Trapezius Muscle

Definition

The trapezius muscle is a large, flat, triangular muscle located in the upper back and neck region. It plays a crucial role in the movement and stabilization of the shoulder blade and neck.

5 Must Know Facts For Your Next Test

1. The trapezius muscle is divided into three distinct parts: the upper, middle, and lower fibers, each with slightly different functions.
2. The upper trapezius fibers are responsible for shrugging the shoulders, while the middle fibers retract the shoulder blades, and the lower fibers depress the shoulder blades.
3. The trapezius muscle is innervated by the spinal accessory nerve (cranial nerve XI), which is assessed during the cranial nerve examination.
4. Weakness or dysfunction of the trapezius muscle can lead to impaired shoulder and neck movement, as well as postural abnormalities.
5. The trapezius muscle is often used as a landmark for identifying the location of the spinal accessory nerve during clinical examinations and procedures.

Review Questions

• Explain the role of the trapezius muscle in the cranial nerve exam.
  • During the cranial nerve exam, the function of the trapezius muscle is assessed as part of the evaluation of the spinal accessory nerve (cranial nerve XI). The examiner will observe the patient's ability to shrug their shoulders, which is a primary function of the upper trapezius fibers. Weakness or paralysis of the trapezius muscle may indicate a lesion or injury to the spinal accessory nerve, which innervates this muscle.
• Describe how the different parts of the trapezius muscle contribute to shoulder and neck movements.
  • The trapezius muscle is divided into three distinct parts, each with a specific function. The upper fibers are responsible for elevating the shoulder blade, the middle fibers retract the shoulder blades, and the lower fibers depress the shoulder blades. Together, these movements allow for a wide range of shoulder and neck motions, including shrugging the shoulders, rotating the head, and stabilizing the scapula during arm movements. The coordinated action of the trapezius muscle is essential for proper shoulder and neck function.
• Analyze the importance of the trapezius muscle as a landmark for identifying the spinal accessory nerve during clinical examinations and procedures.
  • The trapezius muscle is often used as a landmark for locating the spinal accessory nerve (cranial nerve XI) during clinical examinations and various medical procedures, such as nerve blocks or surgical interventions. The muscle's superficial location and its innervation by the spinal accessory nerve make it a reliable reference point for healthcare providers. Identifying the trapezius muscle can help guide the assessment of nerve function and facilitate targeted interventions involving the spinal accessory nerve, which is crucial for maintaining proper shoulder and neck mobility.

Related terms

Shoulder Blade: Also known as the scapula, the shoulder blade is a flat, triangular bone that provides attachment points for several muscles, including the trapezius.

Neck Muscles: The trapezius muscle works in conjunction with other neck muscles to control the movement and positioning of the head and neck.

Shoulder Elevation: The trapezius muscle is responsible for elevating the shoulder blade, a movement that is important for various arm and shoulder actions.