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Upper Extremities - Shoulder | Arm Wesson Pious A. Espiritu, MD, MHA, FPOA Cutaneous Innervation Supraclavicular artery - supplies the skin over the lateral end of the clavicle. Anterior and posterior circumflex humeral arteries - skin over deltoid. Musculocutaneous and fasciocutaneous perfor...

Upper Extremities - Shoulder | Arm Wesson Pious A. Espiritu, MD, MHA, FPOA Cutaneous Innervation Supraclavicular artery - supplies the skin over the lateral end of the clavicle. Anterior and posterior circumflex humeral arteries - skin over deltoid. Musculocutaneous and fasciocutaneous perforators - Supplies the area of the upper arm. Clavicle Articulates with the sternum and 1st costal cartilage medially and with the acromion process of the scapula laterally. Acts as a strut that holds the arm away from the trunk. The medial two thirds of the clavicle is convex forward and its lateral third is concave forward. Sternoclavicular joint This occurs between the sternal end of the clavicle, the manubrium sterni, and the 1st costal cartilage. Synovial plane joint Capsule surrounds the joint and is attached to the margins of the articular surfaces. Classification of joints Fibrous – bones connected by fibrous tissue. Cartilaginous – bones connected by cartilage. Synovial – articulating surfaces enclosed within fluid-filled joint capsule. Synovial joints Most common type of joint in the body Unlike fibrous or cartilaginous joints, the articulating bone surfaces at a synovial joint are not directly connected to each other with fibrous connective tissue or cartilage. The joint is surrounded by an articular capsule that defines a joint cavity filled with synovial fluid. Scapula Flat triangular bone that lies on the posterior chest wall between the 2nd and 7th ribs. The inferior angle of the scapula can be palpated easily in the living subject and marks the level of the 7th rib and the spine of the 7th thoracic vertebra. Glenohumeral joint Occurs between the rounded head of the humerus and the shallow, pear-shaped glenoid cavity of the scapula. Synovial ball-and-socket joint The capsule is thin and lax, allowing a wide range of movement. It is strengthened by fibrous slips from the tendons of the the rotator cuff muscles. Shoulder Ligaments Glenohumeral ligaments are three weak bands of fibrous tissue that strengthen the front of the capsule. Transverse humeral ligament strengthens the capsule and bridges the gap between the two tuberosities. Coracohumeral ligament strengthens the capsule above and stretches from the root of the coracoid process to the greater tuberosity of the humerus. Coracoacromial ligament extends between the coracoid process and the acromion. Its function is to protect the superior aspect of the joint. Shoulder dislocation Shoulder joint is the MC dislocated joint in the body. Anterior dislocation > Posterior dislocation. Axillary nerve is vulnerable to injury during anterior shoulder dislocation. Muscles connecting the scapula to the humerus: 1. Deltoid Origin: Lateral third of clavicle, acromion, spine of scapula Insertion: Humeral shaft Action: Anterior fibers - Flexes the arm Middle fiber - abducts the arm Posterior fiber - Extends the arm Nerve supply: Axillary nerve 2. Supraspinatus Origin: Supraspinous fossa of scapula Insertion: Greater tuberosity of humerus Action: Abducts the arm Nerve supply: Suprascapular nerve 3. Supraspinatus Origin: Infraspinous fossa of scapula Insertion: Greater tuberosity of humerus Action: External rotates the arm Nerve supply: Suprascapular nerve 3. Teres minor Origin: Upper two thirds of lateral border of scapula Insertion: Greater tuberosity of humerus Action: External rotates the arm Nerve supply: Axillary nerve 4. Subscapularis Origin: Subscapular fossa Insertion: Lesser tuberosity of humerus Action: Internal rotates the arm  Nerve supply: Subscapular nerve 5. Origin: Lower third of lateral border of scapula Insertion: Medial lip of bicipital groove Action: Internal rotates and adducts the arm Nerve supply: Subscapular nerve 6. Teres major Internal Rotator: Origin: Subscapularis – subscapular nerve Lower third of lateral border of scapula Insertion: Medial lip of bicipital groove Action: Internal rotates and adructs the arm Nerve supply: Subscapular nerve Rotator cuff muscles External rotators: Supraspinatus – Suprascapular nerve Infraspinatus - Suprascapular nerve Teres minor – Axillary nerve Humerus The humerus articulates with the scapula at the shoulder joint and with the radius and ulna at the elbow joint. The upper end of the humerus has a head that articulates with the glenoid cavity of the scapula. The lower end has the rounded capitulum for articulation with the head of the radius, and the pulley-shaped trochlea for articulation with the trochlear notch of the ulna. Radial fossa receives the head of the radius when the elbow is flexed. Coronoid fossa receives the coronoid process of the ulna when the elbow is flexed. Olecranon fossa receives the olecranon process of the ulna when the elbow joint is extended. Fascial compartment of the arm Anterior compartment Muscles Biceps brachii Coracobrachialis Brachialis Nerve supply Musculocutaneous nerve Blood supply Brachial artery Anterior compartment: 1. Biceps brachii Origin: Supraglenoid tubercle (Long head) Coracoid process (Short head) Insertion: Radial tuberosity and fascia of forearm via bicipital aponeurosis Action: Supinator of forearm and flexor of elbow joint. Nerve supply: Musculocutaneous nerve 2. Coracobrachialis Origin: Coracoid process Insertion: Humeral shaft (medial side) Action: Flexes arm and also weak adductor Nerve supply: Musculocutaneous nerve 3. Brachialis Origin: Distal half of anterior humeral shaft Insertion: Coronoid process of ulna Action: Elbow flexion Nerve supply: Musculocutaneous nerve Posterior compartment: 1. Triceps Origin: Lateral head : Upper half of posterior surface of shaft of humerus. Medial head : Lower half of posterior surface of shaft of humerus Long head : Infraglenoid tubercle of scapula Insertion: Olecranon process of ulna Action: Elbow extension Nerve supply: Radial nerve Elbow joint Occurs between the trochlea and capitulum of the humerus and the trochlear notch of the ulna and the head of the radius. Synovial hinge joint Blood and Nerve supply Axillary artery Begins at the lateral border of the 1st rib as a continuation of the subclavian artery. Ends at the lower border of the teres major muscle, where it continues as the brachial artery. Pectoralis minor muscle crosses in front of the axillary artery and divides it into three parts. Brachial artery Begins at the lower border of the teres major muscle as a continuation of the axillary artery. It terminates opposite the neck of the radius by dividing into the radial and ulnar arteries. Brachial plexus Formed by the union of the anterior rami of the 5th, 6th, 7th, and 8th cervical and the 1st thoracic spinal nerves. The plexus can be divided into roots, trunks, divisions, and cords.( ending with the terminal branches) Roots and trunks The roots of C5 and 6 unite to form the upper trunk. The root of C7 continues as the middle trunk. The roots of C8 and T1 unite to form the lower trunk. Divisions and cords The anterior divisions of the upper and middle trunks unite to form the lateral cord. The anterior division of the lower trunk continues as the medial cord. The posterior divisions of all three trunks join to form the posterior cord. Main branches Musculocutaneous nerve Axillary nerve Radial nerve Median nerve Ulnar nerve Musculocutaneous nerve Arises from the lateral cord of the brachial plexus. Nerve supply of Coracobrachialis, biceps brachii, brachialis muscles; supplies skin along lateral border of forearm when it becomes the lateral cutaneous nerve of forearm. Axillary nerve From the posterior cord of the brachial plexus. Supplies the deltoid and teres minor. Radial nerve Largest branch of the brachial plexus and lies behind the axillary artery. Supplies the posterior compartment of the arm and forearm. Median nerve From the medial and lateral cords of the brachial plexus. Supplies the anterior compartment of the forearm except FCU. Ulnar nerve From the medial cord of the brachial plexus.