Download Thoracic Sympathetic Trunk, Phrenic Nerves, Vagus Nerve, Azygous

Thoracic Sympathetic
Trunk, Phrenic Nerves,
Vagus Nerve, Azygous System
&
Thoracic Duct
Learning Objectives
At the end of the lecture, the student should be able to:
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Discuss the thoracic part of sympathetic chain, ganglia, course and branches.
Describe the origin, course and braches of Vagus nerves.
Describe the origin, course and braches of Phrenic nerves.
Describe formation, course, and termination of Azygous, Homozygous and
Accessory Hemiazygous Veins
Discuss their area of drainage and Tributaries.
Discuss Formation, Course and Termination of Thoracic Duct.
Describe the area of drainage of Thoracic Duct.
Sympathetic Trunks
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An important component of sympathetic part of autonomic division
of PNS.
considered a component of posterior mediastinum as
they pass through thorax.
This portion consists of two parallel cords punctuated by
11 or 12 ganglia
Thoracic sympathetic ganglia are connected to adjacent
thoracic spinal nerves by white and gray rami
communicates.
Numbered according to thoracic spinal nerve with which
they are associated.
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THORACIC SYMPATHETIC CHAIN
Lies against neck of ribs and costovertebral junctions.
12 thoracic ganglia pairs
First one often fused with inferior cervical ganglion
Referred to as stellate ganglion collectively.
THORACIC SYMPATHETIC CHAIN
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Cervical ganglia:
Superior.
Middle.
Inferior.
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THORACIC SYMPATHETIC CHAIN
The preganglionic sympathetic supply to the thoracic viscera is
from T1–5.
The postganglionic supply is from:
Superior, middle, and inferior cervical
ganglia.
T1-T5 paravertebral ganglia.
They exit the chain as direct fibers and travel downwards to enter
the thorax as cardiopulmonary splanchnic nerves.
Course of Sympathetic Trunk in Thorax
In superior portion of posterior mediastinum, trunks
are anterior to the neck of ribs.
Inferiorly, become more medial in position until they lie
on lateral aspect of vertebral bodies.
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Sympathetic trunks leave thorax by passing
posterior to diaphragm under medial arcuate
ligament or through crura of diaphragm.
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Trunks are covered by parietal pleura throughout
their course.
Branches of Sympathetic Trunk
Two types of medial branches are given off by ganglia:
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First type includes branches from the upper five ganglia;
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Second type includes branches from the lower seven ganglia.
Branches from upper part of Sympathetic Trunk
First type:
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Branches from upper five ganglia.
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Consists mainly of postganglionic sympathetic
fibers, which supply various thoracic viscera.
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Relatively small branches,
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Contain visceral afferent fibers.
Second type:
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Includes branches from lower seven ganglia.
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Consists mainly of preganglionic sympathetic
fibers, which supply the various abdominal and
pelvic viscera.
Branches from Lower part of Sympathetic Trunk
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These are Large.
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Carry visceral afferent fibers.
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Form three thoracic splanchnic nerves referred to as:
 Greater splanchnic nerve
 Lesser splanchnic nerve
 Least splanchnic nerve
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Greater Splanchnic Nerve
Arises from fifth to ninth or tenth thoracic ganglia on each side .
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Descends across vertebral bodies moving in a medial direction.
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Passes into abdomen through crus of diaphragm.
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Ends in the celiac ganglion.
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Lesser Splanchnic Nerve
Arises from ninth and tenth, or tenth and eleventh
thoracic ganglia.
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Descends across vertebral bodies moving in a medial
direction.
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Passes into abdomen through the crus of diaphragm to
end in aorticorenal ganglion.
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Lowest Splanchnic Nerve
Arises from twelfth thoracic ganglion.
Descends and passes into abdomen
through crus of diaphragm to end in
renal plexus.
THORACIC SYMPATHETIC CHAIN
The cardiopulmonary splanchnic nerves travel on their own and
do not accompany other nerves or vessels.
Function:
Coronary artery dilation.
Increase heart rate.
Bronchodilation.
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Formation of Thoracic Duct
principal channel through which lymph from most of the body is
returned to the venous system.
It begins as a confluence of lymph trunks in the abdomen,
sometimes forming a saccular dilation referred to as the cisterna
chyli (chyle cistern), which drains the abdominal viscera and walls,
pelvis, perineum, and lower limbs.
Course of Thoracic Duct
extends from vertebra LII to the root of the neck.
Entering the thorax, posterior to the aorta,
through the aortic hiatus of the diaphragm, the
thoracic duct ascends through the posterior
mediastinum to the right of midline between the
thoracic aorta on the left and the azygos vein on
the right.
lies posterior to the diaphragm and the
esophagus and anterior to the bodies of the
vertebra.
At vertebral level TV, the thoracic duct moves to
the left of the midline and enters the superior
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mediastinum.
It continues through the superior mediastinum and into the neck.
LEFT THORACIC DUCT
Receives lymph from left internal jugular lymph trunk.
Receives lymph from left subclavian lymph trunk.
Empties into venous system at junction of:
Left internal jugular vein.
Left subclavian vein.
Termination of Thoracic Duct
It terminates by joining the left brachiocephalic vein in the angle between
left Internal jugular vein and left subclavian vein
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RIGHT THORACIC DUCT
Drains upper right thoracic cavity, right upper extremity, and right
side of head and neck.
Empties into venous system at junction of:
Right internal jugular vein.
Right subclavian vein.
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LEFT THORACIC DUCT
Arises from cisterna chyl at union of right and left lumbar trunks.
Begins on front of vertebral body T12 or L1.
Runs up through the thorax along the front of the vertebral
column.
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LEFT THORACIC DUCT
At first it lies to the right of midline.
It moves over to the left side when it reaches level T-5.
Receives most of lymph from body below diaphragm.
Drains left side of thoracic cavity and part of right.
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Area of Drainage of Thoracic Duct
Thoracic Duct usually receives the contents from:
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Both the lower limb
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Confluence of lymph trunks in the
abdomen;
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Descending thoracic lymph trunks
draining the lower six or seven
intercostal spaces on both sides;
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Upper intercostal lymph trunks
draining the upper left five or six
intercostal spaces
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Ducts from posterior mediastinal
nodes;
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Ducts from posterior diaphragmatic
nodes.
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Vagus Nerves [X]
Pass through superior and posterior divisions of mediastinum on
their way to abdominal cavity.
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As they pass through the thorax, provide
parasympathetic innervation to thoracic
viscera.
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Carry visceral afferents from thoracic
viscera.
Right Vagus Nerve
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Enters the superior mediastinum.
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Lies between right brachiocephalic
vein. and brachiocephalic trunk.
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Descends in a posterior direction
toward trachea, crosses the lateral
surface of the trachea.
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Passes posteriorly to the root of right
lung to reach esophagus.
As it passes through superior mediastinum,
it gives branches to the:
 esophagus,
 cardiac plexus, and
 pulmonary plexus.
Left Vagus Nerve
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It enters superior mediastinum posterior to left brachiocephalic
vein and between the left common carotid and left subclavian arteries.
As it passes into the superior mediastinum, it lies just deep to the
mediastinal part of the parietal pleura and crosses the left side of
the arch of aorta. it gives branches to:
Esophagus,
Cardiac plexus, and
Pulmonary plexus.
Also gives rise to the left recurrent laryngeal nerve
It continues to descend in a posterior direction .
Passes posterior to root of left lung to reach esophagus in posterior
mediastinum
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Left Recurrent Laryngeal Nerve
Branch of left vagus nerve.
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After origin, it passes at inferior margin of arch of aorta
just lateral to ligamentum arteriosum.
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Passes inferior to arch of aorta before ascending on its
medial surface.
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Entering a groove between the trachea and esophagus,
the left recurrent laryngeal nerve continues superiorly to
enter the neck and terminate in the larynx
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Phrenic Nerves
Arise in cervical region mainly from fourth, but also from third and
fifth cervical spinal cord segments.
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Phrenic nerves descend through thorax to supply motor and sensory
innervation to diaphragm and its associated membranes.
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Provide innervation through somatic afferent fibers to the mediastinal
pleura, fibrous pericardium, and parietal layer of serous pericardium.
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Right Phrenic Nerve
Enters superior mediastinum lateral to right vagus nerve.
Lateral and slightly posterior to beginning of the right brachiocephalic
vein. It continues inferiorly along the right side of this vein and the right
side of the superior vena cava.
On entering middle mediastinum, right phrenic nerve descends along
right side of pericardial sac, within the fibrous pericardium, anterior to
the root of the right lung.
The pericardiacophrenic vessels accompany it through most of its
course in the thorax.
Leaves thorax by passing through diaphragm with inferior vena cava.
Paralysis of Left Recurrent Laryngeal Nerve
Branch of left vagus nerve.
Passes between pulmonary artery and aorta, a region known clinically
as aortopulmonary window.
May be compressed in any patient presenting with a pathologic mass
in this region.
This compression results in vocal cord paralysis and hoarseness of
the voice.
Lymph node enlargement, often associated with spread of lung cancer,
is a common condition that may produce compression.
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Chest radiography is therefore usually carried out for all patients who
present with a hoarse.
Paralysis of Right Recurrent Laryngeal Nerve
More superiorly, the right vagus nerve gives off the right recurrent laryngeal
nerve which 'hooks' around the right subclavian artery at the superior
sulcus of the right lung.
If a patient presents with a hoarse voice and a right vocal cord palsy is
demonstrated at laryngoscopy, chest radiography with an apical
lordotic view should be obtained to assess for cancer in the right lung
apex (Pancoast's tumor).
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Left Phrenic Nerve
Enters superior mediastinum in a position similar to path taken by right
phrenic nerve.
Lies lateral to left vagus nerve and lateral and slightly posterior to
beginning of left brachiocephalic vein.
Continues to descend across left lateral surface of arch of aorta,
passing superficially to the left vagus nerve and left superior intercostal
vein.
On entering the middle mediastinum, left phrenic nerve follows left side
of pericardial sac, within the fibrous pericardium, anterior to root of left
lung.
Accompanied by pericardiacophrenic vessels.
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Leaves thorax by piercing diaphragm near the apex of heart.
Esophageal Plexus
After passing posteriorly to root of lungs,
right and left vagus nerves approach
esophagus.
each nerve divides into several branches
that spread over this structure, forming the
esophageal plexus. There is some mixing
of fibers from the two vagus nerves as the
plexus continues inferiorly on the
esophagus toward the diaphragm. Just
above the diaphragm, fibers of the plexus
converge to form two trunks:
Esophageal Plexus
Anterior vagal trunk on the anterior surface of the esophagus, mainly
from fibers originally in the left vagus nerve
Posterior vagal trunk on the posterior surface of the esophagus, mainly
from fibers originally in the right vagus nerve.
The vagal trunks continue on the surface of the esophagus as it passes
through the diaphragm into the abdomen.
References
GRAYS ANATOMY FOR STUDENTS 2004, -by Richard Drake, Wayne
Vogl, Adam W.M. Mitchell
GRANT'S.ATLAS.OF.ANATOMY.12th. Anne M. R. Ager and Arther F.
Delly
MOORE, KEITH L. - CLINICALLY ORIENTED ANATOMY, and Keith L.
Moore
by Keith L. Moore
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