O-I-A-N Posterior Shoulder Muscles

PT605 Anatomy, Oregon Tech

Origin: Trapezius

Inion process and superior nuchal line, SP’s of C1-7 via ligamentum nuchae, SP’s of T1-12 and supraspinous ligament.

Insertion: Trapezius

Lateral 1/3 border of clavicle, medial aspect of acromion process, and superior lip of spine of scapula.

Actions: Trapezius

Scapular elevation, retraction, upward rotation, depression, posterior tilt, and cervical extension, ipsilateral sidebending, and contralateral rotation.

Nerve: Trapezius

Spinal accessory nerve CrN XI, and DPR C3, C4.

Origin: Levator Scapulae

TP’s of C1-4.

Insertion: Levator Scapulae

Superior angle of scapula.

Actions: Levator Scapulae

Scapular elevation, retraction, downward rotation, and neck extension, ipsilateral sidebending, and ipsilateral rotation.

Nerve: Levator Scapulae

Dorsal scapular nerve C5, and VPR C3, C4.

Origin: Rhomboid Minor

SP’s of C6-7.

Insertion: Rhomboid Minor

Medial border of scapula opposite of smooth triangular space.

Actions: Rhomboid Minor

Scapular elevation, retraction, downward rotation.

Nerve: Rhomboid Minor

Dorsal scapular nerve C5.

Origin: Rhomboid Major

SP’s of T2-T5 and supraspinous ligament.

Insertion: Rhomboid Major

Medial border of scapula below smooth triangular space.

Actions: Rhomboid Major

Scapular elevation, retraction, and downward rotation.

Nerve: Rhomboid Major

Dorsal scapular nerve C5

Origin: Latissimus Dorsi

SP’s of T7-S5 and supraspinous ligament, ribs 9-12, thoracolumbar fascia, external lip of iliac crest, and sometimes inferior angle of scapula.

Insertion: Latissimus Dorsi

Floor of IT groove.

Action: Latissimus Dorsi

Shoulder extension, adduction, internal rotation, and sometimes scapular downward rotation.

Nerve: Latissimus Dorsi

Thoracodorsal nerve C6, C7, C8.

Origin: Teres Major

Lower 2/3 of lateral border of scapula.

Insertion: Teres Major

Medial lip of IT groove.

Actions: Teres Major

Shoulder extension, adduction, internal rotation, depresses the humeral head to allow for normal shoulder abduction, and holds the head of humerus in the glenoid fossa.

Nerve: Teres Major

Lower subscapular nerve C5, C6.

Origin: Supraspinatus

Supraspinous fossa.

Insertion: Supraspinatus

Superior facet of greater tubercle.

Actions: Supraspinatus

Shoulder abduction (first 15-30 deg), depresses the humeral head to allow for normal shoulder abduction, and holds the head of humerus in the glenoid fossa.

Nerve: Supraspinatus

Suprascapular nerve C5, C6.

Origin: Infraspinatus

Infraspinous fossa.

Insertion: Infraspinatus

Middle facet of greater tubercle.

Actions: Infraspinatus

Shoulder external rotation, depresses the humeral head to allow for normal shoulder abduction, and holds the head of humerus in the glenoid fossa.

Nerve: Infraspinatus

Suprascapular nerve C5, C6.

Origin: Teres Minor

Upper 1/3 of lateral border of scapula.

Insertion: Teres Minor

Inferior facet of greater tubercle.

Actions: Teres Minor

Shoulder extension, adduction, external rotation, depresses the humeral head to allow for normal shoulder abduction, and holds the head of humerus in the glenoid fossa.

Nerve: Teres Minor

Axillary nerve C5, C6.

Origin: Subscapularis

Subscapular fossa.

Insertion: Subscapularis

Lesser tubercle of humerus.

Actions: Subscapularis

Shoulder internal rotation, depresses the humeral head to allow for normal shoulder abduction, and holds the head of humerus in the glenoid fossa.

Nerve: Subscapularis

Upper subscapular nerve C5, C6, and lower subscapular nerve C5, C6.