Principle muscle of trunk

Internal and External Intercostals

Diaphragm

Perineum

Levator ani

Sacrospinalis

External abdominal oblique

elevate ribs and enlarge thoracic cavity attached to a fill the spaces between the ribs (lie at angles in opposite directions to each other)

floor of pelvis, provides support (horizontal lie near genitalia)

extends vertebral column to produce erect posture (long and thick below the trapezium and latissimus)

dome forms the partition between the thoracic cavity and abdominal cavity below (moves down with inhalation)

Compresses abdominal cavity, expel substances from body, and flex spinal column.

aids defecation, support the pelvic viscera (posterior from tip of the coccyx to the anal canal)