| Muscular triangle | |
|---|---|
 Muscular triangle | |
 Side of neck, showing chief surface markings. (Nerves are yellow, arteries are red.) | |
| Details | |
| Identifiers | |
| Latin | trigonum musculare |
| TA | A01.2.02.005 |
| FMA | 61601 |
| Anatomical terminology | |
The inferior carotid triangle (or muscular triangle), is bounded, in front, by the median line of the neck from the hyoid bone to the sternum; behind, by the anterior margin of the sternocleidomastoid; above, by the superior belly of the omohyoid.
The hyoid bone is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra (C3) behind.
Contents
It is covered by the integument, superficial fascia, platysma, and deep fascia, ramifying in which are some of the branches of the supraclavicular nerves.
Beneath these superficial structures are the sternohyoid and sternothyroid, which, together with the anterior margin of the sternocleidomastoid, conceal the lower part of the common carotid artery.
In anatomy, the left and right common carotid arteries (carotids) are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries.
This vessel is enclosed within its sheath, together with the internal jugular vein and vagus nerve; the vein lies lateral to the artery on the right side of the neck, but overlaps it below on the left side; the nerve lies between the artery and vein, on a plane posterior to both.
The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. The vein runs in the carotid sheath with the common carotid artery and vagus nerve.
The vagus nerve, historically cited as the pneumogastric nerve, is the tenth cranial nerve or CN X, and interfaces with the parasympathetic control of the heart, lungs, and digestive tract. The vagus nerves are paired but are normally referred to in the singular. It is the longest nerve of the autonomic nervous system in the human body.
In front of the sheath are a few descending filaments from the ansa cervicalis; behind the sheath are the inferior thyroid artery, the recurrent nerve, and the sympathetic trunk; and on its medial side, the esophagus, the trachea, the thyroid gland, and the lower part of the larynx.
The ansa cervicalis is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid triangle. Its name means "handle of the neck" in Latin.
The inferior thyroid artery is an artery in the neck. It arises from the thyrocervical trunk and passes upward, in front of the vertebral artery and longus colli muscle. It then turns medially behind the carotid sheath and its contents, and also behind the sympathetic trunk, the middle cervical ganglion resting upon the vessel.
The sympathetic trunks are a paired bundle of nerve fibers that run from the base of the skull to the coccyx.
By cutting into the upper part of this space, and slightly displacing the sternocleidomastoid, the common carotid artery may be tied below the omohyoid.
