Mediastinum 3 (Grace's)

Question 1

Thoracic Duct

Answer 1

largest lymphatic channel in the body

• in posterior mediastinum
• on anterior aspect of T5-T12 bodies

Question 2

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

In which areas does this occur?

Answer 2

• the lower limbs
• pelvic cavity
• abdominal cavity
• left upper limb
• left side of the thorax, head, and neck

(all but the right superior quadrant)

Question 3

thoracic duct originates from ___________

and ascends through _____________.

Answer 3

** **1. chyle cistern (cisterna chyli) in the abdomen

2. aortic hiatus in the diaphragm

Question 4

structure of the thoracic duct?

Answer 4

• thin walled
• dull white/colorless
• often ‘beaded’ because of its numerous valves

Question 5

Where is the thoracic duct positioned in the posterior mediastinum?

(in regards to other structures)

Answer 5

• thoracic aorta on its left
• the azygos vein on its right
• the esophagus anteriorly
• the vertebral bodies posteriorly

Question 6

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

At what vertebral level does this occur?

Answer 6

T4, T5, or T6 vertebra

Question 7

The thoracic duct receives branches from…?

Answer 7

• middle & superior intercostal spaces (Right & Left)
• posterior mediastinal structres

Question 8

Near the termination of the thoracic duct, it often receives

the _____________, _________________ and ________________ lymphatic trunks.

Answer 8

• jugular lymphatic trunk
• subclavian lymphatic trunk
• bronchomediastinal lymphatic trunk

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

Question 9

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

Answer 9

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)

Question 10

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

Answer 10

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

Question 11

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

Answer 11

Rates range from 75 to 200 mL per hour.

Question 12

What is “chylothorax”?

Answer 12

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)

Question 13

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

Answer 13

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

Question 14

variations of the thoracic duct are…

Answer 14

common!

sometimes 2 thoracic ducts are present for a short distance

Question 15

posterior mediastinal lymph nodes lie ________________?

Answer 15

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.

Question 16

posterior mediastinal lymph nodes receive lymph from ….

Answer 16

• esophagus
• posterior aspect of the pericardium and diaphragm
• middle posterior intercostal spaces

Question 17

posterior mediastinal lymph nodes drain to ….

Answer 17

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

Question 18

Azygos system of veins:

• location?
• what does it drain?

Answer 18

1. on each side of the vertebral column

2. drains the:

- back

**- **thoracoabdominal walls

- mediastinal viscera

Question 19

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

Answer 19

the AZYGOS system

Question 20

the azygos vein is formed by what union?

Answer 20

ascending lumbar veins + right subcostal veins

(level of T12)

Question 21

1. Between which 2 structures does the azygos veiin form a pathway?
2. Where does this drain blood from?

Answer 21

1. superior vena cava + inferior vena cava
2. drains blood from the posterior walls of the thorax + abdomen

Question 22

Where does the azygos vein asend?

Which vertebrae does it pass?

Answer 22

ascends in the posterior mediastinum

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

Question 23

The azygos vein arches over ________________________

to join the_______________.

Answer 23

1. the superior aspect of the root of the right lung
2. superior vena cava

Question 25

The azygos vein communicates with which venous plexus?

What does this drain?

What other veins does it receive?

Answer 25

1. vertebral venous plexuses
2. drain the back, vertebrae, and structures in vertebral canal
3. also receives the mediastinal, esophageal, and bronchial veins

Question 26

**Hemiazygus vein...**

Answer 26

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

Question 27

hemiazygos vein ascends the \_\_\_\_\_\_\_ side of the vertabral column, posterior to the ____________ as far as the _____ vertebrae.

Answer 27

1. Left 2. thoracic artery 3. T9 vertebra

Question 28

At T9 the hemiazygos vein it crosses to the\_\_\_\_\_\_\_\_ side, posterior to the \_\_\_\_\_\_\_\_\_\_\_\_, \_\_\_\_\_\_\_\_\_\_\_\_\_\_, and \_\_\_\_\_\_\_\_\_\_\_. It joins the \_\_\_\_\_\_\_\_vein.

Answer 28

1. Right 2. aorta, thoracic duct, esophagus 3. azygos vein

Question 29

hemiazygos vein receives the _______________________ veins, the _____________ veins, and ________________ veins.

Answer 29

1. inferior three posterior intercostal veins 2. inferior esophageal veins 3. several small mediastinal veins

Question 30

At that intercostal space does the **accessory hemiazygos vein** begin at? Where does it descend?

Answer 30

1. medial end of the **4th or 5th intercostal space** 2. descends on the left side of the vertebral column from **T5 through T8**

Question 31

The **accessory hemiazygos vein** receives tributaries for where?

Answer 31

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

Question 32

Where does the accessory hemiazygos vein join the azygos vein?

Answer 32

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

Question 33

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

Answer 33

accessory hemiazygos vein + hemiazygos vein

Question 34

The accessory hemiazygos is frequently connected to what other vein?

Answer 34

left superior intercostal vein

Question 35

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

Answer 35

1st - 3rd intecostal spaces

Question 36

which vein does the left superior intercostal vein usually drain into? (not the accessory hemiazygos)

Answer 36

left brachiocephalic vein

Question 37

when obstruction occurs in the inferior vena cave, how does venous drainage get to the heart? (from the thoracic, abdominal, & back regions)

Answer 37

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

Question 38

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

Answer 38

an **accessory azygos vein ** | (others have no hemiazygos vein system)

Question 39

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

Answer 39

when the azygos system receives all the blood from the inferior vena cava **except that from the liver** ## Footnote *(In these people, the azygos system drains nearly all the blood inferior to the diaphragm, except from the digestive tract)*

Question 40

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

Answer 40

... 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**

Question 41

What forms a major part of the autonomic nervous system? (think within the thoracic region)

Answer 41

**sympathetic trunks** and their **associated ganglia **

Question 42

the **thoracic sympathetic trunks** are in continuity with \_\_\_\_\_\_\_\_\_\_\_\_\_?

Answer 42

cervical and lumbar sympathetic trunks

Question 43

The thoracic sympathetic trunks lie against \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_, \_\_\_\_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_?

Answer 43

- 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

Question 44

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

Answer 44

- greater splanchnic nerve - lesser splanchnic nerve - least splanchnic nerve

Question 45

Lower thoracic splanchnic nerver are part of the ___________________ nerves because they supply \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.

Answer 45

1. abdominopelvis splanchnic nerves 2. supply viscera inferior to the diaphragm

Question 46

The lower thoracic splanchnic nerves consist of ____________ fibers? From which sympathetic ganglia?

Answer 46

1. presynaptic fibers 2. 5th - 12th sympathetic ganglia

Question 47

Where do lower thoracic splanchnic nerves pass through? Where do they synapse?

Answer 47

1. pass through the **diaphragm** 2. synapse in **prevertabal ganglia **in the abdomen

Question 48

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

Answer 48

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

Question 49

Which 3 plexuses are present in the mediastinum?

Answer 49

- cardiac plexus - pulmonary plexus - esophageal plexus