The sternocleidomastoid muscle flexes the neck and helps with the oblique rotation of the head. Also, the muscle helps in forced inspiration while breathing, and it raises the sternum. As for forced inspiration, the muscle also works in concert with the scalene muscles in the neck. The muscle originates at the medial portion of the collar bone. It inserts into the temporal bone's mastoid process near the ear and the base of the skull, and it stretches the entire length of the neck. Two nerves serve the sternocleidomastoid muscle. For motor functions, the muscle uses the accessory nerve. The cervical plexus nerve provides for sensory function, which includes proprioception. This sensory modality is purely internal, as it covers the inner workings of the body. For this muscle, proprioception involves becoming aware of pain and transmiting signals to the brain. Also, two arteries serve the sternocleidomastoid. Oxygenated blood arrives at the muscle via the occipital artery in the head and superior thyroid artery in the neck.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Sternocleidomastoid