The posterior scalene is a muscle located in the neck, part of the group known as the scalene muscles. It is situated behind the anterior and middle scalene muscles and plays a role in the movement of the neck and the elevation of the second rib during breathing. This muscle originates from the cervical vertebrae and inserts into the second rib. It is innervated by the cervical spinal nerves and is important for maintaining proper posture and facilitating respiratory function, particularly during deep inhalation. Understanding the posterior scalene can help in diagnosing neck and respiratory issues.