What are the extrinsic shoulder muscles and what do they do?

The extrinsic shoulder muscles connect the upper limb to the axial skeleton (vertebral column, skull, and thorax). They control large-scale movements of the scapula and humerus, including elevation, depression, rotation, and stabilization of the shoulder girdle.

What are the main actions of the trapezius muscle?

The trapezius has multiple actions based on its fibers: upper fibers elevate the scapula (shoulder shrug), middle fibers retract (adduct) the scapula, lower fibers depress the scapula, and upper and lower fibers together rotate the scapula upward for overhead arm movement.

Why is the latissimus dorsi called the 'swimmer's muscle'?

The latissimus dorsi is called the 'swimmer's muscle' because it assists in extending, adducting, and medially rotating the humerus, which are key movements for swimming strokes and climbing activities.

What happens if the spinal accessory nerve is injured?

Injury to the spinal accessory nerve (CN XI) affects the trapezius, leading to shoulder droop, difficulty elevating the scapula, and an inability to raise the arm above horizontal due to loss of scapular rotation.

How do the rhomboid muscles function in the shoulder?

The rhomboid minor and major muscles primarily retract and stabilize the scapula against the thoracic wall. The rhomboid major also assists in elevating the scapula, helping maintain posture during arm movements.

What is the role of the subclavius muscle?

The subclavius is a small muscle that depresses and stabilizes the clavicle during shoulder movements. It also protects the underlying subclavian vessels and brachial plexus from compression.

What are the nerve supplies for the extrinsic shoulder muscles?

Key nerve supplies include: trapezius by the spinal accessory nerve (CN XI), latissimus dorsi by the thoracodorsal nerve (C6–C8), levator scapulae and rhomboids by the dorsal scapular nerve (C5), and subclavius by the nerve to subclavius (C5–C6).

Extrinsic Shoulder Muscles – Trapezius, Latissimus & More

❓ Frequently Asked Questions