The investing layer of the deep cervical fascia, the most superficial deep fascial layer, surrounds the entire neck deep to the skin and subcutaneous tissue (Fig. 8.2). At the "four corners" of the neck, the investing layer splits into superficial and deep layers of fascia to enclose (invest) the sternocleidomastoid (SCM) and trapezius muscles.
Inferiorly, the investing layer of fascia attaches to the manubrium of the sternum, clavicles, acromions, and spines of the scapulae. The investing layer is continuous posteriorly with the periosteum covering the C7 spinous process and the nuchal ligament (L. ligamentum nuchae) (Fig. 8.2B). Just superior to the manubrium, the fascia remains divided into the two layers that enclose the SCM; one layer attaches to the anterior and the other to the posterior surface of the manubrium.
The investing layer of deep cervical fascia helps prevent the spread of abscesses. If an infection occurs between the investing layer of deep cervical fascia and the muscular part of the pretracheal fascia surrounding the infrahyoid muscles, the infection usually does not spread beyond the superior edge of the manubrium. If, however, the infection occurs between the investing fascia and the visceral part of the pretracheal fascia, it can spread into the thoracic cavity anterior to the pericardium.
The arteries in the lateral cervical region are:
1.Cervicodorsal trunk (transverse cervical artery) 2.Suprascapular artery
3.Third part of the subclavian artery, and
4. Part of the occipital artery
The cervicodorsal trunk originates from the thyrocervical trunk, a branch of the subclavian artery, and divides into the superficial cervical and dorsal scapular arteries. The cervicodorsal trunk runs superficially and laterally across the phrenic nerve and anterior scalene muscle, 2 to 3 cm superior to the clavicle. It then crosses (passes through) the trunks of the brachial plexus, supplying branches to their vasa nervorum (blood vessels of nerves) and passing deep to the trapezius.
The superficial cervical artery accompanies CN XI along the anterior (deep) surface of the trapezius. The dorsal scapular artery runs anterior to the rhomboid muscles, accompanying the dorsal scapular nerve. The dorsal scapular artery may arise independently, directly from the subclavian artery.
The suprascapular artery, from the cervicodorsal trunk, a branch of the thyrocervical trunk, or from the subclavian artery, passes inferolaterally across the anterior scalene muscle and phrenic nerve. It crosses the subclavian artery (third part) and the cords of the brachial plexus. It then passes posterior to the clavicle to supply muscles on the posterior aspect of the scapula. The suprascapular artery may arise directly from the subclavian artery.
The occipital artery, a branch of the external carotid artery (Fig. 8.5A), crosses the lateral cervical region at its apex and ascends to supply the posterior half of the scalp.
The third part of the subclavian artery supplies blood to the upper limb. It begins approximately a finger's breadth superior to the clavicle, opposite the lateral border of the anterior scalene muscle. It lies posterosuperior to the subclavian vein in the inferior part of the lateral cervical region (Fig. 8.4E). The pulsations of the artery can be felt
on deep pressure in the omoclavicular triangle just superior to the clavicle (Fig. 8.3). The artery is in contact with the first rib as it passes posterior to the anterior scalene muscle; consequently, compression of the artery against this rib can control bleeding in the upper limb.
The veins in the posterior triangle of the neck are:
3.Anterior Jugular Vein
4.Internal Jugular Vein
5.External Jugular Vein
The external jugular vein begins near the angle of the mandible (just inferior to the auricle of the external ear) by the union of the posterior division of the retromandibular vein with the posterior auricular vein (Fig. 8.4A). The EJV crosses the SCM obliquely, deep to the platysma, and then pierces the investing layer of deep cervical fascia, which forms the roof of this region, at the posterior border of the SCM. The EJV descends to the inferior part of the lateral cervical region and terminates in the subclavian vein.
The major venous channel draining the upper limb, the subclavian vein, courses through the inferior part of the lateral cervical region, passing anterior to the anterior scalene muscle and phrenic nerve (Fig. 8.4E). The subclavian vein joins the IJV to form the brachiocephalic vein posterior to the medial end of the clavicle (Fig. 8.4A, E). Just superior to the clavicle, the EJV receives the cervicodorsal (transverse cervical), suprascapular, and anterior jugular veins.