![]() The extensors are the triceps brachii and anconeus. ![]() The forearm flexors include the biceps brachii, brachialis, and brachioradialis. The forearm, made of the radius and ulna bones, has four main types of action at the hinge of the elbow joint: flexion, extension, pronation, and supination. When baseball pitchers undergo shoulder surgery it is usually on the rotator cuff, which becomes pinched and inflamed, and may tear away from the bone due to the repetitive motion of bring the arm overhead to throw a fast pitch. The tendons of the deep subscapularis, supraspinatus, infraspinatus, and teres minor connect the scapula to the humerus, forming the rotator cuff (musculotendinous cuff), the circle of tendons around the shoulder joint. Finally, the coracobrachialis flexes and adducts the arm. ![]() The long teres minor laterally rotates and extends the arm. The thick and flat teres major is inferior to the teres minor and extends the arm, and assists in adduction and medial rotation of it. Named for their locations, the supraspinatus (superior to the spine of the scapula) and the infraspinatus (inferior to the spine of the scapula) abduct the arm, and laterally rotate the arm, respectively. The subscapularis originates on the anterior scapula and medially rotates the arm. The deltoid, the thick muscle that creates the rounded lines of the shoulder is the major abductor of the arm, but it also facilitates flexing and medial rotation, as well as extension and lateral rotation. The anatomical and ligamental structure of the shoulder joint and the arrangements of the muscles covering it, allows the arm to carry out different types of movements. The rest of the shoulder muscles originate on the scapula. Stabilizes scapula during pectoral girdle movementĬervical and thoracic vertebrae (C7 and T1) Scapula: rotests inferiorly, retracts, elevates, and depresses spine: extends Muscle slips from certain ribs (1–8 or 1–9)Īnterior surface of vertebral border of scapulaĮlevates shoulders (shrugging) pulls shoulder blades together tilts head backwards Moves arm from side of body to front of body assists with inhalation Rotates shoulder anteriorly (throwing motion) assists with inhalationĪnterior surfaces of certain ribs (2–4 or 3–5) Stabilizes clavicle during movement by depressing it Muscles that Position the Pectoral Girdle Note that the pectoralis major and deltoid, which move the humerus, are cut here to show the deeper positioning muscles. The muscles that stabilize the pectoral girdle make it a steady base on which other muscles can move the arm.
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