Download Cervical Plexus

The Root of the neck
The Root of the neck
The Root of the Neck can be defined as area of the neck immediately
above the inlet into the thorax.
Muscles of the Root of the Neck
Scalenus Anterior Muscle
The scalenus anterior muscle is a key muscle in understanding the
root of the neck .It is deeply placed and it descends almost vertically
from the vertebral column to the 1st rib.
• Important Relations
• Anteriorly: Related to the carotid arteries, the vagus nerve, the internal jugular
vein and the deep cervical lymph nodes. The transverse cervical and
suprascapular arteries and the prevertebral of deep cervical fascia bind the
phrenic nerve to the muscle.
• Posteriorly :Related to the pleura, the origin of the brachial plexus, and the
second part of the subclavian artery. The scalenus medius muscle lies behind the
scalenus anterior muscle.
• Medially :Related to the vertebral artery and vein and the sympathetic trunk. On
the left side, the medial border is related to the thoracic duct.
• Laterally: Related to the emerging branches of the cervical plexus, the roots of
the brachial plexus, and the third part of the subclavian artery .
Scalenus Medius
The scalenus medius lies behind the scalenus anterior and extends
from the transverse process of the atlas and the transverse processes
of the next five cervical vertebrae downward and laterally to be
inserted into the upper surface of the 1st rib behind the groove for the
subclavian artery. The muscle lies behind the roots of the brachial
plexus and the subclavian artery.
The Thoracic Duct
• The thoracic duct begins in the abdomen at the upper end of the
cisterna chyli. It enters the thorax through the aortic opening in the
diaphragm and ascends through the posterior mediastinum, inclining
gradually to the left. On reaching the superior mediastinum, it is found
passing upward along the left margin of the esophagus. At the root of
the neck, it continues to ascend along the left margin of the esophagus
until it reaches the level of the transverse process of the seventh
cervical vertebra. Here, it bends laterally behind the carotid sheath.
On reaching the medial border of the scalenus anterior, it turns
downward and drains into the beginning of the left brachiocephalic
vein. It may, however, end in the terminal part of the subclavian or
internal jugular veins.
Main Nerves of the Neck
Cervical Plexus
The cervical plexus is fanned by the anterior rami of the first four
cervical nerves. The rami are joined by connecting branches,
which form loops that lie in front of the origins of the levator
scapulae and the scalenus medius muscles. The plexus is covered
in front by the prevertebral layer of deep cervical fascia and is
related to the internal jugular vein within the carotid sheath. The
cervical plexus supplies the skin and the muscles of the head, the
neck, and the shoulders.
Branches
Cutaneous branches
The lesser occipital nerve (C2), which supplies the back of the scalp
and the auricle
The greater auricular nerve (C2 and 3): which supplies the skin over
the angle of the mandible
The transverse cervical nerve (C2 and 3): which supplies the skin over
the front of the neck
The supraclavicular nerves (C3 and 4): The medial ,and intermediate,
and lateral branches supply the skin over the shoulder region.
Muscular branches to the neck muscles:
Prevertebral muscles, sternocleidomastoid (proprioceptive, C2 and 3),
levator scapulae (C3 and 4), and trapezius (proprioceptive, C3 and 4). A
branch from C1 joins the hypoglossal nerve. Some of these Cl fibers
later leave the hypoglossal as the descending branch, which unites with
the descending cervical nerve (C2 and 3), to form the ansa cervicalis.
The first, second, and third cervical nerve fibers within the ansa
cervicalis supply the omohyoid, stemohyoid, and stemothyroid muscles.
Other Cl fibers within the hypoglossal nerve leave it as the nerve to the
thyrohyoid and geniohyoid .
Muscular branch to the diaphragm. Phrenic nerve
Phrenic Nerve
The phrenic nerve arises in the neck from the 3rd, 4th, and 5th cervical
nerves of the cervical plexus. It runs vertically downward across the
front of the scalenus anterior muscle and enters the thorax by passing
in front of the subclavian artery .The phrenic nerve is the only motor
nerve supply to the diaphragm. It also sends sensory branches to the
pericardium, the mediastinal parietal pleura, and the pleura and
peritoneum covering the upper and lower surfaces of the central part
of the diaphragm.
Brachial Plexus
The brachial plexus is formed in the posterior triangle of the neck by
the union of the anterior rami of the 5th, 6th, 7th, and 8th cervical and
the first thoracic spinal nerves. This plexus is divided into roots,
trunks, divisions, and cords. The roots of C5 and 6 unite to form the
upper trunk, the root of C7 continues as the middle trunk, and the
roots ofC8 and T1 unite to form the lower trunk.
Each trunk then divides into anterior and posterior divisions. The
anterior divisions of the upper and middle trunks unite to form the
lateral cord, the anterior division of the lower trunk continues as the
medial cord, and the posterior divisions of all three trunks join to form
the posterior cord.
The roots of the brachial plexus enter the base of the neck between the
scalenus anterior and the scalenus medius muscles. The trunks and
divisions cross the posterior triangle of the neck, and the cords
become arranged around the axillary artery in the axilla. Here, the
brachial plexus and the axillary artery and vein are enclosed in the
axillary sheath.
• The Autonomic Nervous System in the Head and Neck
• Cervical Part of the Sympathetic Trunk
• The cervical part of the sympathetic trunk extends upward to the
base of the skull and below to the neck of the 1 st rib, where it
becomes continuous with the thoracic part of the sympathetic trunk.
It lies directly behind the internal and common carotid arteries (i.e.,
medial to the vagus) and is embedded in deep fascia between the
carotid sheath and the prevertebral layer of deep fascia. The
sympathetic trunk possesses three ganglia: the superior, middle,
and inferior cervical ganglia.
The superior cervical ganglion lies immediately below the skull.
Branches :
1. The internal carotid nerve, consisting of postganglionic fibers,
accompanies the internal carotid artery into the carotid canal in the
temporal bone. It divides into branches around the artery to form the
internal carotid plexus.
2. Gray rami communicantes to the upper four anterior rami of the
cervical nerves
• 3. Arterial branches to the common and external carotid arteries.
These branches form a plexus around the arteries and are
distributed along the branches of the external carotid artery.
• 4. Cranial nerve branches, which join the 9th, 1Oth, and 12th cranial
nerves
• 5. Pharyngeal branches, which unite with the pharyngeal branches
of the glossopharyngeal and vagus nerves to form the pharyngeal
plexus
• 6. The superior cardiac branch, which descends in the neck and
ends in the cardiac plexus in the thorax
• The middle cervical ganglion lies at the level of the cricoids cartilage.
• Branches :
• 1. Gray rami communicantes to the anterior rami of the 5th and 6th
cervical nerves
• 2. Thyroid branches, which pass along the inferior thyroid artery to the
thyroid gland
• 3. The middle cardiac branch, which descends in the neck and ends in
the cardiac plexus in the thorax
The inferior cervical ganglion in most people is fused with the first
thoracic ganglion to form the stellate ganglion. It lies in the interval
between the transverse process of the 7th cervical vertebra and the
neck of the 1st rib, behind the vertebral artery.
Branches :
1 Gray rami communicantes to the anterior rami of the 7th and 8th
cervical nerves
2. Arterial branches to the subclavian and vertebral arteries
3. The inferior cardiac branch, which descends to join the cardiac
plexus in the thorax
The part of the sympathetic trunk connecting the middle cervical
ganglion to the inferior or stellate ganglion is represented by two or
more nerve bundles .the most anterior bundle crosses in front of the
first part of the subclavian artery and then turns upward behind it. This
anterior bundle is referred to as the ansa subclavia..
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