevates ribs, which expands thoracic cavity during inspiration origin - inferior border of superior rib insertion - superior border of inferior rib

primary muscle for forced expiration

internal intercostals

accessory muscles in respiration

sternocleidomastoid scalenes pectoralis minor rectus abdominis external obliqu