Download Thoracic Sympathetic Trunk, Phrenic Nerves, Vagus Nerve

Thoracic Sympathetic
Trunk, Phrenic Nerves,
Vagus Nerve &
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.
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.
Usually 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.
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:
• First type includes branches from the
upper five ganglia;
• Second type includes branches from
the lower seven ganglia.
Branches from upper part of Sympathetic Trunk
First type:
• Branches from upper five ganglia.
• Consists mainly of postganglionic
sympathetic fibers, which supply various
thoracic viscera.
• Relatively small branches,
• Contain visceral afferent fibers.
Second type:
• Includes branches from lower seven
ganglia.
• Consists mainly of preganglionic
sympathetic fibers, which supply the various abdominal and pelvic viscera.
Branches from Lower part of Sympathetic Trunk
• These are Large.
• Carry visceral afferent fibers.
• Form three thoracic splanchnic nerves
referred to as:
Greater splanchnic nerve
Lesser splanchnic nerve
Least splanchnic nerve
Greater Splanchnic Nerve
• Arises from fifth to ninth or tenth
thoracic ganglia on each side .
• Descends across vertebral bodies
moving in a medial direction.
• Passes into abdomen through crus
of diaphragm.
• Ends in the celiac ganglion.
Lesser Splanchnic Nerve
• Arises from ninth and tenth, or tenth
and eleventh thoracic ganglia.
• Descends across vertebral bodies
moving in a medial direction.
• Passes into abdomen through the crus
of diaphragm to end in aorticorenal
ganglion.
Lowest Splanchnic Nerve
• Arises from twelfth thoracic ganglion.
• Descends and passes into abdomen through crus of diaphragm to end in
Renal plexus.
Vagus Nerves [X]
• Pass through superior and
posterior divisions of
mediastinum on their way to
abdominal cavity.
• As they pass through the thorax,
provide parasympathetic
innervation to thoracic viscera.
• Carry visceral afferents from
thoracic viscera.
Right Vagus Nerve
Enters the superior mediastinum.
Lies between right brachiocephalic vein. and
brachiocephalic trunk.
• Descends in a posterior direction toward
trachea, crosses the lateral surface of the
trachea.
• Passes posteriorly to the root of right lung to
reach esophagus.
As it passes through superior mediastinum, it gives branches to the:
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 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
Left Recurrent Laryngeal Nerve
• Branch of left vagus nerve.
• After origin, it passes at inferior margin of arch of aorta just
lateral to ligamentum arteriosum.
• Passes inferior to arch of aorta before ascending on its
medial surface.
• Entering a groove between the trachea and esophagus, the
left recurrent laryngeal nerve continues superiorly to enter
the neck and terminate in the larynx
Phrenic Nerves
• arise in cervical region mainly from fourth, but also
from third and fifth cervical spinal cord segments.
• Phrenic nerves descend through thorax to supply
motor and sensory innervation to diaphragm and its
associated membranes.
• Provide innervation through somatic afferent fibers
to the mediastinal pleura, fibrous pericardium, and
parietal layer of serous pericardium.
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.
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Paralysis of Left Recurrent Laryngeal Nerve
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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.
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 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).
Left Phrenic Nerve
• Enters superior mediastinum in a position similar to path taken by
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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.
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:
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.
Azygos system of veins
The Azygos system of veins consists of a series of
longitudinal vessels on each side of the body that
drain blood from the body wall and move it
superiorly to empty into the superior vena cava.
• Blood from some of the thoracic viscera also enter
into the azygos system, and there are anastomotic
connections between azygos and other systemic
abdominal veins
The Azygos system of veins serves as an important
anastomotic pathway capable of returning venous
blood from the lower part of the body to the heart if
the inferior vena cava is blocked. The major veins in
the system are:
Azygos vein, on the right; and
Hemiazygos vein and
Accessory Hemiazygos vein, on the left.
There is significant variation in the origin, course,
tributaries, anastomoses, and termination of these
vessels.
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Azygos vein
Formation
• The Azygos vein arises opposite vertebra L1 or L2 by the junction of the Right
Ascending Lumbar Vein and the Right Subcostal Vein. It may also arise as a direct
branch of the inferior vena cava, which is joined by a common trunk from the
junction of the right ascending lumbar vein and the right Subcostal vein
Course
• The azygos vein enters the thorax through the aortic hiatus of the diaphragm, or it
enters through or posterior to the right crus of the diaphragm. It ascends through the
posterior mediastinum, usually to the right of the thoracic duct.
Termination of Azygos Vein
At approximately vertebral level T6, it arches anteriorly,
over the root of the right lung, and terminates by
joining the superior vena cava at the level of
approximately T4 before the superior vena cava enters
the pericardial sac.
Tributaries
Tributaries of the azygos vein include:
• Right superior intercostal vein
A single vessel formed by the junction of the second,
third, and fourth intercostal veins
• Fifth to Eleventh right posterior intercostal veins,
• Hemiazygos vein,
• Accessory hemiazygos vein,
• Esophageal veins,
• Mediastinal veins,
• Pericardial veins, and
• Right bronchial veins.
Formation Hemiazygos Vein
• The hemiazygos vein (inferior
hemiazygos vein) usually arises at the
junction between the left ascending
lumbar vein and the left subcostal
vein. It may also arise from either of
these veins alone and often has a
connection to the left renal vein.
• Course
The hemiazygos vein usually enters the
thorax through the left crus of the
diaphragm, but may enter through the
aortic hiatus. It ascends through the
posterior mediastinum, on the left side of
vertebral column.
Hemiazygous Vein
TERMINATION
At approximately vertebral level T9, it crosses the vertebral column, posterior to the
thoracic aorta, esophagus, and thoracic duct, to enter the azygos vein.
TRIBUTARIES:
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Lowest four or five left posterior intercostal veins
Esophageal veins
Mediastinal veins
Formation Accessory hemiazygos vein
The accessory hemiazygos vein (superior
hemiazygos vein) descends on the left side from the
superior portion of the posterior mediastinum to
approximately vertebral level T8. At this point, it
crosses the vertebral column to join the azygos vein,
or ends in the hemiazygos vein, or has a connection
to both veins.
TRIBUTARIES
Usually, it also has a connection superiorly to the left
superior intercostal vein.
Vessels that drain into the accessory hemiazygos vein include:
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Fourth to eighth left posterior intercostal veins;
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Sometimes, the left bronchial veins.
Formation of Thoracic Duct
The thoracic duct is the 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
The 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.
It 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 mediastinum. It continues
through the superior mediastinum
and into the
neck.
Termination of Thoracic Duct
It terminates by joining the left brachiocephalic vein in the angle between left internal
jugular vein and left subclavian vein.
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.
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, by Keith L. Moore and Keith L.
Moore