Sternocleidomastoid at a glance
- What it is
- A thick superficial neck muscle forming the main landmark dividing the anterior and posterior triangles.
- Location
- Originates from the manubrium (sternal head) and medial third of the clavicle (clavicular head) and inserts onto the mastoid process and lateral part of the superior nuchal line.
- Function
- One side tilts the head to the same side and rotates the face to the opposite side; both together flex the neck and extend the head.
- Body system
- Muscular · paired (left and right)
- FMA ID
- FMA13409 (Foundational Model of Anatomy)
Key facts
- Innervation: spinal accessory nerve (CN XI), with proprioceptive fibers from C2–C3
- Blood supply: occipital and superior thyroid arteries
- The spinal accessory nerve crosses the posterior triangle from its posterior border to trapezius, superficially, where it is easily injured.
Clinical relevance
Shortening or fibrosis causes congenital torticollis.
Structures next to the sternocleidomastoid
The nearest named structures in the 3D model, measured from the centre of each part:
- Scalenus medius · muscular
- Lateral crico-arytenoid · muscular
- Oblique part of cricothyroid · muscular
- Thyrohyoid · respiratory
- Posterior crico-arytenoid · muscular
- Inferior pharyngeal constrictor · muscular
- Vertical intermediate part of longus colli · muscular
- Scalenus anterior · muscular
- Arytenoid cartilage · respiratory
- Straight part of cricothyroid · muscular
References
- Foundational Model of Anatomy: Sternocleidomastoid (FMA13409). EMBL-EBI Ontology Lookup Service.
- OpenStax. Anatomy and Physiology 2e, §11.2 Naming Skeletal Muscles. Rice University, 2022.
- Mitsuhashi N. et al. (2009). BodyParts3D: 3D structure database for anatomical concepts. Nucleic Acids Research 37, D782–D785. Data © The Database Center for Life Science, CC BY 4.0.
Related anatomy
Explore the whole body in the interactive 3D human anatomy model, or browse the A–Z list of human structures.