Download Thoracic Sympathetic Trunk

LECTURE OUTLINE
Thoracic Sympathetic Trunk,
Learning Objectives:
•At the end of the lecture, the student should be able to:
•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
•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.
•Sympathetic trunks leave thorax by passing posterior to diaphragm
under medial arcuate ligament or through crura of diaphragm.
•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.
•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:
•Esophagus,
•Cardiac plexus, and
•Pulmonary plexus.
Left Vagus Nerve
•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 pericardiaco-phrenic 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.
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
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
•Leaves
by pericardiacophrenic vessels.
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.
•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.
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
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:
•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:
•Fourth to eighth left posterior intercostal veins;
•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
•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:
•Both the lower limb
•Confluence of lymph trunks in the abdomen;
•Descending thoracic lymph trunks draining the lower six or seven
intercostal spaces on both sides;
•Upper intercostal lymph trunks draining the upper left five or six
intercostal spaces
•Ducts from posterior mediastinal nodes;
•Ducts from posterior diaphragmatic nodes.