The primary shoulder neck muscle is called the trapezius.
The trapezius is a large, superficial muscle that extends from the base of the skull down the spine to the mid-back (thoracic spine) and out to the shoulder blade. It's essentially a kite-shaped muscle formed by two halves on either side of the spine.
Here's a breakdown of the trapezius and other muscles that contribute to shoulder and neck movement and stability:
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Trapezius: This muscle has three main sections (upper, middle, and lower fibers) which allow for a variety of movements including:
- Elevating the shoulder blades (shrugging)
- Retracting the shoulder blades (squeezing them together)
- Depressing the shoulder blades (pulling them downwards)
- Rotating the shoulder blades (tilting the shoulder)
- Extending the neck
- Laterally flexing the neck
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Levator Scapulae: This muscle runs from the cervical vertebrae to the superior angle of the scapula (shoulder blade). It primarily elevates the scapula and helps with neck rotation and lateral flexion.
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Sternocleidomastoid (SCM): While primarily a neck muscle, the SCM significantly impacts shoulder and head posture, and indirectly influences the shoulder joint's functionality. It connects the sternum and clavicle to the mastoid process of the skull. Actions include:
- Flexing the neck
- Rotating the head to the opposite side
- Lateral flexion of the neck
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Other Supporting Muscles: Many other muscles indirectly support shoulder and neck function, including the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis), deltoids, rhomboids, and various back muscles. These muscles provide stability and control during movement.
Therefore, while other muscles contribute, the most prominent muscle directly connecting the neck and shoulder is the trapezius.
