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Muscles of the shoulder region

Muscles of the shoulder region: Are divided into Superficial muscles (Trapezius and Latissimus dorsi), that cover most of the other muscles on the back. Deep extrinsic muscles: arise from the axial skeleton ( Levator scapulae, Rhomboideus major and minor, and the serratus anterior). Intrinsic muscles arising from the scapula and passing to the humerus (arising and inserted on the skeleton of the limb): Deltoid, supraspinatus, infraspinatus, teres major and minor, and the subscapularis.

Trapezius muscle: it is somewhat triangular in shape, arises from occipital bone, ligamentum nuchae, spine of 7th cervical vertebra, spines of all thoracic vertebrae. Insertion: Upper fibers into lateral third of clavicle; middle and lower fibers into acromion and spine of scapula.
Muscles of the shoulder region

Trapezius muscle

Muscles of the shoulder region


Trapezius muscle: Nerve supply: spinal part of accessory nerve (XI cranial nerve). Function: Upper fibers elevate the scapula; middle fibers pull scapula medially; lower fibers pull medial border of scapula downward
Muscles of the shoulder region


Muscles of the shoulder region: Latissimus dorsi muscle: it arises from Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower three or four ribs, and inferior angle of scapula.


Muscles of the shoulder region: Latissimus dorsi muscle: Insertion: Floor of bicipital groove of humerus. Nerve supply: Thoracodorsal nerve. Function: Extends, adducts, and medially rotates the arm


Muscles of the shoulder region: Levator scapulae muscle: it arises from Transverse processes of 1st four cervical vertebrae. It inserts into the medial border of scapula. Nerve supply: dorsal scapular nerve Function: Raises medial border of scapula.

Levator scapulae muscle

Muscles of the shoulder region: Rhomboid major: it is flat muscle arises from second to 5th thoracic spines. It is inserted on medial border of scapula. Nerve supply: Dorsal scapular nerve. Function: Raises medial border of scapula upward and medially.

Rhomboid major

Muscles of the shoulder region: Rhomboid minor: it is flat muscle lies deep to the trapezius muscle. It arises from Transverse processes of 1st four cervical vertebrae. It inserts into medial border of scapula. Nerve supply: dorsal scapular nerve. Function: Raises medial border of scapula

Rhomboid minor

Muscles of the shoulder region: Serratus anterior : it covers much of the lateral aspect of the thorax. It arises from Upper eight ribs. It inserts into medial border and inferior angle of scapula. Nerve supply: Long thoracic nerve. Function: Draws forward (protracts) the scapula, hold the medial border of scapula firmly against the thoracic wall, and rotates scapula.

Serratus anterior :

Muscles of the shoulder region: Deltoideus (Deltoid muscle): is a large, thick, triangular muscle, which covers the shoulder joint in front, behind, and laterally. It arises from the lateral third of clavicle, acromion and spine of scapula.

Muscles of the shoulder region: Deltoideus (Deltoid muscle): Insertion: deltoid tuberosity on the middle of lateral surface of shaft of humerus. Nerve supply: axillary nerve. Function: abducts arm; anterior fibers flex and medially rotate arm; posterior fibers extend and laterally rotate arm.

Muscles of the shoulder region: Supraspinatus: occupies the whole of the supraspinous fossa of the scapula. It arises from the supraspinous fossa. It inserts into the greater tuberosity of humerus and capsule of the shoulder joint. Nerve supply: suprascapular nerve. Function: abducts the arm and stabilizes the shoulder joint.

Supraspinatus muscle

Muscles of the shoulder region: Infraspinatus: is a thick triangular muscle, occupies most of the infraspinous fossa of scapula. It arises from the infraspinous fossa. Insertion: greater tuberosity of humerus and the capsule of the shoulder joint. Nerve supply: Suprascapular nerve. Function: laterally rotates arm and stabilizes shoulder joint.

Infraspinatus

Muscles of the shoulder region: Teres minor: is a narrow, elongated muscle. Origin: upper two thirds of lateral border of scapula. It is inserted on greater tuberosity of humerus and capsule of the shoulder joint. Nerve supply: axillary nerve. Function: laterally rotates arm and stabilizes shoulder joint.


Teres minor


Muscles of the shoulder region: Teres major: is a thick but somewhat flattened muscle. It arises from lower third of lateral border of scapula and inserts into medial lip of bicipital groove of humerus. Nerve supply: lower subscapular nerve. Function: medially rotates and adducts arm and stabilizes shoulder joint.

Teres major

Muscles of the shoulder region: Subscapularis: is a large triangular muscle which fills the subscapular fossa of scapula. Origin: Subscapular fossa. Insertion: lesser tuberosity of humerus. Nerve supply: upper and lower subscapular nerves. Function: medially rotates and stabilizes shoulder joint.

Muscles of the shoulder region: The position and stability of the scapula on the posterior wall of the thorax is maintained by the tone and balance of the muscles attached to it. If one of these muscles is paralyzed, the balance is disturbed, as in dropped shoulder, caused by paralysis of the trapezius, or winged scapula, caused by paralysis of the serratus anterior.

Rotator Cuff

The rotator cuff is the name given to the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles, which are fused to the underlying capsule of the shoulder joint. This cuff plays a very important role in stabilizing the shoulder joint. The tone of these muscles assists in holding the head of the humerus in the glenoid cavity of the scapula during movements at the shoulder joint.

Rotator Cuff

The cuff lies on the anterior, superior, and posterior aspects of the joint. The cuff is deficient inferiorly, and this is a site of potential weakness.

Arterial Anastomosis around the Shoulder Joint

The extreme mobility of the shoulder joint may result in kinking of the axillary artery and a temporary occlusion of its lumen. To compensate for this, an important arterial anastomosis exists between the branches of the subclavian artery and the axillary artery, thus ensuring that an adequate blood flow takes place into the upper limb irrespective of the position of the arm.

Arterial Anastomosis around the Shoulder Joint

Branches from the Subclavian Artery:■ Suprascapular artery: distributed to the supraspinous and infraspinous fossae.■ Superficial cervical artery: gives off a deep branch that runs down the medial border of the scapula

Arterial Anastomosis around the Shoulder Joint

Branches from the Axillary Artery:■ Subscapular artery: and its circumflex scapular branch supply the subscapular and infraspinous fossae, respectively.■ Anterior and posterior circumflex humeral artery. Both the circumflex arteries form an anastomosing circle around the surgical neck of the humerus.

Joints of the Pectoral and Shoulder Region

Acromioclavicular Joint
It is an articulation between the acromion process of the scapula and the lateral end of the clavicle. It is synovial plane joint. There is capsule surrounds the joint and is attached to the margins of the articular surfaces.

Acromioclavicular Joint

The capsule is lined by the synovial membrane. The capsule is reinforced by Superior and inferior acromioclavicular ligaments. From the capsule, a wedge-shaped fibrocartilaginous disc projects into the joint cavity from above.

Acromioclavicular Joint

Coracoclavicular ligament: is an accessory ligament, it is very strong ligament extends from the coracoid process to the undersurface of the clavicle. It is largely responsible for stability of the clavicle and AC joint. Nerve supply: suprascapular nerve.

Acromioclavicular Joint

Movements: A gliding movement takes place when the scapula rotates or when the clavicle is elevated or depressed. Although it is small movement, but it is necessary to movement of the shoulder.