Pectoral Muscles

Front 1

Pectoralis Major
Origin / Insertion / Innervation (N) / Action

Back 1

Origin: Sternocostal head (mandibulum and ribs); claviciular head - medial third of clavicle.

Insertion: lateral lip of intertubercular sulcus

Nerve: Laterial Pectoral (C5-C6); Medial Pectoral (C8, T1)

Action: adduction, medial rotates head; sternocostal head extends humerous from flexed position; clavicular head flexes.

Front 2

Pectoralis Minor
Origin / Insertion / Innervation (N) / Action

Back 2

Origin: 3-5th ribs

Insertion: coracoid process of scapula

Nerver: Medial Pectoral Nerve (C8, T1)

Action: stabilize scapula, drawing inferiorly and anteriorly against thoracic wall.

Front 3

Subclavius
Origin / Insertion / Innervation (N) / Action

Back 3

O: sternalcostal joint of first rib.
I: middle third and inferior surface of clavicle.
N: subclavian n (or nerve of subclavius) (C5, C6)
A: depress and anchor clavicle.

Front 4

Serratus Anterior
Origin / Insertion / Innervation (N) / Action

Back 4

O: External & Lateral surface of ribs 1-8.
I: Anterior surface, medial border of scapula
N: Long Thoracic Nerve (C6, C7)
A: Rotates scapula (glenoid cavity superior), protracts scapula and holds against thoracic wall.

Front 5

Trapezius
Origin / Insertion / Innervation (N) / Action

Back 5

O: External occipital protuberance; nuchal line; nuchal ligament; spinous process of C7-T12 vertebra.
I: Lateral third of clavicle, acromion and spine of scapula.
N: Accessory Nerve (XI); Ventral Primary Rami (C3-C4)
A: elevates, depresses, retracts scapula; rotate glenoid fossa superiorly.

Front 6

Latissimus Dorsi
Origin / Insertion / Innervation (N) / Action

Back 6

O: Spinous process of 6 lower vertebra; thoracolumbar fascia; illiac crest (pelvis); inferior 3 ribs
I: Floor of intertubercular sulcus (medial/front side of humerus)
N: Thoracodorsal n (C6, C7)
A: extend, adducts, medial rotates humerus. raises body to arms (climbing)

Front 7

Levator Scapulea
Origin / Insertion / Innervation (N) / Action

Back 7

O: Transverse process of C1-C4 vertebra.
I: medial border of scapula above spine.
N: Dorsal Scapular n (C5); Cervical n (C3, C4)
A: elevate scapula; tilts glenoid fossa inferiorly.

Front 8

Rhomboid Minor & Major
Origin / Insertion / Innervation (N) / Action

Back 8

O: Minor: Spinous process of C7-T1; nuchal ligament
Major: Spinous process of T2-T5
I: Medial border of scapula (Triangular area)
N: Dorsal Scapular N (C5)
A: retract scapula and rotate it to depress glenoid cavity; fix scapula to thoracic wall.