Anterior Triangle
The anterior boundary is the midline of the neck (i.e., straight line running from the base of the chin above to the jugular notch of the sternum below). The posterior boundary is formed by the anterior border of the sternocleidomastoid muscle. The superior border is the bony inferior border of the mandible. For ease of description the anterior triangle of the neck is further divided into smaller component triangles.
- Anterior border of SCM
- Inferior border of the mandible
- Midline of the neck
Muscular Triangle
The muscular triangle occupies the anterior aspect of the neck below the hyoid bone. It is bounded by the superior belly of the omohyoid muscle, the sternocleidomastoid muscle, and the midline of the neck. It contains the infrahyoid strap muscles of the neck.
- Superior Omohyoid
- SCM
- Midline of neck
Submental Triangle
As the name implies, the submental triangle is below the chin (mens) and is bounded by the right and left anterior bellies of the digastric muscle and the body of the hyoid bone. The submental triangle is a midline structure. The other triangles are bilateral.
- Body of hyoid
- Anterior digastric (right / left)
Submandibular Triangle
The boundaries of the submandibular triangle are the inferior border of the mandible and the upper borders of the posterior and anterior bellies of the digastric muscle. This region contains the submandibular gland, submandibular lymph nodes, the lingual and facial arteries, cranial nerve XII, and the nerve to the mylohyoid muscle.
- Anterior digastric
- Posterior digastric
- Inferior border of the mandible
Carotid Triangle
The carotid triangle is bounded by the superior belly of the omohyoid muscle, the posterior belly of the digastric muscle, and the sternocleidomastoid muscle. It contains the common carotid artery and its branches; the internal jugular vein and its tributaries; cranial nerves X, XI, and XII; and several branches of the cervical plexus.
- Anterior border of SCM
- Superior omohyoid
- Posterior digastric
