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CRAAB 3 > Ach: Superior and Posterior Mediastinum > Flashcards

Ach: Superior and Posterior Mediastinum Flashcards

1
Q

Where is the mediastinum located?

A

Behind the posterior surface of sternum and medial to the pleural cavities

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2
Q

What are the limits of the mediastinum?

A

Upper: thoracic inlet
Lower: diaphragm
posterior boundary: vertebral bodies of T1 to T12

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3
Q

What are the boundaries of the superior mediastinum?

A

Superior to the horizontal plane passing through the sternal angle to the intervertebral disc between T4 and T5

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4
Q

What are the contents of the superior mediastinum?

A
  1. Thymus gland

2. Great vessels

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5
Q

When is the thymus gland prominent?

A

It’s prominent during infancy and is replaced by fatty CT in the adult.

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6
Q

What is the role of the thymus gland?

A

Development and maintenance of the immune system (T lymphocyte production)

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7
Q

What are the great vessels of the heart and pericardium?

A

Arteries: arch of aorta, brachiocephalic, left common carotid and left subclavian arteries

Veins: SVC, R. and L. brachiocephalic veins, termination of the azygos veins into the SVC

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8
Q

What are the contents of the superior mediastinum?

A
  1. Thymus gland
  2. Great vessels
  3. Viscera (trachea and esophagus)
  4. Nerves
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9
Q

What nerves are located in the superior mediastinum?

A
  1. R and L vagus nerves
  2. R and L recurrent laryngeal nerves
  3. Cardiac nerves
  4. R and L phrenic nerves
  5. superficial/deep cardiac plexus
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10
Q

Where do the vagus nerves descend to?

A

They descend posterior to the root of the lung.

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11
Q

Where are the R and L recurrent laryngeal nerves located?

A

RRL- loops around the subclavian a.

LRL- loops around the arch of the aorta and adjacent to the ligamentous arteriosum

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12
Q

Where are the cardiac nerves located?

A

Pre-gang/post-gang parasymp/symp headed to the cardiac plexus.

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13
Q

Where are the R and L phrenic nerves located?

A

They descend w/in the folds of the pericardial sac and anterior to the root of the lung.

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14
Q

Where are the superficial and deep cardiac plexus located?

A

superficial–lies inferior to the aortic arch.

deep- between the aorta arch and tracheal bifurcation

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15
Q

What are the boundaries of the posterior mediastinum?

A
  1. Anteriorly- fibrous pericardium and diaphragm
  2. posteriorly- T5-T12 (anterior vertebral bodies)
  3. laterally- mediastinal parietal plueura
  4. Superiorly- superior medisastinum (sternal angle, T4, T5)
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16
Q

Where does the thoracic aorta lie?

A

Extends from T4-T12 and enters the abdomen at the aortic hiatus.

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17
Q

Where do the thoracic duct and azygos vein lie in the posterior mediastinum?

A

Both lie to the right and pass through the aortic hiatus at T10.

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18
Q

What are the major branches of the thoracic aorta?

A
  1. posterior intercostal arteries (supply spaces 3-11)
  2. subcostal arteries (supply 12 space)
  3. visceral branches (esophagus, bronchi, mediastinum and pericardium)
  4. superior phrenic (to diaphragm)
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19
Q

Where does the esophagus lie?

A

It extends from C6 to T10 and enters the thorax via the superior mediastinum. It passes posterior to the left primary bronchus to enter the posterior mediastinum.

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20
Q

What part of the trachea is skeletal muscle vs. smooth muscle?

A

First 1/3 is skeletal, middle transitions to smooth and the lower part is smooth.

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21
Q

What are the 4 structures that cause the three constrictions of the esophagus?

A
  1. cricopharyngeus muscle
  2. aortic arch crossing its anterior surface
  3. left primary bronchus below the arch of the aorta
  4. diaphragm, as the esophagus passes into the abdomen
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22
Q

When are the constrictions seen?

A

Only when swallowing a barium meal.

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23
Q

Why are the constrictions of the esophagus important?

A

Foreign objects are more likely to lodge there, perforation are possible and carcinomas are more common.

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24
Q

What is the innervation to the esophagus?

A

esophageal plexus of nerves

25
Q

What are the components of the esophageal plexus of nerves?

A

1 .vagal fibers

  1. sympathetic fibers
  2. sensory fibers
26
Q

Describe the path of the right vagus nerve.

A

Right vagus nerve contributes fibers to the esophageal plexus, then passes posterior to esophagus, breaks up and contributes fibers to the POSTERIOR ESOPHAGEAL PLEXUS. It then reforms as the POSTERIOR VAGAL TRUNK and descends through the esophageal hiatus to the abdomen.

27
Q

What does the left vagus nerve contribute to?

A

Contributes multiple fibers to the cardiac plexus and then breaks up to form the ANTERIOR ESOPHAGEAL PLEXUS. Distally it reforms, becomes the ANTERIOR VAGAL TRUNK, which leaves the thorax through the esophageal hiatus.

28
Q

Parasympathetic innervation from the vagal fibers stimulates what processes?

A

Peristalsis and glandular secretions.

29
Q

Where do sympathetic fibers from the esophageal plexus come form?

A

Post-gang from T1-T5 and some pregang fibers from the greater splanchnic nerve

30
Q

What do the sympathetic fibers of the esophageal plexus do?

A

Inhibit peristalsis

31
Q

How do visceral afferents in the vagus and sympathetic branches vary?

A

Visceral afferents in the vagus transmit info about normal physiological process.

VA in the sympathetic carry pain information.

32
Q

How do you view the esophagus?

A

With an esophagoscope

33
Q

What do you do if a good echocardiogram can’t be obtained with a usual transthoracic procedure?

A

TEE

A transducer is introduced into the lower esophagus to get a more detailed view of the heart and great vessels without interference from the ribs or lungs.

34
Q

What supplies blood to the thoracic esophagus?

A

Branches of the abdominal aorta enter the thorax via the esophageal hiatus and supply the lower esophagus.

35
Q

What are the paths of venous drainage for the esophagus?

A
  1. Submucosal plexuses goes to the azygous and hemiazygous ystems
  2. Branches form the lower esophagus drains to the L gastric vein
36
Q

Where does lymphatic drainage of the esophagus go?

A

It returns to the posterior mediastinal and left gastric nodes. Lymph from the cervical esophagus drains to the cervical nodes.

37
Q

What is the path of the descending part of the aorta?

A

It extends from T4 to T12 and travels through the aortic hiatus behind the diaphragm at T 12.

38
Q

Where do the thoracic duct and azygos vein lie in relation to the aorta?

A

They lie to the right of the aorta and also go through the aortic hiatus.

39
Q

What are the major branches of the thoracic aorta?

A
  1. posterior intercostal arteries (supply intercostal spaces 3-11)
  2. subcostal arteries (supply 12th intercostal sapce)
  3. visceral branches (esophagus, bronchi, mediastinum, pericardium)
  4. superior phrenic (small branches to diaphragm)
40
Q

What is an aortic aneurysm?

A

Dilation of a defined area of an artery, that usually occurs in ascending or descending parts of the aorta.

41
Q

What are the symptoms of an aortic aneurysm?

A
  1. hoarseness (pressure on L. recurrent laryngeal nerve)
  2. dysphagia (difficulty swallowing from pressure on the esophagus)
  3. dyspnea (difficulty in breathing following pressure on the trachea, root of lung, or phrenic nerve)
42
Q

What is the thoracic duct?

A

Main lymphatic return to the venous system that conveys about 75% of the lymph of the body through a thin walled duct with valves.

43
Q

What does the thoracic duct do?

A

Drains the cisterna chyli, that’s located in the abdomen at T12-L1.

44
Q

What is the path of the thoracic duct?

A

Passes superiorly from the cisterna chyli through the aortic hiatus into the posterior mediastinum, and lies bewteen the azygous vein and the descending aorta.

45
Q

Where does the thoracic duct terminate?

A

At the confluence of the left internal jugular and subclavian veins.

46
Q

What does the thoracic duct receive?

A

Lymphatic vessels from the lower right intercostal spaces, the left intercostal spaces and from posterior mediastinal lymph nodes.

47
Q

What is a chylothorax?

A

A laceration of the thoracic duct that results in lymph escaping into the thoracic cavity.
**fluid can be removed by thoracentesis

48
Q

What forms the azygos vein?

A
  1. The right subcostal vein, draining the 12th intercostal space, and the
  2. R ascending lumbar vein, from the abdomen, join and from it.
49
Q

What does the azygos vein receive?

A

Posterior intercostal veins draining intercostal spaces R2-11 (venous return from the 1st space drains into the right brachiocephalic vein) and veins of the esophageal plexus.

50
Q

Where does the azygos vein ascend?

A

It ascends posterior to the mediastinum on the RIGHT side of the vertebral column.

51
Q

Where is the arch of the azygous vein formed?

A

At T4, the arch of hte azygous vein is formed over the root of the right lung where it joins the SVC

52
Q

What forms the hemiazygous vein?

A

The junction of the left subcostal and left ascending lumbar veins.

53
Q

What is different between the drainage of lower and upper intercostal veins?

A

LOWER posterior intercostal veins and esophagela veins on the left side drain into the hemiazygous vein

UPPER left posterior intercostal veins may drain into an accessory hemiazygos vein, which joints the hemiazygos vein at a variable level.

54
Q

What do the posterior intercostal veins drain?

A

The uppermost 3 or 4 intercostal spaces that then drain into the superior intercostal vein which empties into the brachiocephalic vein.

55
Q

Clinically, why is the azygos system important?

A

It forms an anastomosis between the IVC and the SVC and will form an important alternative circulation in case of obstruction of either vessel.

56
Q

Where does the sympathetic trunk run in the thoracic cavity?

A

The R and L sympathetic trunks run a vertical paravertebral course on the posterior wall of the thoracic cavity.

57
Q

What preganglionic sympathetic fibers do NOT synapse in the sympathetic trunk and instead pass forward as planchnic nerves?

A
  1. Greater planchnic nerve (fibers form spinal cord levels T5-9)
  2. Lesser splanchnic nerve (fibers from T10-T11 spinal cord levels)
  3. Least splanchnic nerve (fibers form T 12)
58
Q

Where do the splanchnic nerves travel to?

A

These PRE-GANG SYMPATHETIC FIBERS (MYELINATED) TRAVEL TO THE ABDOMEN, HWERE THEY SYNAPSE IN PREVERTEBRAL GANGLIA

(some sympatehtic pre-gang ascend and synapse on cervical ganglia and supply structures in the head and neck)

CRAAB 3 (7 decks)

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