The sternocleidomastoid muscle (SCM) is a prominent neck muscle, one of over 20 pairs influencing neck movement. It's easily felt under the skin and serves as a key anatomical landmark.
Anatomy and Function
The SCM, as its name suggests, originates from two points: the sternum (breastbone) and the clavicle (collarbone). It inserts into the mastoid process, a bony projection behind the ear. This dual origin contributes to its diverse functions:
- Head Rotation: Contracting one SCM rotates the head to the opposite side.
- Head Flexion: Contracting both SCMs flexes the neck, bringing the chin towards the chest.
- Head Extension (limited): From a flexed position, the SCM can assist in extending the head.
This muscle's dual innervation (from multiple nerves) allows for precise control over these movements.
Clinical Significance
The SCM's superficial location and functional importance make it relevant in various medical contexts:
- Torticollis: This condition, characterized by a twisted neck, often involves SCM involvement.
- Anatomical Landmark: Its prominence aids in locating other neck structures during examinations.
- Neuromuscular Disorders: SCM dysfunction can be a symptom of various neuromuscular diseases.
The SCM plays a vital role in head and neck movement and serves as a significant anatomical and clinical marker.