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There are various techniques for categorizing the complex anatomy of the neck. Based on anatomic boundaries, the neck is divided into anterior and posterior triangles and suprahyoid and infrahyoid regions. The boundaries of the posterior triangle are the sternocleidomastoid muscle (SCM) anteriorly, the trapezius muscle posteriorly, and the middle third of the clavicle inferiorly. The apex of the posterior triangle is the point at which the sternocleidomastoid and trapezius muscles meet at the occipital bone. The roof of the posterior triangle is formed by the investing layer of the cervical fascia, and the floor consists of the muscles covered by the prevertebral layer of the cervical fascia. The posterior triangle is further divided into supraclavicular and occipital triangles by the inferior belly of the omohyoid muscle. The occipital triangle contains posterior branches of the cervical plexus, the accessory nerve, trunks of the brachial plexus, a portion of the external jugular vein, and cervical lymph nodes. The supraclavicular triangle contains a portion of the subclavian artery, the suprascapular artery, and supraclavicular lymph nodes.

The boundaries of the anterior triangle of the neck are the median line anteriorly, the SCM posteriorly, and the inferior margin of the mandible superiorly. The apex of the triangle is at the suprasternal notch of the manubrium. The roof of the anterior triangle is formed by subcutaneous tissue containing the platysma muscle and the floor is formed by the pharynx, larynx, and thyroid gland. The anterior triangle is further divided into submandibular, submental, carotid, and muscular triangles by the digastric and omohyoid muscles. The submandibular triangle contains the submandibular gland (SMG), submandibular lymph nodes, the hypoglossal nerve, and parts of the facial artery and vein. The submental triangle contains submental lymph nodes. The carotid triangle contains the carotid artery, internal jugular vein, vagus nerve, external carotid artery, hypoglossal nerve, sympathetic trunk, accessory nerve, thyroid gland, larynx, pharynx, cervical lymph nodes, and branches of the cervical plexus. The muscular triangle contains the sternothyroid and sternohyoid muscles, the thyroid gland, and the parathyroid glands.

The boundaries of the nasopharynx consist of the choanae anteriorly, the sphenoid sinus superiorly, the clivus posteriorly, and the soft palate inferiorly. The parapharyngeal space is peripheral to the nasopharynx and is separated from it by the pharyngobasilar fascia, which is the superior extension of the superior constrictor muscle. The infratemporal fossa (masticator space) is lateral to the parapharyngeal space and inferior to the middle cranial fossa. The retropharyngeal space is a potential space between the visceral fascia posterior to the larynx and the prevertebral fascia; it extends from the skull base to the mediastinum. Multiple lymph nodes are located in the retropharyngeal space; these nodes serve lymphatics in the nasopharynx, paranasal sinuses, and temporal bones. The retropharyngeal space is a common site of neck infection (Table 30-1).

Table 30–1.Selected Anatomic Spaces of the Neck and Common Pathology...

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