Extrinsic Muscles

Superficial: Trapezius, Latissimus Dorsi

Deep Layers: Rhomboids, Levator Scapulae and Serratus Anterior

Main function:

The main function of the extrinsic muscles of the shoulder region is to attach the axial skeleton to the pectoral girdle and the humerus

Trapezius:

Action: elevate, depress, retract and laterally rotate the scapula

Elevation is provided by the upper fibres

Depression is provided by the lower fibres

Lateral Rotation if provided by upper and lower fibres

Innervation: This muscle is innervated by spinal accessory (Cranial Nerve XI)

Latissimus Dorsi:

Action: is to adduct, extend and medially rotate the arm, depress the scapula

Innervation: is provided by the thoracodorsal nerve coming from the posterior cord of the brachial plexus

Blood: Thoracodorsal vessels

Levator Scapulae and Rhomboids

Action: elevate and retract the scapula

Innervation: is provided by the dorsal scapular nerve (coming from the superior trunk of the brachial plexus and also the rhomboids is innervated by the cervical plexus)

Serratus Anterior

Action: some rotation, holds scapula against the thoracic wall, and protracts scapula

Innervation: long thoracic scapula (coming from c5 c6 c7 origins of ventral rami)

Category: Anatomy Notes