Table of Contents · 6 sections
The triangles of the neck are topographic regions whose knowledge is essential for surgeons, anesthesiologists, and anatomists. Each triangle has defined boundaries and contains specific vessels, nerves, and organs. This article provides a complete systematization with tables, clinical significance, and mnemonics.
Two main triangles of the neck
The sternocleidomastoid muscle (SCM) divides the neck into two large triangles:
| Triangle | Boundaries | Location |
|---|---|---|
| Anterior (medial) | Anteriorly — midline of the neck, posteriorly — SCM, superiorly — inferior border of the mandible | Contains neck organs (larynx, trachea, thyroid gland, vessels) |
| Posterior (lateral) | Anteriorly — SCM, posteriorly — trapezius muscle, inferiorly — clavicle | Contains scalene muscles, subclavian vessels, brachial plexus |
Subdivisions of the anterior triangle
| Triangle | Boundaries | Contents | Clinical significance |
|---|---|---|---|
| Submandibular | Inferiorly — anterior and posterior bellies of the digastric muscle, superiorly — mandible | Submandibular salivary gland, facial artery and vein, lymph nodes, hypoglossal nerve (XII) | Submandibular gland excision, lymphadenectomy. Preserve the XII nerve and the marginal mandibular branch of the VII! |
| Submental | Laterally — anterior bellies of the digastric muscles, inferiorly — hyoid bone | Lymph nodes, small veins | Drainage of floor-of-mouth abscesses, metastasis from lower lip/chin cancer |
| Carotid | Superiorly — posterior belly of the digastric, anteriorly — superior belly of the omohyoid, posteriorly — SCM | Common and internal carotid arteries, internal jugular vein, vagus nerve (X), superior laryngeal nerve | Carotid endarterectomy, approach to the thyroid gland. Carotid bifurcation is at the level of the upper border of the thyroid cartilage |
| Muscular (omotracheal) | Superiorly — omohyoid, laterally — SCM, medially — midline | Thyroid and parathyroid glands, trachea, recurrent laryngeal nerve, inferior thyroid artery | Thyroidectomy, tracheostomy. Injury to the recurrent nerve → hoarseness |
Subdivisions of the posterior triangle
| Triangle | Boundaries | Contents | Clinical significance |
|---|---|---|---|
| Omoclavicular (subclavian) | Superiorly — inferior belly of the omohyoid, anteriorly — SCM, inferiorly — clavicle | Subclavian artery (3rd part), subclavian vein, brachial plexus, external jugular vein | Subclavian vein catheterization, brachial plexus block, injuries to subclavian vessels |
| Omotrapezoid | Anteriorly — SCM, posteriorly — trapezius, inferiorly — omohyoid | Accessory nerve (XI), cervical plexus (cutaneous branches), posterior chain lymph nodes | Lymph node biopsy: beware of the XI nerve! Injury → inability to raise the arm above the horizontal plane |
Fasciae of the neck
The neck has 3 fascial layers (according to Terminologia Anatomica):
- Superficial fascia (subcutaneous) — envelops the platysma
- Investing fascia (superficial layer) — forms sheaths for the SCM and trapezius, and capsules for the submandibular and parotid glands
- Deep fascia:
- Pretracheal layer — envelops the infrahyoid muscles and the thyroid gland
- Prevertebral layer — covers the prevertebral and scalene muscles
- Carotid sheath — surrounds the carotid artery, internal jugular vein, and vagus nerve
Clinically important landmarks
- Bifurcation of the common carotid artery — upper border of the thyroid cartilage (C3-C4 level)
- Cricoid cartilage — C6 level (landmark for cricothyroidotomy, origin of the trachea)
- Erb's point — midpoint of the posterior border of the SCM: emergence site of 4 cutaneous nerves of the cervical plexus (lesser occipital, great auricular, transverse cervical, supraclavicular)
- Accessory nerve (XI) — crosses the posterior triangle superficially → easily injured during lymph node biopsies
Frequently asked questions
Why is it important to identify the recurrent laryngeal nerve during a thyroidectomy?
The recurrent laryngeal nerve (branch of X) innervates all laryngeal muscles except the cricothyroid. It runs in the tracheoesophageal groove near the inferior thyroid artery, which is the surgical zone during thyroidectomy. Unilateral injury → hoarseness (vocal cord paresis). Bilateral injury → stridor, asphyxia (emergency intubation/tracheostomy).
Where are tracheostomy and cricothyroidotomy performed?
Tracheostomy: between the 2nd and 3rd (or 3rd and 4th) tracheal rings, below the thyroid gland isthmus. Cricothyroidotomy (emergency): through the cricothyroid membrane (between the thyroid and cricoid cartilages), at the C5-C6 level. Cricothyroidotomy is faster and safer in an emergency.
Study topographic anatomy through interactive lessons on the platform. Related topics: cranial nerves, muscles of the upper extremity, acute abdomen. Use clinical calculators for anatomical calculations.