Triangles of the neck (overview)

The term triangles of the neck is used to describe divisions created by major muscles in the neck region.

The side of the neck presents a somewhat quadrilateral outline, limited by:

This space is subdivided into two large triangles by the sternocleidomastoid, which passes obliquely across the neck, from the sternum and clavicle below to the mastoid process of the temporal bone and the occipital bone above. 

The triangular space in front of the sternocleidomastoid muscle is called the anterior triangle of the neck; and the space behind it - the posterior triangle of the neck (also known as the lateral triangle of the neck).