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Chapter 4: Head and Neck

POSTERIOR TRIANGLE OF THE NECK

The posterior triangle of the neck contains many important landmarks and nervous structures, some of which were already identified in past dissections but which we will now locate as they travel within the neck. But first, there are superficial structures that will need to be identified. The platysma is a thin sheet of skeletal muscle that is invested with the superficial fascia across the anterior and lateral neck. Be cautious when using a scalpel not to miss this muscle of facial expression. Posterior to the sternocleidomastoid, emerging collectively at a landmark called Erb's Point, are a collection of sensory nerves for the neck that are part of the cervical plexus. After locating these structures move deeper to find the scalenes and the trunks of the brachial plexus.

  1. image Turn the cadaver to the supine position.

  2. Carefully remove only the epidermis and dermis but not the superficial fascia beginning at the mastoid process posterior to the ear diagonally to the sternum and laterally along the clavicle bilaterally.

  3. Identify and reflect superiorly the platysma, a thin muscle in superficial fascia of the neck that extends from the mandible to the clavicle. Clean the posterior triangle within sternocleidomastoid, trapezius, and the clavicle.

  4. Identify the spinal accessory nerve posterior to the sternocleidomastoid heading to the trapezius.

  5. Note lesser occipital, great auricular, transverse cervical, and supraclavicular nerves of the cervical plexus emerging posterior to the midpoint of sternocleidomastoid at the location called Erb's Point (Figure 4.1).

Figure 4.1

Posterior triangle of the neck including Erb's point.

A photo shows the posterior triangle of neck along with Erb’s point. The photo shows the posterior triangle of neck along with Erb’s point. Above the Erb’s point lies the lesser occipital nerve, great auricular nerve, transverse cervical nerve, sternocleidomastoid and muscle. To the right of Erb’s point lies the levator scapula. Below Erb’s point to the left lies the supraclavicular nerves, anterior scalene muscle, and external jugular vein. Below Erb’s point to the right lies the spinal accessory nerve, trapezius muscle, suprascapular artery, suprascapular nerve, suprascapular vein, omohyoid inferior belly, and prevertebral facia.
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  1. Identify the inferior belly of the omohyoid muscle. Identify the anterior scalene and middle scalene muscles on the floor of the triangle. Located between the anterior and middle scalene muscles, identify a large nerve plexus, the brachial plexus. Identify the dorsal scapular nerve, which arises from C5 ventral ramus, and suprascapular nerve, which branches from the superior trunk.

ANTERIOR TRIANGLES OF THE NECK

The anterior triangles of the neck contain the critical neurovasculature that transits the neck between the cranium and the thoracic cavity. Here you will identify the jugular veins, carotid artery, and branches of the cervical nerves that innervate the infrahyoid, or “strap,” muscles. The ansa cervicalis is a loop of cervical motor nerves and you will find this structure embedded within the carotid fascia that covers the carotid artery, internal jugular vein, and vagus nerve. Be careful to identify this nerve and its branches before opening the carotid sheath. Landmarks for this dissection are the hyoid bone and the hypoglossal nerve lateral and slightly superior to the hyoid bone. Part of the cervical spinal nerves that form the ansa cervicalis briefly join hypoglossal nerve before branching to form the superior root of the ansa cervicalis. Tracing the hypoglossal ...

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