Which muscle is responsible for neck movements and is connected to the collarbone?

The muscle responsible for neck movements and connected to the collarbone is the sternocleidomastoideus. This muscle plays a crucial role in various head and neck movements, such as rotation and flexion of the head. It is named for its origin at the sternum and clavicle (collarbone) and its insertion at the mastoid process of the temporal bone of the skull.

The sternocleidomastoideus enables actions like turning the head to the side or tilting it toward the shoulder, making it essential for many daily movements as well as in functions like looking around. Its anatomical positioning allows it to effectively coordinate these movements through its attachments to both the collarbone and the skull.

The other muscles listed, such as the platysma, sternohyoid, and trapezius, serve different functions and are involved in various other actions around the neck and shoulders, but they do not share the same specific connection and functional role in neck movement as the sternocleidomastoideus.