Triangles of the Neck

Original Editor - Carina Therese Magtibay

Top Contributors - Carina Therese Magtibay, Ewa Jaraczewska and Kim Jackson

Description

The neck is the anatomical region that supports the head and serves as a conduit for vital structures passing to and from the torso. As a geometric region, it can be clinically divided using anatomical triangles.

The sternocleidomastoid muscle obliquely crosses the neck to form the division between the two major neck triangles: anterior triangle and posterior triangle. Both triangles are further divided into sub-triangles.

1. Anterior Triangle
   • Digastric/Submandibular Triangle
   • Carotid Triangle
   • Muscular Triangle
   • Submental Triangle
2. Posterior Triangle
   • Occipital Triangle
   • Subclavian/Supraclavicular

The neck is limited:

• superiorly by the inferior border of the mandible
• anteriorly by the midline of the neck
• inferiorly by the superior border of the clavicle
• posteriorly by the anterior margin of the trapezius muscle.

Anterior Triangle

Borders:

• Superior border - inferior border of the mandible
• Medial border- midline of the neck
• Lateral border- anterior border of the sternocleidomastoid muscle

The Anterior Triangle has an apex extending to the sternum's manubrium. It is made up of three paired triangles: submandibular (digastric), carotid, and muscular (omotracheal/infrahyoid) triangles, and one unpaired triangle: submental triangle.

Submandibular/Digastric Triangle

Borders:

• Superior - inferior border of the mandible
• Anterior - anterior belly of digastric muscle
• Posterior - the posterior belly of the digastric muscle
• Inferior - hyoid bone

Floor: mylohyoid muscle

Contents:

• Glands and lymphatics: submandibular gland and lymph nodes, lower pole of the parotid gland.
• Blood vessels: facial, lingual and submental arteries and veins
• Nerves: marginal mandibular branch of the facial nerve, nerve to the mylohyoid, hypoglossal nerve (CN XII)

Clinical Significance:

• Neoplasms, infectious and immunologic pathologies can arise from the submandibular triangle.
• Sialadenitis- inflammation of the submandibular salivary gland. The most common pathology seen in the submandibular triangle.
• Pleomorphic adenoma- the most common benign neoplasm arising in the submandibular triangle followed by adenolymphoma, also known as Warthin’s tumour
• Adenoid cystic carcinoma- the most common malignant neoplasm in the submandibular triangle, followed by mucoepidermoid carcinoma.

Carotid Triangle

Borders:

• Superior - stylohyoid and posterior belly of digastric muscles
• Anterior - the superior belly of the omohyoid muscle
• Posterior - anterior border of the sternocleidomastoid muscle

Floor: hyoglossus, thyrohyoid, and inferior and middle pharyngeal constrictor muscles

Contents:

• Arteries: common carotid and its bifurcation into internal and external carotid arteries, superior thyroid, lingual, facial, occipital, and ascending pharyngeal arteries
• Veins: internal jugular, superior thyroid, lingual, facial, ascending pharyngeal, and occipital veins
• Nerves: external and internal branches of the superior laryngeal nerve arising from the vagus nerve (CN X), hypoglossal nerve (CN XII).

Clinical Significance:

• Distention of the jugular vein can be palpated and assessed in the carotid triangle
• Internal jugular vein is usually utilized to establish central venous access for parental nutrition, dialysis, and administration of chemotherapy drugs.
• Carotid sinus is a baroreceptor that regulates blood pressure. Carotid sinus massage can be performed to terminate supraventricular tachycardia and other cardiac arrhythmias as.

Muscular Triangle

Borders:

• Anterior- midline of the neck
• Inferoposterior- anterior margin of the sternocleidomastoid muscle
• Posterosuperior- the superior belly of the omohyoid muscle

Contents:

• Blood vessels: superior thyroid artery, anterior jugular and inferior thyroid veins
• Lymphatics: anterior cervical, infrahyoid, prelaryngeal, thyroid, pretracheal, paratracheal lymph nodes
• Muscles: thyrohyoid, sternothyroid, sternohyoid, omohyoid muscles
• Nerves: ansa cervicalis (C1-3)
• Organs: esophagus, trachea, thyroid gland, and the lower part of the larynx

Clinical Significance:

• Tracheostomy and thyroidectomy- surgically accessed through the muscular triangle
• Injury of the superior thyroid artery can result in bleeding during surgery.

Submental Triangle

Borders:

• Inferior - hyoid bone
• Lateral - the anterior belly of the digastric muscle
• Medial - midline of the neck

Floor: mylohyoid muscle

Contents:

• submental lymph nodes
• anterior jugular vein

Clinical Significance:

• Tumors and cysts develop within the submental triangle
• Abscess from odontogenic infections can spread into the submental space
• Swollen submental lymph nodes can be indicative of malignant lesions. However, lesions in this area commonly develop from a local and benign pathology of the head and neck
• The submental lymph nodes are commonly involved in the metastasis of oral cavity cancer

Posterior Triangle

Borders:

• Anterior - posterior margin of sternocleidomastoid muscle
• Posterior - anterior margin of trapezius muscle
• Inferior - middle one-third of clavicle

Two subdivisions are formed within the posterior triangle: Occipital Triangle and the Subclavian/Supraclavicular Triangle

Occipital Triangle

Borders:

• Anterior - posterior margin of sternocleidomastoid muscle
• Posterior - anterior margin of trapezius muscle
• Inferior - the inferior belly of the omohyoid muscle

Floor: levator scapulae, splenius capitis, and middle and posterior scalene muscles

Contents:

• Artery: transverse cervical artery
• Lymphatics: accessory lymph nodes and inferior deep lateral cervical lymph nodes
• Nerves: accessory nerve (CN XI), cutaneous and muscular branches of the cervical plexus, the uppermost part of brachial plexus, supraclavicular nerves

Clinical Significance:

• A lot of nerves pass through the occipital triangle. It houses major nerves that innervate muscles vital for head and neck functions

Subclavian/Supraclavicular/Omoclavicular Triangle

Borders:

• Superior - the inferior belly of the omohyoid muscle
• Anterior-posterior edge of the sternocleidomastoid muscle
• Inferior - clavicle

Contents:

• Blood vessels: subclavian artery and vein
• Nerves: brachial plexus trunks and nerve to subclavius muscle
• Lymphatics: supraclavicular lymph nodes

Clinical Significance:

• Virchow’s node, the left-sided supraclavicular lymph node, can be used to aid in the discovery and diagnosis of carcinomas originating from the abdomen. Troisier’s sign (an enlarged, firm, non-tender Virchow’s node) can indicate cancer arising from the stomach, ovaries, testicles, and kidneys.
• The right-sided supraclavicular lymph node drains lymphatic fluid from the thorax. A firm, enlarged, non-tender right-sided supraclavicular lymph node can indicate metastasis from lung or oesophagal cancer and Hodgkin’s lymphoma.