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Shoulder Muscles
Origin, Insertion, Innervation, Action of Shoulder Muscles
Question | Answer |
---|---|
Deltoid | O: Lateral one third of the clavicle, acromion and spine of the scapula I: Deltoid tuberosity of the humerus N: Axillary C5,6 |
Teres Major | O: Inferior angle and lower one-third of lateral border of scapula I: Crest of the lesser tubercle of the humerus N: Lower subscapular C5, 6, 7 |
Supraspinatus | O: Supraspinous fossa of scapula I: Greater tubercle of humerus N: Suprascapular C4, 5, 6 |
Infraspinatus | O: Infraspinous fossa of scapula I: Greater tubercle of humerus N: Suprascapula C(4), 5, 6 |
Teres Minor | O: Upper 2/3 of lateral border of the scapula I: Greater tubercle of humerus N: Axillary C5, 6 |
Subscapularis | O: Subscapular fossa I: Lesser tubercle of humerus N: Upper and lower subscapularis C5, 6, 7 |
Serratus Anterior | O: External surfaces of upper eight or nine ribs I: Anterior surface of medial border of the scapula N: Long thoracic C5, 6, 7, 8 |
Pectoralis Major | O: Medial 1/2 of clavicle, sternum and cartilage of 1st to 6th ribs I: Crest of greater tubercle of humerus N: Lateral pectoral C5, 6, 7 (Upper fibers) Lateral and medial pectoral C6, 7, 8, T1 (Lower fibers) |
Pectoralis Minor | O: 3rd, 4th, 6th ribs I: Medial surface of the coracoid process of the scapula N: Medial pectoral, with fibers from a communicating branch of lateral pectoral C(6), 7, 8, T1 |
Subclavius | O: First rib and cartilage I: Inferior surface of middle one third of clavicle N: subclavian C5, 6 |
Biceps Brachii | O: Coracoid process of scapula (short head) Supraglenoid tubercle of scapula (long head) I: Tuberosity of the radius and aponeurosis of biceps brachii N: Musculocutaneous C5, 6 |
All Fibers of the Deltoid Action | Abduct the shoulder |
Anterior Fibers of the Deltoid Action | Flex the shoulder Medially Rotate the shoulder Horizontally adduct the shoulder |
Posterior Fibers of the Deltoid Action | Extend the Shoulder Laterally Rotate the shoulder Horizontally abduct the shoulder |
Teres Major Action | Extend the shoulder Adduct the shoulder Medially rotate the shoulder |
Supraspinatus Action | Abduct the shoulder Stabilize the head of the humerus in the glenoid cavity |
Infraspinatus Action | Laterally rotate the shoulder Adduct the shoulder Stabilize the head of humerus in glenoid cavity |
Teres Minor Action | Laterally rotate the shoulder Adduct the shoulder Stabilize the head of the humerus in the glenoid cavity |
Subscapularis Action | Medially rotate the shoulder Stabilize the head of the humerus in the glenoid cavity |
Serratus Anterior Action | Abduct the scapula Upwardly rotate the scapula Depress the scapula Hold the medial border of the scapula against the rib cage (May act to elevate thorax during forced inhalation) |
All Fibers Pectoralis Major Action | Adduct the shoulder Medially rotate the shoulder Assist to elevate the thorax during forced inhalation (with arm fixed) |
Upper Fibers Pectoralis Major Action | Flex the shoulder Horizontally adduct the shoulder |
Lower Fibers Pectoralis Major Action | Extend the shoulder |
Pectoralis Minor Action | Depress the scapula Abduct the scapula Downwardly rotate the scapula (assist to elevate the thorax during forced inhalation with scapula fixed) |
Subclavius Action | Depress the clavicle and draw it anteriorly Elevate the first rib (to assist during inhalation) Stabilize the sternoclavicular joint |
Biceps Brachii Action | Flex the elbow Supinate the forearm Flex the shoulder |
Triceps Brachii Action | Extend the elbow Long Head Extends and adducts the shoulder |