Trapezius

About

The trapezius muscle is a large, superficial muscle in the back that plays a crucial role in stabilizing and rotating the scapula. It extends from the external occipital protuberance and the superior nuchal line of the occipital bone, down to the spinous processes of the thoracic vertebrae. The muscle is divided into three parts: the descending (superior), transverse (middle), and ascending (inferior) parts. Each part has distinct functions, such as elevating, retracting, and depressing the scapula. The trapezius muscle inserts into the clavicle, acromion, and spine of the scapula. Its actions include scapular elevation, retraction, and depression, as well as neck extension and rotation. The muscle is innervated by the spinal accessory nerve (cranial nerve XI) and the anterior rami of spinal nerves C3 and C4. Its dysfunction can lead to issues like scapular winging, often due to nerve damage. Overall, the trapezius is essential for shoulder movements and posture, making it a key component of the upper limb musculature.