Boundaries and Subdivisions of Posterior Triangle of Neck
Definition: The posterior triangle of the neck is a triangular space on the lateral aspect of the neck, situated behind the sternocleidomastoid muscle.
Boundaries
| Boundary | Formed By |
|---|---|
| Anterior | Posterior border of sternocleidomastoid (SCM) |
| Posterior | Anterior border of trapezius |
| Base (inferior) | Middle one-third of clavicle |
| Apex | Meeting point of SCM and trapezius at superior nuchal line / external occipital protuberance |
| Roof | Investing layer of deep cervical fascia (covered by skin, superficial fascia, platysma) |
| Floor | Muscular — prevertebral layer of deep cervical fascia |
Subdivisions
The posterior triangle is divided into two smaller triangles by the inferior belly of omohyoid muscle, which crosses the triangle obliquely.
| Triangle | Also Called | Location |
|---|---|---|
| Occipital triangle | — | Upper (larger) part — above omohyoid |
| Subclavian triangle | Supraclavicular triangle | Lower (smaller) part — below omohyoid |
The omohyoid is enclosed in a fascial sling derived from the investing layer of deep cervical fascia, tethering it to the clavicle — this is why swallowing moves the neck musculature.
Surface Markings
- Triangle visible on lateral neck when head is turned to opposite side (SCM stands out)
- Base = clavicle; apex = occiput