Muscles of Pectoral Girdle

Pec major

Origin: Clavicle (upper) and sternum (lower)

Insertion: Crest of Greater tubercle

Action: Shoulder flexion and IR (upper) and shoulder extension (lower but from an already flexed position)

Innervation:

Upper fibers (Lateral pectoral nerve; C5, C6, C7)

Lower fibers: medial and lateral pectoral nerves; C6, C7, C8, T1

Pec minor

O: Ribs 3-5

I: Coracoid process

A: Tilts scapula anteriorly and elevates ribs to assist with ventilation

N: Medial Pec nerve (C7, C8)

Subclavius

O: First rib

I: Inferior surface, middle part of clavicle

A: anchor and depress clavicle

N: Nerve to subclavius (C5, C6)

Serratus Anterior

O: Ribs 1-8

I: Medial border of scapula (costal)

A: scapular protraction and upward rotation

Fixed origin: scapular protraction (abduction and external rotation), upward rotation of the inferior angle, and contracts to hold the medial border of the scapula firmly against the rib cage.

Humerus fixed in flexion: the muscle acts to displace the thorax posteriorly

N: Long thoracic nerve (C5, C6, C7)

Trapezius

O:

upper fibers (external occipital protuberance, medial 1/3 of superior nuchalline, ligamentum nuchae and spinous process of C7 vertebra)

Middle fibers (spinous process of T1-T5)

Lower fibers (spinous processes of T6-T12)

I:

Upper: lateral 1/3 of clavicle and acromion process

Middle: Medial margin of acromion and superior lip of spine of scapula

Lower: tubercle at apex of spine of scapula

A:

Upper: Elevation of scap

Middle: retraction of scap

Lower: depression of scap

N: spinal accessory nerve (C3 and C4)

Latissimus dorsi

O: T6-T12, fascia, posterior lip of iliac crest, ribs 9-12 and inferior angle of scapula

I: Floor of intertubercular sulcus of humerus

A: shoulder adduction, internal rotation, extension, hyperextension of spine and anterior pelvic tilt

N: Thoracodorsal nerve C6, C7, C8

Levator scapulae

O: Posterior tubercles of transverse processes of C1-C4

I: Medial border of scapula, between superior angle and root of spine

A: Elevation and downward rotation of scapula, lateral flexion and ipsilateral rotation of cervical spine, extension of cervical spine

N: Dorsal scpular nerve; C5

Cerivical spinal Nerves C3, C4

Rhomboid major

O: spinous processes of T2-5 vertebrae

I: medial border of scapula between level of scapular spine and inferior angle

A: Scapular retraction, elevation and downward rotation

N: Dorsla scapular nerve C5

Rhomboid minor

O: Nuchal ligament, Spinous processes of C7-T1 vertebrae

I: Medial border at root of spine of scapula

A: scapular retraction and downward rotation

N: Dorsal scapular nerve C5

Teres major

O: dorsal surface of inferior angle and lower 1/3 of latera border of scapula

I: crest of lesser tubercle (medial lip of intertubercular sulcus)of humerus

A: glenohumeral adduction, internal rotation, and extension

N: Lower subscapular nerve; C5, C6

Deltoid

O: Anterior fibers: anterior border, superior surface, lateral 1/3 of clavicle

Middle fibers: lateral margin and superior surface of the acromion on the scapula

Posterior fibers: inferior lip of the posterior border of the spine of scapula

I: Deltoid tuberosity

A: All fibers active during shoulder abduction

anterior: shoulder flexion and IR

Middle: shoulder abduction

Posterior: shoulder extension and shoulder ER

N: axillary nerve, C5, C6

Supraspinatus

O: medial 2/3 of supraspinous fossa on the scapula

I: superior facet of greater tubercle on the humerus and shoulder joint capsule

A: initiates the 1st 15° of shoulder abduction and stabilizes the head of the humerus in the glenoid cavity during shoulder movements.

N: suprascapular nerve; C5

Infraspinatus

O: medial 2/3 of infraspinous fossa on the scapula

I: middle facet of the greater tubercle on the humerus and shoulder joint capsule

A: glenohumeral external rotation and stabilizes the head of the humerus in the glenoid cavity during shoulder movements

N: suprascapular nerve; C5, C6

Teres minor

O: upper 2/3, dorsal surface of the lateral border of the scapula

I: inferior facet of greater tubercle on the humerus and shoulder joint capsule

A: glenohumeral external rotation and stabilizes the head of the humerus in the glenoid cavity during shoulder movements.

N: Axillary nerve; C5, C6

Subscapularis

O: subscapular fossa of scapula

I: lesser tubercle of humerus and shoulder joint capsule

A: glenohumeral internal rotation and stabilizes the head ofthe humerus in the glenoid cavity during shoulder movements.

N: upper and lower subscapular nerves; C5, C6