The anterior triangle of the neck is divided into four smaller triangles by muscles and bones. It contains many important structures including muscles, blood vessels and nerves. The muscles are classified as suprahyoid or infrahyoid based on their position relative to the hyoid bone. The common carotid arteries and internal jugular vein pass through, supplying and draining structures of the head and neck. Several cranial and peripheral nerves also pass through, innervating areas within the triangles.

1. Anterior triangle of the neck

2. The anterior triangle of the neck is outlined by the
• Anterior border of the sternocleidomastoid muscle laterally,
• The inferior border of the mandible superiorly,
• The midline of the neck medially

5. It is further subdivided into several smaller triangles as follows:
1. The submandibular triangle is outlined by the inferior border of the mandible
superiorly and the anterior and posterior bellies of the digastric muscle inferiorly;
2. The submental triangle is outlined by the hyoid bone inferiorly, the anterior
belly of the digastric muscle laterally, and the midline;
3. The muscular triangle is outlined by the hyoid bone superiorly, the superior
belly of the omohyoid muscle, and the anterior border of the
sternocleidomastoid muscle laterally, and the midline;
4. The carotid triangle is outlined by the superior belly of the omohyoid muscle
anteroinferiorly, the stylohyoid muscle and posterior belly of the digastric
superiorly, and the anterior border of the sternocleidomastoid muscle
posteriorly.

6. • Each of these triangles contains numerous structures that can
be identified as being within a specific triangle, passing into a
specific triangle from outside the area, originating in one
triangle and passing to another triangle, or passing through
several triangles while passing through the region.
• A discussion of the anterior triangle of the neck must
therefore combine a systemic approach, describing the
muscles, vessels, and nerves in the area, with a regional
approach, describing the contents of each triangle.

7. Muscles
• The muscles in the anterior triangle of the neck
can be grouped according to their location
relative to the hyoid bone:
• muscles superior to the hyoid are classified as
suprahyoid muscles and include the stylohyoid,
digastric, mylohyoid, and geniohyoid;
• muscles inferior to the hyoid are infrahyoid
muscles and include the omohyoid, sternohyoid,
thyrohyoid, and sternothyroid.

11. Vessels
• Passing through the anterior triangle of the
neck are the common carotid arteries and
their branches, the external and internal
carotid arteries. These vessels supply all
structures of the head and neck.
• Associated with this arterial system are the
internal jugular vein and its tributaries. These
vessels receive blood from all structures of the
head and neck.

12. Nerves
• Numerous cranial and peripheral nerves: pass through the
anterior triangle of the neck as they continue to their final
destination;
• send branches to structures in or forming boundaries of the
anterior triangle of the neck;
• while in the anterior triangle of the neck, send branches to
nearby structures.
• The cranial nerves in these categories include the facial
[VII], glossopharyngeal [IX], vagus [X], accessory [XI], and
hypoglossal [XII].
• The peripheral nerves in these categories include the
transverse cervical nerve from the cervical plexus and the
upper and lower roots of the ansa cervicalis.