Shoulder Muscles

Action: Adducts and medially rotates humerus; draws scapula anteriorly and inferiorly; acting alone, clavicular head flexes humerus and sternocostal head extends it from the flexed positionLateral Attachment: Lateral lip of intertubercular sulcus (groove) of humerusMedial Attachment: Clavicular head: anterior surface of medial half of clavicle Sternocostal head: anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique muscle

Action: Stabilizes scapula by drawing inferiorly and anteriorly against thoracic wallLateral Attachment: Medial boarder and superior surface of coracoid process of scapulaMedial Attachment: 3rd-5th ribs near their costal cartilages

Action: Anchors and depresses clavicleLateral Attachment: Inferior surface of middle third of clavicleMedial Attachment: Junction of 1st rib and its costal cartilage

Action: Protracts scapula and holds against thoracic wall; rotates scapula

Action: Descending (superior) part elevates; ascending (inferior) part depresses; and middle part (or all parts together) retracts scapula; descending and ascending parts act together to rotate glenoid cavity superiorlyLateral Attachment: Lateral third of clavicle; acromion and spine of scapulaMedial Attachment: Medial third of superior nuchal line; external occipital protuberance; nuchal ligament; spinous processes of C7-T12 vertebrae

Action: Extends, adducts, and medially rotates humerus; raises body toward arms during climbingLateral Attachment: Floor of intertubercular sulcus (groove) of humerusMedial Attachment: Spinous processes of inferior 6 thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3 or 4 ribs

Action: Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapulaLateral Attachment: Medial border of scapula superior to root of spineMedial Attachment: Posterior tubercles of transverse processes of C1-C4 vertebrae

Action: Retract scapula and rotate it to depress glenoid cavity; fix scapula to thoracic wallLateral Attachment: Minor: triangular area at medial end of scapular spine Major: medial border of scapula from level of spine to inferior angleMedial Attachment: Minor: nuchal ligament; spinous processes of C7 and T1 vertebrae Major: spinous processes of T2-T5 vertebrae

Action: Clavicular (anterior) part flexes and medially rotates arm; acromial (middle) part abducts arm; spinal (posterior) part extends and laterally rotates armDistal Attachment: Deltoid tuberosity of humerusProximal Attachment: Lateral third of clavicle; acromion and spine of scapula

Action: Initiates and assists deltoid in abduction of arm and acts with other rotator cuff musclesDistal Attachment: Superior facet of greater tubercle of humerusProximal Attachment: Supraspinous facia of scapula

Action: Laterally rotate arm; help hold humeral head in glenoid cavity of scapulaDistal Attachment: Middle Facet of greater tubercle of humerusProximal Attachment: Infraspinous fossa of scapula

Action: Laterally rotate arm; help hold humeral head in glenoid cavity of scapulaDistal Attachment: Inferior facet of greater tubercle of humerusProximal Attachment: Middle part of lateral border of scapula

Action: Adducts and medially rotates armDistal Attachment: Medial lip of intertubercular groove of humerusProximal Attachment: Prosterior surface of inferior angle of scapula

Action: Medially rotates and adducts arm; helps hold humeral head in glenoid cavityDistal Attachment: Lesser tubercle of humerusProximal Attachment: Subscapular fossa (most of anterior surface of scapula)