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Big Picture

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The neck region is divided into triangles to compartmentalize the contents. The sternocleidomastoid muscle divides the neck region into posterior and anterior triangles. The posterior triangle of the neck is located on the lateral aspect of the neck.

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Boundaries of the Posterior Triangle

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The boundaries of the posterior triangle are as follows (Figure 26-1A):

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  • Anteriorly. The sternocleidomastoid muscle.
  • Posteriorly. The trapezius muscle.
  • Inferiorly. The clavicle.

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Figure 26-1
Graphic Jump Location

A. Boundaries of the posterior triangle of the neck. B. Cross-section and lateral view of the deep investing fascia surrounding the sternocleidomastoid and trapezius muscles. C. Cross-section and lateral view of the prevertebral fascia covering the prevertebral muscles. D. Prevertebral fascia removed from the posterior triangle of the neck.

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Roof of the Posterior Triangle

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The roof of the posterior triangle of the neck consists of the investing layer of the deep cervical fascia that surrounds the neck, enveloping the sternocleidomastoid and trapezius muscles (Figure 26-1B). The sensory branches of the cervical plexus and the external jugular vein pierce the investing layer of cervical fascia.

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Sensory Branches of the Cervical Plexus

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The sensory branches of the cervical plexus course between the anterior and middle scalene muscles piercing the investing fascia at the posterior border of the sternocleidomastoid muscle en route to their respective cutaneous fields (Figure 26-1B).

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  • Lesser occipital nerve (C2 contribution). Ascends along the posterior border of the sternocleidomastoid muscle en route to the skin of the neck and scalp, behind the ear.
  • Great auricular nerve (C2–C3 contributions). Ascends over the sternocleidomastoid muscle en route to the skin of the parotid region and ear.
  • Transverse cervical nerve (C2–C3 contributions). Courses horizontally over the sternocleidomastoid muscle en route to the skin on the anterior and lateral sides of the neck.
  • Supraclavicular nerve (C3–C4 contributions). Descends obliquely across the posterior triangle of the neck to the skin over the clavicle and superior region of the thorax.

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External Jugular Vein

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The external jugular vein descends vertically across the superficial surface of the sternocleidomastoid muscle, between the platysma muscle and the investing fascia. The external jugular vein pierces the investing fascia where it joins with the subclavian vein.

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Floor of the Posterior Triangle

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The prevertebral fascia forms the floor of the posterior triangle of the neck (Figure 26-1C and D).

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The following structures are superficial to the prevertebral fascia:

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  • Inferior belly of the omohyoid muscle. Courses from the hyoid bone en route to the scapula within the pretracheal fascia.
  • Transverse cervical artery. A branch from the thyrocervical trunk that courses along the ...

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