Limits. The neck is limited from the head by the line passing along the inferior margin of mandible, the apex of the mastoid process, the superior nuchal line and exterior occipital tuber.
The neck is limited from the thoracic cage, upper limb and back by the jugular notch of sternum, clavicle and the line drawn from the acromion to the spinous process of the VII cervical vertebra (C VII).
There are four regions of neck: anterior, sternocleidomastoid, lateral and posterior. The limits of the regions are found by surface landmarks: the inferior margin of the mandible, the anterior and posterior borders of the sternocleidomastoid muscle, the anterior border of the trapezius muscle, the jugular notch, and the clavicle (fig. 5.1).
The anterior region is limited superiorly by the inferior margin of mandible and by the chin; inferiorly - by the jugular notch of sternum; from the flanks - by the medial (anterior) borders of the m. sternocleidomastoideus. Within the anterior region, by palpating the hyoid bone, two parts are found: the suprahyoid, pars suprahyoidea, and the infrahyoid, pars infrahyoidea. Each of them in its turn consists of several triangles of the neck that are constructed with the help of projections of two more muscles: the digastric and omohyoid ones.
The anterior belly of the digastric muscle is projected from the middle of the inferior margin of chin up to the lateral surface of the hyoid bone; the posterior one - from the hyoid bone up to the mastoid process of the temporal bone. The projection of m. digastricus makes it possible to identify two triangles in the suprahyoid part: the submandibular (paired) and the submental (unpaired).
The submandibular triangle has the following sides: superiorly - the inferior margin of mandible (the base of the triangle); anteriorly - the anterior belly of the m. di-gastricus; posteriorly - its posterior belly. The submental triangle is situated between the left and right anterior bellies of the digastric muscle and the hyoid bone (the base of the triangle).