LigamentAttachmentsComment
Joint capsuleMargin of glenoid cavity → anatomical neck of humerusLoose fibrous capsule
Weakest inferiorly
GlenohumeralSupraglenoid tubercle → blend with fibrous capsule (superior, middle and inferior bands)Reinforce anterior capsule
CoracohumeralCoracoid process → greater tubercle of humerusStrong
Transverse humeralBridges intertubercular groove between greater and lesser tuberclesHolds tendon of biceps brachii in intertubercular groove
Coraco-acromialCoracoid process → acromionCompletes coraco-acromial arch protecting humeral head

 

MuscleProximal Attachment (Origin)Distal Attachment (Insertion)InnervationMain ActionsBlood Supply
TrapeziusSuperior nuchal line, external occipital protuberance, nuchal ligament, and spinous processes of C7–T12Lateral third of clavicle, acromion, spine of scapulaSpinal root of accessory nerve (CN XI) and C3 and C4Elevates, retracts, and rotates scapula; lower fibers depress scapulaTransverse cervical artery, dorsal perforating branches of posterior intercostal arteries
Latissimus dorsiSpinous processes of T7–L5, thoracolumbar fascia, iliac crest, and last three ribsHumerus (intertubercular sulcus)Thoracodorsal nerve (C6–C7)Extends, adducts, and medially rotates humerus at shoulderThoracodorsal artery, dorsal perforating branches of 9th, 10th, and 11th posterior intercostal, subcostal, and first three lumbar arteries

 

MuscleProximal Attachment (Origin)Distal Attachment (Insertion)InnervationMain ActionsBlood Supply
Levator scapulaePosterior tubercles of transverse processes of C1–C4Medial border of scapula from superior angle to spineVentral rami of C3–C4 and dorsal scapular nerveElevates scapula medially, inferiorly rotates glenoid cavityDorsal scapular artery, transverse cervical artery, ascending cervical artery
Rhomboid minorLigamentum nuchae, spines of C7 and T1 vertebraeMedial border of scapula above base of spine of scapulaDorsal scapular nerve (C4–C5)Fixes scapula to thoracic wall and retracts and rotates it to depress glenoid cavityDorsal scapular artery OR deep branch of transverse cervical artery, dorsal perforating branches of the upper five or six posterior intercostal arteries
Rhomboid majorSpinous processes of T2–T5 vertebraeMedial border of scapula below base of spine of scapulaDorsal scapular nerve (C4–C5)Fixes scapula to thoracic wall and retracts and rotates it to depress glenoid cavityDorsal scapular artery OR deep branch of transverse cervical artery, dorsal perforating branches of the upper five or six posterior intercostal arteries

 

 

MuscleProximal Attachment (Origin)Distal Attachment (Insertion)InnervationMain ActionsBlood Supply
DeltoidLateral third of anterior clavicle, lateral acromion, inferior edge of spine of scapulaDeltoid tuberosity of humerusAnterior and posterior branches of axillary nerve (C5,C6)Clavicular part: flexes and medially rotates arm; Acromial part: abducts arm beyond initial 15 degrees done by supraspinatus;Spinal part: extends and laterally rotates armPosterior circumflex humeral artery, deltoid branch of thoraco-acromial artery
SupraspinatusSupraspinous fossa of scapulaSuperior facet of greater tubercle of humerusSuprascapular nerve (C5,C6)Initiates arm abduction, acts with rotator cuff musclesSuprascapular artery
InfraspinatusInfraspinous fossa of scapula and deep fasciaMiddle facet of greater tubercle of humerusSuprascapular nerve (C5,C6)Lateral rotation of arm (with teres minor)Suprascapular artery
Teres minorUpper two thirds of posterior surface of lateral border of scapulaInferior facet of greater tubercle of humerusPosterior branch of axillary nerve (C5,C6)Laterally rotates armCircumflex scapular artery
Teres majorPosterior surface of inferior angle of scapulaMedial lip of intertubercular sulcus of humerusInferior subscapular nerve (C5,C6)Adducts and medially rotates armCircumflex scapular artery
SubscapularisSubscapular fossaLesser tubercle of humerusSuperior and inferior subscapular nerves (C5–C6)Medially rotates arm and adducts it; helps hold humeral head in glenoid cavitySubscapular artery, lateral thoracic artery