Posterior Mediastinum.docx

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Define the boundaries of posterior mediastinum

The major boundaries of the posterior mediastinum are:

Angle of Louis for superior portion

T5-T12 for the posterior portion

The posterior diaphragm for the inferior portion

And the Mediastinal cavity as the anterior portion

Describe and relate structures found in the posterior mediastinum (i.e., descending aorta, esophagus,

major veins, thoracic duct, splanchnic, sympathetic nerve and vagus nerves)

S

Structures in PM

1. Esophagus

2. Thoracic aorta / Descending aorta

3. Azygos venous system

i. Azygosii. Hemiazygosiii. Accessory hemiazygos

4. Thoracic duct

5. Sympathetic nerve

i. Sympathetic trunkii. Splanchnic nerve6. Vagus nerve



Posterior Mediastinal Structures



Aortic Arch

Begins at left of T4

Descends from T5-T12

Posterior to root of LeftLung, Esophagus, Pericardium

Most inferior portion – Midline displacing esophagus

Branches

o Anterior Unpaired (A)

Branch to Gut

Pericardial Branch

Mediastinal Arteries

o Lateral Paired (B)

Bronchial arteries and other visceral organs

Not gut

o Posterior Unpaired (C)

3-11 posterior intercostal

Rt. Posterior Intercostal is longer b/c they pass over vertebral bodies

1 subcostal art -> diaphragm

Sympathetic

trunk

Hemiazygos

Thoracic

aorta/Descending

aorta

Great splanchnic

n.

Vagus n.

Azygos v.

Esophagus

Thoracic duct

Great

splanchnic

n.

Right Left View: Left Right View:

Thoracic

duct

Azygos

vein

i i li i l i

i li l i

i i l i

l li

Posterior intercostal

arteries



Esophagus:

Posterior and left of atrium

Main posterior part of heart

Once cut into diaphragm, deviates to the left

Exits Esophagus Hiatus at T10 w/ anterior and posterior Vagal trunks

Anastomosis

Rt. posteriorintercostal arteries arelonger than the leftones: because they

pass over the

vertebral bodies .Thoracic aortaruns along theleft side ofvertebral bodie

3rd -11th Posterior intercostal arteries

pericardium



Thoracic Duct:

Largest Lymph Channel

Empty at Left Venous Angle (union of left Jugular and Subclavian Vein)

Origin: Chyle Cistern @ L2

Ascends on right side of T5-T12

Left of Azygus

Right of Thoracic Aorta

Posterior to Esophagus

Crosses to the left of sternal angle

Right Lymphatic Duct:

Enters at right Venous Angle

Drains upper right quadrant of body

Azygos Vein:

“ The duck b tween t w o gooses (duck =

thoracic duct) 2 gooses = azyGOUS and

esophaGOUS”

As viewed from

the feet

Thoracic duct

Chyle cistern

Lt. venous

angle

Thoracic aorta

Azygos v.

Azygos

vein

SVC

Accessory

hemiazygos



Drains:

o Back

o Thoracoabdominal Wall

o Mediastinal Viscera

Collateral Circulation with IVC and SVC

Arch over root of right lung -> join with SVC

Left Azygus Equivalents

1st Posterior Intercostal veins

o Drains into Brachiocephalic veins

Left superior intercostal vein (A)

o Drain 2nd-4th intercostal space

o Drains into left Brachiocephalic vein

Accessory Hemiazygos (B)

o Drains left 5th-8th intercostal Veins

o May drain into left bronchial vein

o Crosses to right side at T7/T8 to drain into Azygos

Hemiazygos (C)

o Drains 9th-12th intercostal space

o Crosses to right side at T9 to drain into Azygos

Nerves in Posterior Mediastinum:

Sympathetic Trunk

Splanchnic Nerves

Vagus (Esophageal plexus)

Sympathetic Trunk:

Lt. &

Renal

Ascen

lumba

Azygos



Splanchnic Nerves:

Splanchnic = Visceral = Internal organs

Sympathetic trunk

Splanchnic

nerve

Options followed by sympathetic nerves:1- enter chain, synapse and exit at same level2- enter chain, ascend or descend to synapse3- enter chain and pass through to prevertebral Ganglia splanchnic nerve



Contains presympathetic fibers to abdominal organs

At T10 is the Diaphragmatic Hiatus.

T12 is under the Diaphragm

Esophageal Vagal Plexus:

a) Greater splanchnic T5 - T9

b) Lesser splanchnic T10 - T11c) Least splanchnic T12

Greater splanchnic n.

Lesser splanchnic n.Least splanchnic n.

Intercostal n.

Sympathetic trunk

Greater splanchnic n. T5-T9

Fibers to Lesser splanchnic n.

T10-11

-Least splanchnic n. T12(inferior to diaphragm)

Sympathetic trunk

Paravertebral ganglia

Vagus n.

Phrenic n.



Collection of:

o POSTsynaptic sympathetic fibers

o PREsynaptic parasympathetic fibers

o Visceral Afferent

Due to embryological development, there is a twisting in the Gut tube. Causing the Left

Vagus Nerve to be turned Anteriorly and the Right Vagus Nerve to be turned Posteriorly.

o Mnemonic: LARP – Left becomes Anterior, Right become Posterior

Diaphragm:

Anterior vagal trunk

(Vagus nerve)

Left vagus nerve

Esophageal plexus

Exit Thoracic cavity

via Esophageal

hiatus at T10

90° embryologic rotation



Right phrenic

Inferior cavopeningEsophageal

opening

Aorticopening

Left phrenic n.

Pericardialsac

Azygosvein

Central tendon

Splanchni

nerves



Mnemonic: I Ate 10 Eggs AAT 12

o I Ate – Inferior Vena Cava, T8

o 10 Eggs – T10, Esophagus, Vagus, Left inferior Phrenic Vessels

o AAT 12 – Aorta, Azygos v, Thoracic duct

Opening Vert. level Location Structures passing through

Vena caval

hiatus

T8 Central tendon of

diaphragm

Inferior Vena Cava

Rt. phrenic n.

Esophageal

hiatus

T10 Muscular part at the

right crus of the

diaphragm

Esophagus

Vagus nerve,

Left inferior phrenic vessels,

Aortic hiatus T12 Between the

diaphragm and

vertebral column

Aorta

Azygos v.

Thoracic duct

Diaphragmatic openings I Ate 10 Eggs AAT 12



Explain the manifestations and clinical significance of the following: esophageal constrictions, esophageal

diverticula, laceration of thoracic duct and Troisier’s sign, thoracic aortic aneurysm, SVC obstruction,

paradoxical motion of diaphragm, swollen rt. superior tracheobronchial nodes

(CR) Thoracic Aortic Aneurysm

Aneurysm that causes separation of the Tunica Intimia And Tunica Media

Risk Factors



o Atherosclerosis

o Connective tissue disorder

o Inflammation of Aorta

o Trauma

Internal Bleeding

(CR) Esophageal Constrictions:

Three main sites:

Left main bronchi

Aortic Arch

Diaphragmatic Esophageal Hiatus

(CR) Esophageal Diverticula

Parabrochial Diverticulum (outside)

“True” traction diverticula

Protrusion of all layers (not a weak spot)

Pulling force from outside

Cause: Tumor

Epipherenic Diverticulum

False Pulsion Diverticula

Herniation of the mucosa and submucosa through weak spots

Pushing force from inside

Causes: Neuromuscular Dysfunction (affect Vagus Nerve)

(CR) Virchow’s Node and Troisier’s Sign

Virchow’s Node

Muscular layer



Lymph Nodes in Left Supraclavicular Fossa

Troisier’s Sign

Enlargment of Virchow’s Node

GI Cancer metastasized through Thoracic Duct

(CR) Laceration of Thoracic Duct

Injured during surgery. Hard to spot

Lymph escapes and produces chylothorax

o Causes:

Trauma

Lymphoma

Family History

Premature babies

o Test Pleura for triglyceride level to eliminate pleural effusion

(CR) Azygos Vein Collateral Circulation

Supra-Azygos SVC obstruction

Distended arm and neck veins

Dilated and tortuous veins on ubber chest and back

Superior Vena Cava Syndrome

Troisier ’s sign



Infra-Azygos SVC obstruction

Dilation of collateral vessels on the anterior and posterior abdominal walls

Back flow

Rerouted to IVC



(CR) Paradoxical Motion of the Diaphragm

Hemidiaphragm supplied with separate phrenic n.

Damage to phrenic n. -> paradoxical Motion

Inspiration:

o The paralyzed dome ascends instead of descending, pushed down by abdominal

vicera

Expiration:

o Paralyzed dome descends because of lungs positive pressure.



10/15/2013 5:13:00 AM

Posterior Mediastinum.docx

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