Deep Muscles of the Shoulder

Anterior Muscles

- pectoralis minor - subclavius

Rhomboid Major

ORIGIN: Spinous processes of the vertebrae T2 - T5. INSERTION: Medial margin of the scapula inferior to the spine. ACTION: Stabilization, retraction, elevation and internal rotation of the scapula. NERVE SUPPLY: Dorsal scapular nerve (C4-C5). ARTERIAL SUPPLY: Dorsal scapular artery.

Serratus Anterior

ORIGIN: Superior: the 1st and 2nd ribs; Intermediate: the 2nd and 3rd ribs; Inferior: the 4th and 9th ribs. INSERTION: Medial margin of the anterior surface of the scapula. ACTION: Superior external rotation of the scapula; draws the scapula internally and forwards (THINK OF SERRATUS PUNCHES); Lowers the arm from a raised position; Elevation of the ribs. NERVE SUPPLY: Long thoracic nerve and the brachial plexus (C5-C7). ARTERIAL SUPPLY: Lateral thoracic artery.

Levator Scapulae

ORIGIN: Transverse process of vertebrae C1-C4. INSERTION: Superior angle to the medial border of the scapula. ACTION: Involved in flexing the head and neck laterally. NERVE SUPPLY: Dorsal scapular nerve (C5); C3 nerve; C4 nerve. ARTERIAL SUPPLY: Transverse cervical artery; ascending cervical artery

Teres Minor

ORIGIN: Upper two-thirds of the lateral margin of the scapula. INSERTION: Greater tubercle of the humerus. ACTION: External rotation and adduction of the arm. NERVE SUPPLY: Axillary nerve. ARTERIAL SUPPLY: Circumflex scapular artery and posterior circumflex humeral artery. CLINICAL: The tendon of this muscle is one of four that forms the rotator cuff of the shoulder joint. Repeated abduction and flexion can lead to wear and tear, causing injury or rupture of this cuff.

Posterior Muscles

- levator scapulae - rhomboid major - rhomboid minor - teres major

Deep Muscles of the Shoulder

- pectoralis minor - subclavius - levator scapulae - rhomboid major - rhomboid minor - teres major - serratus anterior - subscapularis - supraspinatus - infraspinatus - teres minor

Lateral Muscle

- serratus anterior - supraspinatus - infrapsinatus - subscapularis - teres minor

Rotator Cuff Muscles

- supraspinatus - infrapsinatus - subscapularis - teres minor

Pectoralis Minor

ORIGIN: 3rd to 5th ribs. INSERTION: Coracoid process of the scapula. ACTION: Pulls the scapula medially, forwards and downwards; aids in respiration. NERVE SUPPLY: Medial and lateral pectoral nerves (C6 - T1). ARTERIAL SUPPLY: Pectoral branch of the thoracoacromial artery; deltoid branch of thoracoacromial artery

Subclavius

ORIGIN: Costal cartilage and the 1st rib. INSERTION: Acromial end of the clavicle. ACTION: Draws the clavicle downward and forward; elevation of the 1st rib. NERVE SUPPLY: Subclavian nerve. ARTERIAL SUPPLY: Clavicular branch of the thoracoacromial artery.

Teres Major

ORIGIN: Dorsal surface of the inferior angle of the scapula. INSERTION: Crest of the lesser tubercle of the humerus. ACTION: Internal rotation, adduction and extension of the arm. NERVE SUPPLY: Subscapular nerve. ARTERIAL SUPPLY: Circumflex scapular artery; subscapular artery.

Infraspinatus

ORIGIN: Infraspinous fossa of the scapula. INSERTION: Greater tubercle of the humerus. ACTION: External rotation of the arm. NERVE SUPPLY: Suprascapular nerve (C4-C6). ARTERIAL SUPPLY: Circumflex scapular artery; suprascapular artery. CLINICAL: The tendon of this muscle is one of four that forms the rotator cuff of the shoulder joint. Repeated abduction and flexion can lead to wear and tear, causing injury or rupture of this cuff. Lesions of the suprascapular nerve can result in weak shoulder rotation and posterolateral shoulder pain.

Rhomboid Minor

ORIGIN: Spinous processes of the C7-T1 vertebrae and the inferior ligamentum nuchae. INSERTION: Medial margin of the scapula inferior to the spine. ACTION: Stabilization, retraction, elevation and internal rotation of the scapula. NERVE SUPPLY: Dorsal scapular nerve (C4-C5). ARTERIAL SUPPLY: Dorsal scapular artery.

Subscapularis

ORIGIN: Subscapular fossa of the scapula. INSERTION: Lesser tubercle of the humerus. ACTION: Internal rotation and extension of the arm. NERVE SUPPLY: Subscapular nerve. ARTERIAL SUPPLY: Subscapular artery. CLINICAL: The tendon of this muscle is one of four that forms the rotator cuff of the shoulder joint. Repeated abduction and flexion can lead to wear and tear, causing injury or rupture of this cuff.

Supraspinatus

ORIGIN: Supraspinous fossa of the scapula. INSERTION: Greater tubercle of the humerus. ACTION: Abduction of the arm. NERVE SUPPLY: Suprascapular nerve. ARTERIAL SUPPLY: Suprascapular artery. CLINICAL: The tendon of this muscle is one of four that forms the rotator cuff of the shoulder joint. Repeated abduction and flexion can lead to wear and tear, causing injury or rupture of this cuff.