Muscle groups

Shoulder

Deltoid

The origin of the deltoid is at the clavicle.

The insertion of this muscle is at the lateral surface of the humerus.

The joint action occurs when the anterior fibres flex the shoulder and assist in horizontal flextion and medial rotation.

Pectoralis major

Origin - Clavical, sternum and cartilages of ribs from 1-6.

Insertion - Top of the humerus.

The joint crossed - Glenohumeral.

Joint actions - Shoulder horizontal flextion

- Shoulder adduction

- Shoulder medial rotation

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Latissimus dorsi

Origin - thoracolumbar

Insertion - Top of the humerus

Joint crossed - Shoulder joint

Joint action - Origin fixed: adducts and extends the arm

Insertion fixed: tilts the pelvis forwards

Teres Major

Origin - Lateral border of the scapula near the inferior angle

Insertion - Humerus

Joint crossed - Shoulder joint

Joint action - Medial rotation, adduction and extension of the shoulder