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Trapezius

Origin: Medial superior nuchal line and external protuberance of the occipital line, ligamentum nuchae and spinous processes on C7- T12.

Insertion: Lateral clavicle, acromion and spine of scapula.

Actions:

Upper fibres: Elevate and upwardly rotate scapula.

Mid fibres: Retract scapula.

Lower Fibres: Depress scapula.

Innervation: C3, C4 and accessory cranial nerve (XI).

Daily uses: Shrugging shoulders.

Other muscles …

Supraspinatus

Origin: Supraspinous fossa

Insertion: Greater tuberosity of the humerus

Actions: Abduction  Stabilisation of the humerus

Innervation: Suprascapular nerve

Daily uses: Holding shopping bags away from the body

Origin: Mid section of the lateral border of the scapula

Insertion: Greater tuberosity on the humerus

Actions:External rotation,  Shoulder adduction

Innervation: Axillary nerve

Daily uses: Brushing hair

Origin: Anterior (costal) surface of the scapula

Insertion: Lesser tuberosity of the humerus

Actions: Internal rotation , Adduction

Innervation: Upper and lower subscapular nerves

Daily uses: Tucking the back of your shirt into your trousers