Mediastinum 3 Flashcards
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
- 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…
common!
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?
- 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