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Anatomy > Mediastinum II > Flashcards

Mediastinum II Flashcards

1
Q

Describe the location of the Mediastinum.

A

It’s the middle area of the thoracic cavity, situated between the right lung and pleural cavity and left lung and pleural cavity.
It extends from the 1st rib above to the diaphragm.
And it’s the area between the sternum anteriorly and the vertebral column posteriorly.

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2
Q

What are the contents of the middle mediastinum?

A

The heart, the orgins of the great vessels, the fibrous pericardium and the serous pericardium

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3
Q

What’s the location of the superior mediastinum?

A

Above the middle mediastinum. It extends from the 1st rib above to the T4/5 plane inferiorly.

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4
Q

What is the T4/5 plane?

A

It’s a line that passes from the manubriolsternal joint anteriorly to cut the intervetebral disc between the 4th and 5th thoracic vertebrae.

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5
Q

What’s the location of the posterior mediastinum?

A

Posterior to the middle mediastinum and the diaphragm

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6
Q

What’s the location of the anterior mediastinum?

A

Anterior to the middle mediastinum, between the middle mediastinum and the sternum.

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7
Q

What are the contents of the anterior mediastinum?

A

The thymus gland, the internal thoracic or internal mammary arteries, the internal thoracic veins and the parasternal or internal thoracic chain of lymph nodes.

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8
Q

Describe the Thymus gland

A

It’s a bi-lobed organ, which extends below the T4/5 plane just behind the sternum (part of the thymus gland projects above the T4/5 plane, so it’s also part of the superior mediastinum.

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9
Q

Describe the internal thoracic arteries

A

They are branches of the subclavian arteries and they pass down the anterior chest wall and enter the anterior mediastinum to give off anterior intercostal arteries to the anterior parts of the intercostal spaces.

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10
Q

How do you find the position of the T4/5 plane on a patient?

A

You find the sternal angle, or angle of Louis.

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11
Q

Describe the features that occur on the T4/5 plane

A
  • The costal cartilages of the 2nd rib articulate with the sternum at the manubrio-sternal joint
  • The ascending aorta joins the aortic arch and the aortic arch also ends on the T4/5 plane by joining the the descending thoracic aorta
  • There’s the bifurcation of the pulmonary trunk into the right and left pulmonary arteries
  • Bifurcation of the trachea into the right and left mainstem bronchi
  • Arch of azygos vein go over the right main bronchus to enter into the superior vena cava
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12
Q

Describe the contents of the superior mediastinum

A
  • Remains of thymus gland (although atrophied)

- Venous plane, Arterial plane, Wind Plane and Water plane

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13
Q

Describe the venous plane of the superior mediastinum

A

Consists of the two brachiocephalic veins

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14
Q

Describe how the brachiocephalic veins are formed

A

The right brachiocephalic - Union of the right subclavian vein with the right internal jugular vein
The left brachiocephalic - Union of the left internal jugular vein and the left subclavian vein.

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15
Q

How the right and left brachiocephalic veins come together?

A

They come together at the level of the sternoclavicular joint. The left brachiocephalic has to angle across, behind the manubrium of the sternum and join the right brachiocephalic vein and empty into the superior vena cava.

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16
Q

What are the contents of the arterial plane of the superior mediastinum?

A

The aortic arch and its branches

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17
Q

What are the 3 principal branches arising from the aorta?

A
  • The brachiocephalic artery
  • The left common carotid artery
  • The left subclavian artery
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18
Q

Describe the Brachiocephalic Artery

A

It ascends to the level of the sternoclavicular joint, where it divides into the right subclavian artery (taking blood to the right upper limb) and the right common carotid artery (supplying blood to the head and neck.

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19
Q

What’s the function of the left common carotid artery?

A

It supplies blood to the left side of head and neck

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20
Q

What’s the function of the left subclavian artery?

A

It supplies blood to the left upper limb

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21
Q

Is there an asymetry in arterial distribution on the arch of the aorta?

A

Yes, there’s no left brachiocephalic artery. There are two separate arteries: left common carotid and the left subclavian artery.

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22
Q

What are the contents of the wind plane in the superior mediastinum?

A

The trachea

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23
Q

Where does the trachea begin?

A

Where it connects with the larynx (level of 6th cervical vertebra)

24
Q

What are the contents of the water plane in the superior mediastinum?

A

The esophagus

25
Q

Where does the esophagus begin?

A

Where it joins with the laryngopharynx (level of 6th cervical vertebra)

26
Q

Why does the trachea needs to have a soft posterior wall?

A

To allow the esophagus to distend into it.

27
Q

Which nerves pass through the superior mediastinum?

A

The phrenic nerves and the vagus nerves

28
Q

Where do the branches of the phrenic nerves come from?

A

They come from the anterior primary rami of the 3rd, 4th and 5th cervical spinal nerves.

29
Q

Explain the pathway of the phrenic nerves until their destination

A

The branches leave the anterior primary rami of the 3rd, 4th and 5th cervical nerves. These branches come together in the neck to form the phrenic nerves . And they descend through the neck, the subclavian artery and vein, the superior vena cava, the heart on their way down to innervate the diaphragm.

30
Q

How many vagus nerves there are?

A

2 (and they are the 10th cranial nerve)

31
Q

Describe the pathway of the right vagus nerve all the way to the esophageal plexus.

A

Brainstem - descend through the neck (alongside carotid arteries) and enter the superior mediastinum. Then crosses the subclavian artery - passes behind the root of right lung and will finally join the network of nerves called esophageal plexus.

32
Q

THE RIGHT RECURRENT LARYNGEAL NERVE IS NOT A CONTENT OF THE SUPERIOR MEDIASTINUM (True or False)

A

True. It recurs around the subclavian artery, which already left the superior mediastinum.

33
Q

What’s the function of the right recurrent larygenal nerve?

A
  • It innervates the muscles that operate the vocal cord on the right side of the larynx.
  • It also supplies sensory fibers to the mucous membrane that lies below the vocal cord on the right side.
34
Q

Describe the pathway of the left vagus nerve all the way to the esophageal plexus.

A

Brainstem - descend long carotid artery - cross arch of the aorta, passes through the root of left lung ad join the esophageal plexus.

35
Q

Where does the left vagus nerve gives off the left recurrent laryngeal nerve?

A

As it crosses the arch of the aorta. It loops under the arch of the aorta, right at ligamentum arteriosum.
Then it ascends back up into the neck and it innervates the muscles that move the vocal cord on the left side. And provides sensory fibers to the mucous membrane below the left vocal cord.

36
Q

Why patologies that occuer in the superior mediastinum will affect the voice?

A

Because it could cause interference with the function of theleft recurrent nerve.

37
Q

Where does the esophagus penetrates the diaphragm?

A

At the esophageal hiatus ( at T10 level)

38
Q

Describe the esophagus location

A

It is more or less a midline structure lying anterior to the vertebral column,although it moves slightly anteriorly as it approaches the diaphragm

39
Q

In which two places can food become lodged in the esophagus?

A

1- Where the esophagus is crossed by the left mainstem bronchus - in the location of the arch of the aorta ( the left bronchus in front of it, the aortic arch to the left and the vertebral column behind.
2- Where it passes through the diaphragm (level of 10th thoracic vertebra) - the esophageal hiatus because it’s surrounded by the fibers of the diaphragm.

40
Q

What are the contents of the posterior mediastinum?

A
  • The esophagus
  • The descending thoracic aorta
  • Azygos and Hemiazygos veins
  • Thoracic duct
41
Q

Where does the descending thoracic aorta penetrates the diaphragm?

A

At the aortic hiatus ( level of 12th thoracic vertebra)

42
Q

What arteries does the descending thoracic aorta gives off when it descends through the posterior mediastinum?

A

The posterior intercostal arteries(to the intercostal spaces ad well as branches to the esophagus - the esophageal arteries).
The aorta also supplies bronchial vessels to the airways entering the lung on the left side ( sometimes on the right side , but he right main bronchus typically gets its blood supply from branches of adjacent intercostal arteries.)

43
Q

What is the function of the azygos and hemiazygos veins?

A

The blood that is distributed to tissues by the posterior intercostal arteries will be received or drained by the azygos and hemiazygos veins.

44
Q

Describe the drainage process in the hemiazygos veins.

A

Hemiazygos - They have a connection with ascending lumbar veins in the abdomen , as they approach diaphragm, they drain into the hemiazygos vein which also receives (on the left hand side) the contents of the posterior intercostal veins from the lower intercostal spaces.

45
Q

Describe the drainage process in the accessory hemiazygos veins.

A

The accessory hemiazygos vein lies on the left-hand side of the posterior mediastinum and is receiving blood from the posterior intercostal veins in the upper intercostal spaces

46
Q

Where both the hemiazygos and the accessory hemiazygos vein drain?

A

They cross the midline to drain into the azygos vein.

47
Q

Describe the draining process of the azygos vein.

A

The azygos vein itself is on the right side of the posterior mediastinum and is collecting blood from the posterior intercostal veins on the right-hand side. It ascends to empty into the superior vena cava by arching over the root of the right lung and emptying into the superior vena cava at that point.

48
Q

What is the thoracic duct?

A

The thoracic duct is located in the posterior mediastinum and is the largest of the lymphatic channels in the body.

49
Q

Where is the cisterna chyli?

A

It is situated in the aortic hiatus of the diaphragm. So, it’s just in between the aorta and the vertebral column.

50
Q

What is the function of the cisterna chyli?

A

It’s a sack like structure that receives all of the lymph that is coming up from the legs and from the abdomen

51
Q

Describe the pathway of lymph from the cisterna chyli to the venous system

A

Cisterna chyly receives lymph from legs and abdomen, drains into thoracic duct that will ascend all the way up to the usperior mediastinum and empty it in one of the veins near the point of union of the left internal jugular and left subclavian.
The point of return of the lymph varies. Sometimes the the left internal jugular vein, sometimes the left subclavian vein. Sometimes the left brachiocephalic vein.

52
Q

What are the sympathetic chains?

A

They are two strands of nerve ganglia, connected to one to the other by bundles of nerve fibers, that lie on either side of the vertebral column

53
Q

What’s the other name of the sympathetic chains?

A

paravertebral ganglia.

54
Q

Are the sympathetic chains restricted to the posterior mediastinum?

A

No, In fact, the sympathetic chains extend from the neck - they begin at the base of the skull,extend through the cervical part of the vertebral column, then they go through the superior mediastinum , then they go through the posterior mediastinum and they extend down into the abdomen and into the pelvis.

55
Q

To what nervous system the sympathetic chains belong?

A

Autonomic Nervous System

Anatomy (2 decks)

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