Name.

Position.

Origin.

Insertion.

Action.

Nerve Supply.

Pectoralis

major.

Upper and fore part of chest, and in front of axilla.

Anterior surface of sternum, clavicle, seven upper costal cartilages.

Outer margin occipital groove of humerus.

Flexes arm, raises body to arms, rotates inwards, adducts.

External anterior thoracic.

Pectoralis

minor.

Under pectoralis major.

Third, fourth, fifth ribs.

Coracoid process scapula.

Depresses point of shoulder.

Internal anterior thoracic.

Subclavius.

Between clavicle and first rib.

Cartilage, first rib.

Under surface clavicle.

Draws down clavicle.

From fifth and sixth cervical.

Serratus

magnus.

Between ribs and scapula at upper part and side of chest.

Eight upper ribs.

Vertebral border of scapula.

Extends arm forwards, assists in raising ribs in inspiration.

Posterior

thoracic.

External intercostals (eleven in number).

Fills intercostal spaces.

Inferior borders of ribs.

Superior borders of ribs below.

Raises ribs in expiration.

Intercostal.

Internal intercostals (eleven in number).

Fills intercostal spaces.

Inferior borders of ribs.

Superior borders of ribs below.

Depresses ribs in inspiration.

Intercostal.

Triangularis

sterni.

Inner wall of front of chest.

Lower third, posterior surface of sternum, ensiform cartilage, costal cartilage of four lower true ribs.

By digitations into lower borders of costal cartilages of second to sixth rib.

Draws down costal cartilages in expiration.

Intercostal.

Levators costarum (twelve in number).

On the back between seventh cervical and eleven upper dorsal vertebrae.

Transverse process, seventh cervical and eleven upper dorsal vertebrae.

Each to the rib below.

Raise ribs in inspiration.

Intercostal.

Diaphragm.

Forms floor of thorax and roof of abdomen.

Ensiform cartilage, six lower ribs, bodies of lumbar vertebrae.

into central tendon.

Respiration and expulsion.

Phrenic, lower intercostals, and phrenic flexus.