ABSTRACT
The neck comprises the distance between the mylohyoid muscle superiorly and the first rib inferiorly. The mylohyoid muscle forms the boundary between the floor of the mouth and the neck. By dividing the neck into triangular components, one can understand and locate the various structures in specific parts of the neck. The sternocleidomastoid (SCM) muscle separates the posterior triangle from the anterior triangle of the neck (Fig. 1). The superior attachment of this large muscle is the mastoid process, which is located immediately posterior to the external ear (auricle). The SCM then courses anteriorly and inferiorly to its attachment on the clavicle and the
sternum (8,9). The anterior triangles meet in the midline with the body of the mandible superiorly, the midline of the neck medially, and the SCM muscles posteriorly. The anterior triangle of the neck can be further subdivided into submental and submandibular triangles. The submental triangle is inferior to the anterior belly of the digastric muscle and superior to the hyoid bone and the midline of the neck with the floor formed by the mylohyoid muscle. The triangle is most noted for the presence of several submental lymph nodes that drain the floor of the oral cavity, tip of the tongue, and lower lip. The submandibular (digastric) triangle is located between the posterior and the anterior bellies of the digastric muscle and the inferior border of the mandible with its floor formed by the mylohyoid, hyoglossus, and middle constrictor muscles. The posterior triangle is bordered by the SCM muscle anteriorly, the trapezius muscle posteriorly, the deep cervical fascia superiorly, and the clavicle inferiorly.
