Positions and Actions of Muscles – Anterior Trunk Muscles

Position and actions of the anterior trunk muscles.

Muscle name



Pectoralis major

covers the surface of the upper chest

Adducts and inwardly rotates the arm

Pectoralis minor

Beneath pectoralis major. Runs from the rib to the scapula.

Rotates the scapula downwards

Serratus anterior

Curved muscle at the side of the ribcage

Pulls the scapula forward

External oblique

Slants down from the lower ribs to the pelvic girdle

flexes, rotates, and bends the trunk.

Internal oblique

Beneath the external obliques

Flexes, rotates, and bends the trunk.

Rectus abdominis

Attaches to the pubic bone and stretches the length of the abdomen to the sternum

Supports the abdominal organs and flexes the vertebral column and trunk.

Transversus abdominis

Attaches to the inner surface of the ribs

Supports the abdominal organs


Dome shaped muscle that separates the abdominal cavity from the thoracic cavity

Assists breathing as contraction expands the volume of the thoracic cavity, allowing inspiration

External intercostals

Between the ribs, on the outside

Elevate the ribcage when breathing in

Internal intercostals

Between the ribs on the outside

Depresses the ribcage when breathing out.

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