The supreme intercostal artery descends anterior to rib I and divides to form the posterior intercostal arteries for the first two intercostal spaces.
Numerous veins pass through the root of the neck. Small veins accompany each of the arteries described above, and large veins form major drainage channels.
The subclavian veins begin at the lateral margin of rib I as continuations of the axillary veins. Passing medially on each side, just anterior to the anterior scalene muscles, each subclavian vein is joined by the internal jugular vein to form the brachiocephalic veins.
The only tributary to each subclavian vein is an external jugular vein.
The veins accompanying the numerous arteries in this region empty into other veins.
Several nerves and components of the nervous system pass through the root of the neck.
The phrenic nerves are branches of the cervical plexus and arise on each side as contributions from the anterior rami of cervical nerves C3 to C5 come together. Passing around the upper lateral border of each anterior scalene muscle, the phrenic nerves continue inferiorly across the anterior surface of each anterior scalene muscle within the prevertebral layer of cervical fascia (Fig. 8.192). Leaving the lower edge of the anterior scalene muscle each phrenic nerve passes between the subclavian vein and artery to enter the thorax and continue to the diaphragm.
The vagus nerves [X] descend through the neck within the carotid sheath, posterior to and just between the common carotid artery and the internal jugular vein.
In the lower part of the neck, the vagus nerves [X] give off cardiac branches, which continue downward and medially, passing posterior to the subclavian arteries to disappear into the thorax.
In the root of the neck, each vagus nerve [X] passes anterior to the subclavian artery and posterior to the subclavian vein as it enters the thorax (Fig. 8.192).
The right and left recurrent laryngeal nerves are visible as they originate in (the right recurrent laryngeal nerve), or pass through (the left recurrent laryngeal nerve), the root of the neck.
The right recurrent laryngeal nerve is a branch of the right vagus nerve [X] as it reaches the lower edge of the first part of the subclavian artery in the root of the neck. It passes around the subclavian artery and upward and medially in a groove between the trachea and the esophagus as it heads to the larynx.
The left recurrent laryngeal nerve is a branch of the left vagus nerve [X] as it crosses the arch of the aorta in the superior mediastinum. It passes below and behind the arch of the aorta and ascends beside the trachea to the larynx (Fig. 8.192).
Various components of the sympathetic nervous system are visible as they pass through the root of the neck (Fig. 8.193). These include: the cervical part of the sympathetic trunk, the ganglia associated with the cervical part of the sympathetic trunk, and cardiac nerves branching from the cervical part of the sympathetic trunk.
The sympathetic trunks are two parallel cords that run from the base of the skull to the coccyx. Along the way they are punctuated by ganglia, which are collections of neuronal cell bodies outside the CNS.
Cervical part of the sympathetic trunk
The cervical part of the sympathetic trunk is anterior to the longus colli and longus capitis muscles, and posterior to the common carotid artery in the carotid sheath and the internal carotid artery. It is connected to each cervical spinal nerve by a gray ramus communicans (Fig. 8.194). There are no white rami communicantes in the cervical region.