Which muscle must be retracted to expose the thyroid gland during surgery?

The muscle that must be retracted to expose the thyroid gland during surgery is the sternocleidomastoid. This muscle is located at the front and sides of the neck and plays a significant role in the movement of the head and neck. When performing surgery in the cervical region, particularly thyroid surgery, it is necessary to retract the sternocleidomastoid muscle to gain proper access to the thyroid gland, which lies beneath it at the level of the lower neck.

Retracting the sternocleidomastoid allows surgeons to visualize the anatomy clearly, including the thyroid gland itself, the trachea, and surrounding structures. This is crucial for ensuring that the procedure can be performed safely and effectively, minimizing the risk of injury to vital structures such as the recurrent laryngeal nerve and the parathyroid glands. Other muscles like the trapezius, deltoid, and pectoralis major are located either further posteriorly or laterally and do not obstruct access to the thyroid gland in the midline of the neck.