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Thoracic Duct

largest lymphatic channel in the body

- in posterior mediastinum

- on anterior aspect of T5-T12 bodies


The thoracic duct conveys most lymph of the body to venous system.

In which areas does this occur?

- the lower limbs

- pelvic cavity

- abdominal cavity

- left upper limb

- left side of the thorax, head, and neck

(all but the right superior quadrant)


thoracic duct originates from ___________

and ascends through _____________.

 1. chyle cistern (cisterna chyli) in the abdomen

2. aortic hiatus in the diaphragm


structure of the thoracic duct?

- thin walled

- dull white/colorless

- often 'beaded' because of its numerous valves


Where is the thoracic duct positioned in the posterior mediastinum? 

(in regards to other structures)

- thoracic aorta on its left

- the azygos vein on its right 

- the esophagus anteriorly

- the vertebral bodies posteriorly


The thoracic duct crosses to the left (posterior to the esophagus) and ascends into the superior mediastinum.

At what vertebral level does this occur?

T4, T5, or T6 vertebra


The thoracic duct receives branches from...?

- middle & superior intercostal spaces (Right & Left)

- posterior mediastinal structres


Near the termination of the thoracic duct, it often receives

the _____________, _________________ and ________________ lymphatic trunks.

jugular lymphatic trunk

- subclavian lymphatic trunk 

- bronchomediastinal lymphatic trunk 

(although any or all these vessels may terminate independently). 


Where does the thoracic duct usually empty into the venous system?

near the union of the left internal jugular and subclavian veins

(the left venous angle or origin of the left brachiocephalic vein

but it may open into the left subclavian vein)


Why is the thoracic duct vulnerable to inadvertent injury during procedures in the posterior mediastinum? 

It is difficult to see (thin walled, colorless) and can be easily lacerated


At what rate does lymph escape the thoracic duct when it is lacerated?

 Rates range from 75 to 200 mL per hour


What is "chylothorax"?

Produced when lymph/chyle from the lacteals of the intestine enter the pleural cavity

(fluid may be removed by a needle tap or by thoracentesis; in some cases it may be necessary to ligate [seal] the thoracic duct) 


How does lymph travel through the body once the thoracic duct has been sealed off after a laceration?

It returns to the venous system by other lymphatic channels that join the thoracic duct superior to the ligature.


variations of the thoracic duct are...


sometimes 2 thoracic ducts are present for a short distance


posterior mediastinal lymph nodes lie ________________?

posterior to the pericardium

(relate to the esophagus & thoracic aorta)

There are several nodes posterior to the inferior part of the esophagus and more (up to eight) anterior and lateral to it


posterior mediastinal lymph nodes receive lymph from ....

 - esophagus

- posterior aspect of the pericardium and diaphragm

- middle posterior intercostal spaces


posterior mediastinal lymph nodes drain to ....

right or left venous angles via the right lymphatic duct or the thoracic duct


Azygos system of veins:

- location?

- what does it drain?

1. on each side of the vertebral column

2. drains the:

- back

thoracoabdominal walls 

- mediastinal viscera


What venous system varies greatly in its origin, course, tribularies, and anastomoses?

the AZYGOS system


the azygos vein is formed by what union?

ascending lumbar veins + right subcostal veins

(level of T12)


1. Between which 2 structures does the azygos veiin form a pathway?

2. Where does this drain blood from?

1. superior vena cava + inferior vena cava

2. drains blood from the posterior walls of the thorax + abdomen


Where does the azygos vein asend?

Which vertebrae does it pass?

ascends in the posterior mediastinum

close to the (R. side) bodies of the inferior 8 thoracic vertebrae


The azygos vein arches over ________________________

to join the_______________.

1. the superior aspect of the root of the right lung

2.  superior vena cava


The azygos vein communicates with which venous plexus?

What does this drain?

What other veins does it receive?

1. vertebral venous plexuses 

2. drain the back, vertebrae, and structures in vertebral canal

3. also receives the mediastinal, esophageal, and bronchial veins


Hemiazygus vein...

arises on the left side by the junction of the left subcostal and ascending lumbar veins 


hemiazygos vein ascends the _______ side of the vertabral column,

posterior to the ____________ as far as the _____ vertebrae.

1. Left

2. thoracic artery

3. T9 vertebra


At T9 the hemiazygos vein it crosses to the________ side, 

posterior to the ____________, ______________, and ___________.

It joins the ________vein.

1. Right

2. aorta, thoracic duct, esophagus

3. azygos vein


hemiazygos vein receives the _______________________ veins,

the _____________ veins, and ________________ veins.

1. inferior three posterior intercostal veins

2. inferior esophageal veins

3. several small mediastinal veins


At that intercostal space does the accessory hemiazygos vein begin at?

Where does it descend?


1. medial end of the 4th or 5th intercostal space

2. descends on the left side of the vertebral column from T5 through T8 


The accessory hemiazygos vein receives tributaries for where?

the 4th - 8th intercostal spaces + sometimes the left bronchial veins


Where does the accessory hemiazygos vein join the azygos vein?

where it crosses over the T7 or T8 vertebra, posterior to the thoracic aorta and thoracic duct.


Which 2 veins sometimes join, and open together into the azygos vein?

accessory hemiazygos vein + hemiazygos vein 


The accessory hemiazygos is frequently connected to what other vein?

left superior intercostal vein


which intercostal spaces are drained by the left superior intercostal vein?

1st - 3rd intecostal spaces


which vein does the left superior intercostal vein usually drain into?

(not the accessory hemiazygos)

left brachiocephalic vein


when obstruction occurs in the inferior vena cave, how does venous drainage get to the heart? 

(from the thoracic, abdominal, & back regions)

The azygos, hemiazygos, and accessory hemiazygos veins offer alternate routes


In some people, what parallels the azygos vein on the right side?

an accessory azygos vein 

(others have no hemiazygos vein system)


What is an important (yet uncommon) clinical variation in the azygos system?

when the azygos system receives all the blood from the inferior vena cava except that from the liver

(In these people, the azygos system drains nearly all the blood inferior to the diaphragm, except from the digestive tract)


If an obstruction of the superior vena cava occurs superior to the entrance of the azygos vein....?

... blood can drain inferiorly into the veins of the abdominal wall

and return to the right atrium through the azygos venous system and

the inferior vena cava


What forms a major part of the autonomic nervous system?

(think within the thoracic region)

sympathetic trunks and their associated ganglia 


the thoracic sympathetic trunks are in continuity with _____________?

cervical and lumbar sympathetic trunks


The thoracic sympathetic trunks lie against  _______________,

___________ and _______________?

- the heads of the ribs in the superior part of the thorax

-  the costovertebral joints in the midthoracic level

-  and the sides of the vertebral bodies in the inferior part of the thorax 


What are the lower splanchnic nerves also know as? (3)

- greater splanchnic nerve

- lesser splanchnic nerve

- least splanchnic nerve


Lower thoracic splanchnic nerver are part of the ___________________ nerves

because they supply ___________________.

1. abdominopelvis splanchnic nerves

2. supply viscera inferior to the diaphragm


The lower thoracic splanchnic nerves consist of ____________ fibers?

From which sympathetic ganglia?

1. presynaptic fibers

2. 5th - 12th sympathetic ganglia


Where do lower thoracic splanchnic nerves pass through?

Where do they synapse?

1. pass through the diaphragm

2. synapse in prevertabal ganglia in the abdomen


What do the lower thoracic splanchnic nerves supply, and to where?

... supply sympathetic innervation to most of the abdominal viscera


Which 3 plexuses are present in the mediastinum?

- cardiac plexus

- pulmonary plexus

- esophageal plexus