The Root Of The Neck

The Root of the Neck

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Triangles of the neck | Main Anatomy Index | Neck Index | The larynx

Last updated 1 April 2006

The Root of the Neck

The root of the neck or thoracocervical region is the junction between the thorax and neck.
It includes the superior thoracic aperture through which pass all the structures going from the head to the thorax and vice versa.

Boundaries of the Root of the Neck (p. 807)

Laterally: the first pair of ribs and their costal cartilages.
Anteriorly: manubrium of the sternum.
Posteriorly: body of T1.

Arteries in the Root of the Neck (p. 807)

The arteries in this junctional area originate from the arch of the aorta.
They are the brachiocephalic trunk on the right side and the common carotid and subclavian arteries on the left side.

The Brachiocephalic Trunk (pp. 807, 809)

This trunk (artery) is the largest branch of the arch of the aorta.
It is 4 to 5 cm in length and arises posterior to the centre of the manubrium.
It passes superiorly and to the right, posterior to the right sternoclavicular joint, where it divides into the right common carotid artery and the right subclavian artery.

The brachiocephalic trunk is covered anterior by the sternohyoid and sternothyroid muscles.
At first, it lies on the trachea, and then to its right side.

Usually, the brachiocephalic trunk has no branches, other than its terminal branches (right subclavian and common carotid arteries).
Sometimes, however (10% of people), a small vessel called the thyroid ima artery (L. ima, lowest) arises from it and ascends anterior to the trachea to supply the isthmus of the thyroid gland.
This may be a potential source of serious bleeding in surgical operations of the thyroid gland.

The Subclavian Arteries (p. 809)

Click here for a diagram of the subclavian and carotid arteries.

These are the arteries of the upper limb but they also supply branches to the neck and brain.
The right subclavian artery is a terminal branch of the brachiocephalic trunk and arises posterior to the right sternoclavicular joint.
The left subclavian artery arises from the arch of the aorta and enters the root of the neck by passing superiorly, posterior to the left sternoclavicular joint.

Each subclavian artery arches superiorly, posteriorly and laterally, grooving the pleura of the lung and then inferiorly, posterior to the midpoint of the clavicle.
As theses arteries rise 2-4 cm into the root of the neck, they are crossed by the scalenus anterior muscles.

For the purposes of description, the scalenus anterior muscle divides the subclavian artery into 3 parts.
1^st part: medial to the scalenus anterior muscle.
2^nd part: posterior to the muscle.
3^rd part: lateral to the muscle.

The branches of the subclavian artery are: (1) the vertebral artery; (2) the internal thoracic artery; (3) the thyrocervical trunk; (4) the costocervical trunk; and (5) the dorsal scapular.
On the left, all branches except the dorsal scapular arises from the first part.
On the right, the costocervical trunk usually arises from its 2^nd part.

The Vertebral Arteries (p. 809)

Click here to go to the vertebral artery in the blood supply of the brain.

The Internal Thoracic Artery (p. 809)

The internal thoracic arteries (click here to go the intercostal region) arise from the inferior aspect of the subclavian artery and passes inferomedially into the thorax.
It runs parallel to the sternum and gives off anterior intercostal branches to the first six intercostal spaces.

The Thyrocervcial Trunk (p. 809)

This arises from the first part of the subclavian artery, just medial to the scalenus anterior muscle.

It gives of several branches.
The largest and most important branch is the inferior thyroid artery, which passes to the inferior pole of the thyroid gland.
Another branch is the suprascapular artery (except when it arises from the third part of the subclavian artery) which supplies the muscles around the scapula.
The transverse cervical artery is also a branch, sending arterial branches to the muscles in the posterior triangle of the neck.

The Costocervical Trunk (p. 809)

This arises from the posterior aspect of the subclavian artery and passes superoposteriorly over the cervical pleura.
It divides into the superior intercostal and deep cervical arteries.
These supply the first two intercostal (posterior) spaces and the muscles of the neck.

The Dorsal Scapular Artery (Grant's Method of Anatomy, 8^th ed. p. 502)

Usually (67%; Huelke) springs from the 2^nd or 3^rd part of the subclavian artery.
It follows the nerve to the rhomboids, or dorsal scapular nerve deep to the levator scapulae.

Veins of the Root of the Neck (pp. 809, 811)

The Anterior Jugular Vein (p. 811)

This is usually the smallest of the jugular veins.
It arises near the hyoid bone from the confluence of the submandibular veins, which is sometimes called the submental venous plexus.
It descends in the superficial fascia between the anterior median line and the anterior border of the SCM.

At the root of the neck, the anterior jugular vein turns laterally, posterior to the SCM, and opens into the termination of the external jugular vein or directly into the subclavian vein.
There are usually 2 anterior jugular veins.
Just superior to the sternum, the right and left anterior jugular veins are united by a large transverse trunk, the jugular venous arch.

The Subclavian Vein (p. 811)

This large vein is the continuation of the axillary vein.
It begins at the lateral border of the 1^st rib and ends at the medial border of the scalenus anterior muscle.
Here it is united with the internal jugular vein, posterior to the medial end of the clavicle to form the brachiocephalic vein.

The subclavian vein, which lies on the concavity of the subclavian artery superior to the clavicle, has a bicuspid valve near its termination.
It usually has only one tributary, the external jugular vein.

The subclavian vein passes over the first rib parallel to the subclavian artery but is separated from it by the scalene tubercle.
This tubercle separates the groove in the first rib for the subclavian vein and the groove for the subclavian artery.

The Internal Jugular Vein (p. 811)

Click here to go to the entry in the blood supply of the head.

This vein ends posterior to the medial end of the clavicle by uniting with the subclavian to form the brachiocephalic vein.
Throughout its course, the internal jugular vein is enclosed in the carotid sheath.

Nerves in the Root of the Neck

The Vagus Nerve (pp. 811, 813)

Click here to go to its entry under cranial nerves.
The vagus nerve is the main parasympathetic nerve to the organs of the thorax and abdomen.

It passes inferiorly in the posterior part of the carotid sheath in the angle between and posterior to the internal jugular vein and carotid artery.
On the right side, CN X crosses the origin of the subclavian artery, posterior to the brachiocephalic vein and the sternoclavicular joint to enter the thorax.

The recurrent laryngeal nerve, a branch of CN X loops around the subclavian artery on the right side and around the arch of the aorta on the left.
These nerves pass superiorly to reach the posteromedial aspect of the inferior pole of the thyroid gland, where they ascend in the tracheoesophageal groove.
They supply all the intrinsic muscles of the larynx except the cricothyroid.

The Phrenic Nerve (p. 813)

This is the sole motor nerve of the thoracic diaphragm.
Click here to go to the phrenic nerve (cervical plexus).

The Sympathetic Trunks

Click here to go to the section in the ANS.
These trunks receive no white rami communicates in the neck, but they contain three cervical sympathetic ganglia (superior, middle and inferior).
These ganglia receive their preganglionic fibres from the superior thoracic spinal nerves though white rami communicantes.
From these sympathetic trunks, fibres pass to cervical structures as postganglionic fibres in the cervical spinal nerves or leave as direct visceral branches.
Branches to the head run with the arteries, especially the internal and external carotid arteries.

The Inferior Cervical Ganglion (pp. 814-5)

It lies at the level or the superior border of the neck of the first rib, where it is wrapped around the posterior aspect of the vertebra artery.
It is usually fused with the first thoracic ganglion to form a large ganglion, known as the cervicothoracic (stellate) ganglion.

This ganglion lies anterior to the TP of the vertebra prominens (C7), just superior to the neck of the 1^st rib on each side and posterior to the origin of the vertebral artery.

The Middle Cervical Ganglion (p. 815)

This lies on the anterior aspect of the inferior thyroid artery, around the level of the cricoid cartilage and the transverse process of C6, just anterior to the vertebral artery.

The Superior Cervical Ganglion (p. 815)

This is located at the level of the atlas (C1) and axis (C2).
Because of its size, it forms a good landmark for locating the sympathetic trunk in the neck.
Postganglionic branches from it pass along the internal carotid artery and enter the cranial cavity.

Horner's Syndrome

Severance of a sympathetic trunk in the neck interrupts the sympathetic nerve supply to the head and neck on that side.
Horner's syndrome consists of:

pupillary constriction-paralysis of the dilator pupillae muscle in the iris.
ptosis, (lowering of the upper eyelid)-paralysis of smooth muscle in the levator palpebrae superioris.
sinking of the eye-paralysis of the orbitalis muscle.
vasodilation and absence of sweating on the face and neck-lack of sympathetic nerve supply to the blood vessels and sweat glands.

Lymphatics in the Root of the Neck (p. 815)

Several large lymph nodes are located in the carotid sheath along the blood vessels of the neck, particularly the internal jugular vein.
Another group of nodes is found along the transverse cervical artery.
All these are called the deep cervical lymph nodes because they are deep to the deep cervical fascia.

From the inferior end of the deep group of cervical lymph nodes, a jugular lymph trunk emerges and joins the venous system near the junction of the internal jugular and the subclavian veins.
On the left side, the jugular lymph trunk may drain into the thoracic duct.

The Thoracic Duct (pp. 815-6)

This is a lymphatic channel passes superiorly from the thorax through the superior thoracic aperture at the left border of the oesophagus.
It then arches laterally in the root of the neck, posterior to the carotid sheath, and anterior to the sympathetic trunk and vertebral and subclavian arteries.

The thoracic duct enters the left brachiocephalic vein at the junction of the subclavian and internal jugular veins.

It drains lymph from the entire body, except the right side of the head and neck, the right upper limb and the right side of the thorax.