Muscle Origin Insertion Action
Diaphragm circular line passing around inner surface wall of body; sternal: xiphoid process; costal: lower 6 ribs on either side; lumbar: L1-L3 Central tendon draws central tendon down during quiet inspiration
External intercostals inferior border of upper rib Superior border of rib below Draws central tendon down during quiet inspiration
Internal intercostals Superior border of rib below Inferior border of rib above Depresses ribs during expiration
Levatores costarum longi Transverse process of T7-T10 outer surface of second rib below orgin Depresses ribs during expiration
Levatores costarum breves Transverse process of C7-T11 outer surface of rib directly below origin Elevates rib during inspritation; extends vertebrae; lateral flexion; rotation to opposite side
Serratus posterior superior Spinous process of C7-T3 Superior borders of second - fifth ribs Elevates ribs; muscles used in inspiration
Serratus posterior inferior Spinous process of T11-T12; L1-L3 Inferior borders of lower four ribs Counteracts pull of diaphragm; aids in respiration
Transversus abdominis 2/3 of inner iliac crest; inner edges of lower six costal cartilages Linea alba Constricts abdominal contents; assists in forced expiration
Pyramidalis Ansterior aspect of symphysis pubis and pubic bone Linea alba Compresses abdomen; forced expiration