Origin-   lateral clavicle, acromion, spine of scapula

Insertion- deltoid tuberosity and lateral shaft of humerus

Nerve Supply- axillary nerve (C5-C6)

Blood Supply- posterior circumflex humeral artery (3rd part of axillary artery)

Action -abducts arm (supraspinatus helps); flex and medially rotate arm, extend and laterally rotates arm.

Origin- subscapular fossa

Insertion- lesser tubercle of humerus and adjacent capsule of shoulder joint

Nerve Supply- upper and lower subscapular nerve (C5-C6- posterior cord of brachial plexus

*teres major also is innervated by subscapular

Blood Supply- subscapular artery (largest branch of axillary artery-3rd part)

Action- medially rotates arm (most powerful medial rotator) helps stabilize shoulder joint.

Origin- supraspinous fossa

Insertion- greater tubercle and adjacent capsule of shoulder joint

Nerve Supply- suprascapular nerve (C5, C6- superior trunk of brachial plexus)

Blood Supply suprascapular artery of the thyrocervical trunk (branch of subclavian)

Action- Abducts arm at shoulder first 15 degrees then assists deltoid muscle and stabilizes shoulder joint.

Infraspinatus Muscle

Origin- infraspinous fossa

Insertion- greater tubercle of humerus and adjacent capsule of shoulder joint

Nerve Supply- suprascapular nerve (C5,C6- superior trunk of brachial plexus)

* suprascapular nerve travels between the superior transverse ligament(STL)  of the scapula and the suprascapular notch. Artery travels OVER STL, Nerve travels UNDER STL

Blood Supply- suprascapular artery (branch of thyrocervical trunk)

Action- laterally rotates arm and stabilizes shoulder joint.

Origin- superior part of lateral scapula

Insertion- greater tubercle and adjacent capsule of shoulder joint

Nerve Supply- axillary nerve (C5, C6)

Blood Supply- circumflex scapular artery (of subscapular artery)

Action- laterally rotates arm and stabilizes shoulder joint

Supraspinatus   (insertion:greater tubercle)

Infraspinatus     (insertion: greater tubercle)

Teres minor       (insertion: greater tubercle)

Subscapularis    (insertion:lesser tubercle)