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Triangles of the neck
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The triangles of the neck are the topographic areas of the neck bounded by the neck muscles. The sternocleidomastoid muscle divides the neck into the two major neck triangles; the anterior triangle and the posterior triangle of the neck, each of them containing a few subdivisions.
The triangles of the neck are important because of their contents, as they house all the neck structures, including glands, nerves, vessels and lymph nodes. For that reason, this article will discuss the anatomy, borders and contents of the triangles of the neck.
| Definition | Two triangular areas found anterior and posterior to the sternocleidomastoid muscles which contain the visceral structures of the neck. |
| Anterior triangle |
Borders: - Superior - inferior border of mandible - Medial - midline of neck - Lateral - anterior border of sternocleidomastoid muscle Subdivisions: - Muscular (omotracheal) triangle - Carotid triangle - Submandibular triangle - Submental triangle |
| Posterior triangle |
Borders: - Anterior - posterior margin of sternocleidomastoid muscle - Posterior - anterior margin of trapezius muscle - Inferior - middle one-third of clavicle Subdivisions: - Occipital triangle - Supraclavicular (omoclavicular) triangle |
Anatomical triangles
The median line of the neck divides the neck into symmetrical halves. The sternocleidomastoid muscle, in its oblique (posterosuperior) course, further divides the neck into anterior and posterior triangles. The anterior triangle of the neck is further subdivided into four smaller triangles, while the posterior triangle is broken up into two smaller triangles.
Master the triangles of the neck with our study unit which includes video tutorials, quizzes, labeled diagrams, and articles:
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Anterior triangle
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The anterior triangle is the triangular area of the neck found anteriorly to the sternocleidomastoid muscle. It is formed by the anterior border of sternocleidomastoid laterally, the median line of the neck medially and by the inferior border of the mandible superiorly. The apex of the anterior triangle extends towards the manubrium of sternum. The anterior triangle is further subdivided into the:
- Muscular (omotracheal/infrahyoid) triangle
- Carotid triangle
- Submandibular triangle
- Submental triangle
| Definition | Triangular area of the neck found anteriorly to the |
| Borders |
Superior - inferior border of mandible Medial - midline of neck Lateral - anterior boeder of sternocleidomastoid muscle |
| Subdivisions |
Muscular (omotracheal) triangle Carotid triangle Submandibular triangle Submental triangle |
| Contents |
Muscles: thyrohyoid, sternothyroid, sternohyoid muscles Organs: thyroid gland, parathyroid glands, larynx, trachea, esophagus, submandibular gland, caudal part of the parotid gland Arteries: superior and inferior thyroid, common carotid, external carotid, internal carotid artery (and sinus), facial, submental, lingual arteries Veins: anterior jugular veins, internal jugular, common facial, lingual, superior thyroid, middle thyroid veins, facial vein, submental vein, lingual veins Nerves: vagus nerve (CN X), hypoglossal nerve (CN XII), part of sympathetic trunk, mylohyoid nerve |
Muscular triangle
The muscular (omotracheal) triangle also shares one margin with the anterior triangle – the median line of the neck. However, the muscular triangle begins at the inferior border of the body of the hyoid bone. It has two posterior borders – the proximal part of the anterior border of sternocleidomastoid inferiorly and the anterior part of the superior belly of omohyoid superiorly.
| Borders |
Superior - hyoid bone Lateral - superior belly of omohyoid and anterior border of sternocleidomastoid Medial - midline of neck |
| Contents |
Muscles: thyrohyoid, sternothyroid, sternohyoid Vessels: superior and inferior thyroid arteries, anterior jugular veins Viscera: thyroid gland, parathyroid glands, larynx, trachea, esophagus |
The apex of the muscular triangle is at the intersection of sternocleidomastoid and omohyoid muscles. The muscular triangle contains: the infrahyoid muscles (thyrohyoid, sternothyroid, sternohyoid), vessels (superior and inferior thyroid arteries, anterior jugular veins) and viscera (thyroid and parathyroid glands, larynx, trachea, esophagus).
Carotid triangle
Similar to the muscular triangle, the carotid triangle has the omohyoid and sternocleidomastoid muscles as parts of its borders. However, it is the posterior margin of the superior omohyoid muscle that limits the triangle anteriorly and the anterior margin of the sternocleidomastoid posteriorly.
| Borders |
Anterior - superior belly of omohyoid muscle Superior - stylohyoid and posterior belly of digastric muscles Posterior - anterior border of sternocleidomastoid muscle |
| Contents |
Arteries: common carotid, external carotid (and branches except maxillary, superficial temporal and posterior auricular), internal carotid artery (and sinus) Veins: internal jugular, common facial, lingual, superior thyroid, middle thyroid veins Nerves: vagus nerve (CN X), hypoglossal nerve (CN XII), part of sympathetic trunk |
Superiorly, the posterior belly of the digastric muscle and stylohyoid close the triangle. It is floored by the inferior and middle pharyngeal constrictors, hyoglossus and parts of thyrohyoid. Its roof is formed by deep and superficial fascia, platysma and skin. This triangle contains major arteries, veins and nerves of the neck and head.
Submandibular (digastric) triangle
Like the anterior triangle, the digastric (submandibular) triangle is limited superiorly by the same structures. Its inferior boundaries are formed by the posterior belly of the digastric and stylohyoid muscles posteriorly, and the anterior belly of the digastric muscle anteriorly. The apex of the triangle rests at the intermediate tendon of the digastric muscle. Its floor is formed by the mylohyoid and hyoglossus, while it is roofed by skin, fascia and platysma.
| Borders |
Superior - inferior border of mandible Lateral - anterior belly of digastric muscle Medial - posterior belly of digastric muscle |
| Contents |
Viscera: submandibular gland and lymph nodes (anteriorly), caudal part of the parotid gland (posteriorly) Vessels: facial artery and vein, submental artery and vein, lingual arteries and veins Nerves: mylohyoid, hypoglossal (CN XII) |
The digastric triangle houses submandibular gland and lymph nodes (anteriorly), caudal part of the parotid gland (posteriorly), facial artery and vein, submental artery and vein, lingual arteries and veins, mylohyoid nerve and the hypoglossal nerve (CN XII).
Submental triangle
The submental triangle is located between the anterior bellies of the left and right digastric muscles. The base of the triangle is formed by the body of the hyoid bone and its apex extends towards the symphysis menti. This triangle, like the submandibular triangle, is floored by the mylohyoid muscles and roofed by the platysma, fascia and skin.
| Borders |
Inferior - hyoid bone Lateral - anterior belly of digastric muscle Medial - midline of neck |
| Contents | Anterior jugular vein, submental lymph nodes |
The submental triangle is occupied by the small venous tributaries to the anterior jugular vein, and the submental lymph nodes.
Posterior triangle
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The posterior triangle is a triangular area found posteriorly to the sternocleidomastoid muscle. It has three borders; anterior, posterior and inferior borders. The anterior border is the posterior margin of the sternocleidomastoid muscle. The posterior border is the anterior margin of the trapezius muscle, while the inferior border is the middle one-third of the clavicle.
Eek, this is a tricky topic - but keep going! Once you test yourself, you'll be surprised how much you know. Find out how you can identify gaps in your knowledge with our anatomy quiz questions.
The investing layer of deep cervical fascia and integument forms the roof of the space, while the floor is covered with the prevertebral fascia along with levator scapulae, splenius capitis and the scalene muscles. The inferior belly of omohyoid subdivides the posterior triangle into a small supraclavicular, and a large occipital, triangle.
| Borders |
Anterior - posterior margin of sternocleidomastoid muscle Posterior - anterior margin of trapezius muscle Inferior - middle one-third of clavicle |
| Subdivisions |
Occipital triangle Supraclavicular (omoclavicular) triangle |
| Contents |
Vessels: the third part of the subclavian artery, suprascapular and transverse cervical branches of the thyrocervical trunk, external jugular vein, lymph nodes Nerves: accessory nerve (CN XI), the trunks of the brachial plexus, fibers of the cervical plexus |
Occipital triangle
The anterior and posterior margins of the occipital triangle are the same as those of the posterior triangle. However, its base (inferior border) is now formed by the superior margin of the inferior belly of the omohyoid muscle.
| Borders |
Anterior - posterior margin of sternocleidomastoid muscle Posterior - anterior margin of trapezius muscle Inferior - inferior belly of omohyoid muscle |
| Contents | Accessory nerve (CN XI), branches of the cervical plexus, upper most part of brachial plexus, supraclavicular nerve |
The semispinalis capitis (occasionally), splenius capitis, levator scapulae and middle scalene and posterior muscles line the floor of the occipital triangle in that craniocaudal order. The roof of the triangle is (from superficial to deep) skin, superficial and deep fascia.
Supraclavicular (omoclavicular) triangle
Finally, the supraclavicular triangle (greater supraclavicular fossa) is the smaller of the two posterior triangles. It shares anterior and inferior margins with the posterior triangle. However, it is limited superiorly by the inferior border of omohyoid. Scalenus medius, the first digitation of serratus anterior and the first rib are in the floor of this triangle. The roof is formed from the skin, fascia and platysma.
| Borders |
Superior - inferior belly of omohyoid muscle Anterior - posterior edge of sternocleidomastoid muscle Inferior - clavicle |
| Contents | Third part of the subclavian artery, brachial plexus trunks, nerve to subclavius muscle, lymph nodes |
The subdivisions of the posterior triangle are occupied by the regional lymph nodes, the third part of the subclavian artery, suprascapular and transverse cervical branches of the thyrocervical trunk, external jugular vein, trunks of the brachial plexus and the fibers of the cervical plexus.
In addition, we strongly recommend that you crown your knowledge by reviewing our clinical cases. Every neck triangle contains a group of lymph nodes, but what happens when they become enlarged and compress adjacent structures? You can find that out in our case of Horner's Syndrome. Also, the thyroid gland contained in the anterior triangle of the neck can be affected with an inflammatory process within Hashimoto's disease. Learn about it with our article.
Solidify your knowledge about the triangles of the neck with our quiz:
Clinical significance
Knowledge of the triangles of the neck and their contents are extremely important for clinical examinations and surgical procedures. These clinical and surgical procedures include, but are not limited to:
- Evaluation of the jugular venous pressure
- Evaluation of the pulses in a cardiovascular exam
- Emergency airway management
Jugular venous pressure
Jugular venous pressure (JVP) is an indirect measurement of the pressure within the venous system. This is possible because the internal jugular vein has valveless communication with right atrium, therefore blood can flow backward into the vessel. With the patient lying at a 30 - 45 degree angle and their head turned to the left, an elevated JVP will appear as a collapsing pulsation between the distal parts of the sternocleidomastoid in the supraclavicular triangle and can extend as far as the lobule of the ear. The JVP is measured as the vertical distance from the sternal angle of Louis to the top of the pulsation. An elevated JVP (greater than 3 cm) is indicative of several pathologies, including but not limited to pulmonary hypertension, hepatic congestion and right heart failure.
Carotid artery pulsation
Identification of the carotid artery pulsation is important in the examination of the cardiovascular system. It is often compared with the pulsation of the radial artery. The pulsation of the carotid artery can be appreciated by palpating the region of the carotid triangle. Radio-carotid delay usually suggest atypical coarctation of the aorta.
Cricothyroidotomy
A cricothyroidotomy is an emergency procedure used to establish a patent airway when other less invasive procedures (endotracheal intubation, laryngeal mask airway, etc) are contraindicated or would provide suboptimal care. It is a sterile procedure that involves incision of the cricothyroid membrane (caudal to the inferior border of the thyroid cartilage and cranial to the superior border of the cricoid cartilage). The membrane is an avascular plane deep to the region of the muscular triangle that allows for quick access to the airway until a formal tracheostomy can be performed.
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