Introduction - the neck is divided by the sternocleidomastoid into the. Because the location and contents of the posterior triangle were discussed earlier in the course, we will now discuss the anterior triangle. The boundaries of the anterior triangle are the anterior border of sternocleidomastoid, lower border of mandible and midline of the neck. Subunit triangles are named either for their location or contents. Using the hyoid bone as a dividing line, above it are the submental and submandibular triangles; below it are the carotid and muscular triangles. 2) hyoid bone - at c3 level thyroid cartilage and in particular, the laryngeal b. c. prominence, This re-establishes air flow to lungs, e. g. , in presence of laryngeal spasm, because the cricothyroid membrane lies inferior to the larynx. We are most interested in observing aspects of the continuity among various areas, i. e. , thorax, upper limb and head.