SHOULDER REGION MUSCLES Coracobrachialis Adduction of the shoulder

SHOULDER REGION MUSCLES

Coracobrachialis Adduction of the shoulder & flexion.

Pectoralis Major The first action is flexion of the humerus, Secondly, it adducts the humerus. Thirdly, it rotates the humerus medially. Finally it aids in deep inspiration

Subscapularis Internal rotation of the shoulder

Deltoid Abduction of shoulder

Infraspinatus External rotation

Teres Major Adduction of scapula

Teres Minor The infraspinatus and teres minor attach to head of the humerus; as part of the rotator cuff they help hold the humeral head in the glenoid cavity of the scapula. They work in tandem with the posterior deltoid to externally (laterally) rotate the humerus, as well as perform transverse abduction, extension and transverse extension.

Supraspinatus Abduction of the shoulder

Coracobrachia lis Subscapularis Pect. Major Deltoid

Supraspinatus Infraspinatus Teres Major Teres Minor

Practice l l l List the muscles that do flexion of the shoulder Coracobrachialis Pectoralis major (upper to part) Anterior Deltoid Biceps • List the muscles that do extension of the shoulder • Latissimus dorsi • Teres major • Posterior deltoid • Pectoralis major (lower fibers to neutral)

Practice l l l List the muscles that do adduction of the shoulder Pectoralis major (lower and upper below 90°) Coracobrachialis Latissimus dorsi Teres major List the muscles that do abduction of the shoulder • Deltoid (all sections) • Supraspinatus • Pectoralis major (upper past 90°)

Practice l l l List the muscles that do internal rotation of the shoulder Subscapularis Latissimus dorsi Teres major Anterior deltoid Pect. major • List the muscles that do external rotation of the shoulder • Infraspinatus • Teres minor • Posterior deltoid

Questions l l l l l What muscle works closely with the anterior deltoid? Pectoralis major What muscle is involved in any lifting movements? Deltoid What is the major (strongest) extensor muscle? Latissimus Dorsi Name the four rotator cuff muscles. Subscapularis, Supraspinatus, Infraspinatus, and Teres minor. What muscle works closely with the infraspinatus? Teres minor

AXILLARY REGION

The axilla, or armpit, is a pyramidshaped space between the upper part of the arm and the side of the chest. Realize that the upper end, or apex, is directed into the root of the neck and is bounded anteriorly by the clavicle, posteriorly by the upper border of the scapula, and medially by the outer border of the first rib. The lower end, or base, is bounded anteriorly by the anterior axillary fold (formed by the lower border of the pectoralis major muscle), behind by the posterior axillary fold (formed by the tend of latissimus dorsi and the teres major muscle), and medially by the chest wall.

Walls of the Axilla. Identify the structures forming the walls of the axilla:

Anterior wall. This is formed by the pectoralis major, pectoralis minor, clavipectoral fascia, and subclavius muscle

Posterior wall. From above downward this wall is formed by the subscapularis, latissimus dorsi, and the teres major muscles.

Medial wall. This is formed by the upper four or five ribs and the intercostal spaces covered by the serratus anterior muscle.

Lateral wall. This is formed by the coracobrachialis and biceps muscles in the bicipital groove of the humerus.

Axillary Sheath. The axillary artery (but not the vein) and the brachial plexus are enclosed in a fascial sheath derived from the prevertebral layer of deep cervical fascia in the neck.

Axillary Artery. This commences at the outer border of the first rib as a continuation of the subclavian artery. Having passed through the axilla, it becomes the brachial artery at the lower border of the teres major muscle. It is arbitrarily divided into three parts by the pectoralis minor muscle that crosses it anteriorly.

Brachial Plexus.

Brachial plexus The brachial plexus is divided into Roots, Trunks, Divisions, Cords, and Branches. There are five "terminal" branches and numerous other "pre-terminal" or "collateral" branches that leave the plexus at various points along its length. l The five roots are the five anterior rami of the spinal nerves, after they have given off their segmental supply to the muscles of the neck. l These roots merge to form three trunks: – "superior" or "upper" (C 5 -C 6) – "middle" (C 7) – "inferior" or "lower" (C 8 -T 1) l

Brachial plexus Each trunk then splits in two, to form six divisions: – anterior divisions of the upper, middle, and lower trunks – posterior divisions of the upper, middle, and lower trunks l These six divisions will regroup to become three cords. The cords are named by their position with respect to the axillary artery. – The posterior cord is formed from the three posterior divisions of the trunks (C 5 -T 1) – The lateral cord is the anterior divisions from the upper and middle trunks (C 5 -C 7) – The medial cord is simply a continuation of the anterior division of the lower trunk (C 8 -T 1) l The branches are shown in the following diagram l

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