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Y2S1 ANATOMY > Anatomy of mediastinum > Flashcards

Anatomy of mediastinum Flashcards

1
Q

What is the mediastinum?

A

It is a space of partition between the two pleural cavities that extends from the sternum anteriorly to the vertebral column posteriorly and from the thoracic inlet above to the diaphragm below

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2
Q

What are the divisions of the mediastinum?

A

1) Superior mediastinum

  • Above an imaginary line between the angle of lewis till the posterior aspect of the fourth vertebrae

2) Inferior mediastinum

  • Below the imaginary plane and it is divided into:

1) Anterior mediastinum

  • Behind the body and xiphoid process

2) Middle mediastinum

  • Occupied by the pericardium and the heart

3) posterior mediastinum

  • Behind the middle mediastinum
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3
Q

What are the boundaries of the superior mediastinum?

A

1) Superiorly:

Thoracic inlet

2) Inferiorly

  • Imaginary line extending from the sternal angle to the inferior portion of the fourth vertebrae

3) Anteriorly

  • Manubrium of the sterni

4) Posteriorly

  • Upper four thoracic vertebrae

5) On each side

  • Mediastinal pleura
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4
Q

What are the contents of the superior mediastinum?

A

1) Muscles

2) Viscera

3) Arteries

4) Veins

5) Nerve

6) Thymus gland

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5
Q

What is the muscle content of the superior mediastinum?

A

1) Sternohyoid (attached sternum)

2) Sternothyroid anteriorly (attached to the sternum)

3) Longus coli posteriorly

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6
Q

What is the viscera content of the superior mediastinum?

A

1) Esophagus

  • It is the most posterior structure lying behind the trachea and in front of the vertebrae

2) Trachea

  • Lies in the midline in front of the esophagus
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7
Q

What is the arterial content of the superior mediastinum?

A
  • It lies in front of the trachea

1) Arch of the aorta

  • behind the lower half of the manubrium sterni

2) Branches of the aorta

    1. brachiocephalic, 2. left common carotid and 3. left subclavian arteries, Behind the upper part of the manubrium sterni
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8
Q

What is the vein content of the superior mediastinum?

A

1) Right brachiocephalic vein

  • Descends on the right side of the brachiocephalic artery

2) Left brachiocephalic vein (innominate vein)

  • Passes obliquely in front of the aortic arch branches, uniting with the right brachiocephalic vein at the level of the first right intercostal/ cartilage forming the SVC

3) Superior vena cava

  • Formed by the union of the left and right brachiocephalic veins the azygous vein opens into it at the level of the 2nd costal cartilage, and it opens into the RA at the level of the 3rd costal cartilage

4) Left superior intercostal cein

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9
Q

What is the nerve content of the superior mediastinum?

A

1) Right Vagus

  • Runs on the side of the trachea

2) Left vagus

  • Left to the left subclavian artery, descend to the left side of the aortic arch
  • The vagus will be seen in the superior and posterior inferior mediastinum

3) Right phrenic nerve

  • Descends on the right side of the right brachiocephalic vein

4) left phrenic nerve

  • Left to the common carotid and aortic arch
  • The phrenic nerve will be seen in the superior and middle inferior mediastinum

5) Left recurrent laryngeal nerve

  • Arises from the left vagus, curving below the arch of the aorta and ascending between the trachea and esophagus

6) Cardiac branches

  • From the two vagus nerves
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10
Q

What is the gland content of the superior mediastinum?

A
  • The thymus gland, is on the inner surface of the manubrium.
  • In front of all the contents mentioned above we will see the thymus gland which occupies the superior and the anterior of the inferior mediastinum
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11
Q

What is the lymph content of the superior mediastinum?

A

1) Thoracic duct

  • Left side of the esophagus (most posterior)
  • Enter the thorax through the opening of the aorta at the level of T12, initially ascending at the right side of the esophagus till the level of the sternal angle where it crosses to the left side
  • At the posterior mediastinum is at the right side of the esophagus

2) Groups of lymph nodes

  • Brachiocephalic
  • Paratracheal
  • Superior tracheobronchial
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12
Q

From which nerve does the left recurrent laryngeal nerve arises?

A

The left vagus nerve

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13
Q

What is the site of the anterior mediastinum?

A

Below the level of the sternal angle in the front part of the mediastinum

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14
Q

What are the boundaries of the anterior mediastinum?

A

1) Anteriorly:

  • The body of the sternum

2) Posteriorly

  • The pericardium

3) Lined by the plural on each side

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15
Q

What are the contents of the anterior mediastinum?

A

1) Superior and inferior sternopericardial ligaments

2) Parts of the remnants of the thymus gland

3) Internal mammary artery

4) 2/3 lymph nodes and lymphatics

5) Areolar tissue

6) Sternocostalis muscle

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16
Q

What is the site of the middle mediastinum?

A

The part of the mediastinum that is occupied by the pericardium and its contents

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17
Q

What are the boundaries of the middle mediastinum?

A

1) Superiorly

  • The imaginary horizontal line

2) Inferiorly

  • The diaphragm

3) Anteriorly

  • The anterior mediastinum

4) Posteriorly

  • The posterior mediastinum
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18
Q

What are the contents of the middle mediastinum?

A

1) The pericardium and the heart

2) The ascending aorta

3) The pulmonary trunk

4) The bifurcation of the pulmonary trunk into right and left pulmonary arteries

5) The lower half of the SVC

6) The upper-most part of the inferior vena cava

7) The four pulmonary veins

8) The bifurcation of the trachea

9) The right and left phrenic nerves along the side of the pericardium

10) The inferior tracheobronchial lymph nodes (below the bifurcation of the trachea

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19
Q

What is the site of the posterior mediastinum?

A

Between the pericardium and the vertebral column

20
Q

What are the boundaries of the posterior mediastinum?

A

1) Superiorly

  • The horizontal imaginary line

2) Inferiorly

  • The diaphragm

3) Anteriorly

  • The pericardium above and the diaphragm below

4) Posteriorly

  • The lower 8 thoracic vertebrae
    from T5-T12

5) The mediastinal pleura on both sides

21
Q

What are the contents of the posterior mediastinum?

A

1) Descending aorta

2) Esophagus on the right side of the aorta, which crosses to the left on the lower part of the aorta

3) Azygos (right side) and hemiazygos veins (left side)

4) The two vagus nerves that form the esophageal plexus

5) Splanchnic nerves, which arise from the sympathetic trunk

6) The thoracic duct, ascends on the right side of the esophagus

7) Posterior mediastinal lymph nodes

22
Q

What is the origin of the ascending aorta?

A

Located in the middle of the inferior mediastinum, it originates from the orifice of the left ventricle, behind the left margin of the sternum at the level of the left 3rd intercostal space

23
Q

What is the course and termination of the ascending aorta?

A

1) It ascends upwards, forwards, and to the right

2) It terminates behind the right margin of the sternum at the level of the right 2nd costal cartilage turning into the arch of the aorta

24
Q

What are the branches of the ascending aorta?

A
  • It has three dilatations (aortic sinuses)

1) Right coronary artery (from the anterior aortic sinus)

2) Left coronary artery (from the left posterior aortic sinus)

25
Q

Where does the aortic arch begin?

A

At the right 2nd costal cartilage, as a continuation of the ascending aorta

26
Q

What is the level of termination of the aortic arch and its course?

A

1) It terminates at the border of the 4th thoracic vertebrae by becoming the descending aorta

2) It passes upwards, backward, and left to the trachea, then curves to the left side of the trachea, then curves downwards on the left side of the lower border of T4

  • If you realize that it begins and terminates at the level of the fourth vertebrae
27
Q

What are the branches of the aortic arch?

A

1) Brachicephalic artery

2) Left common carotid artery

3) Left subclavian artery (behind the left common carotid)

28
Q

What is the most common location and type of aneurysm of the aorta?

A

Given the different types of aneurysms, the distal part of the ascending aorta is not reinforced by the fibrous pericardium which makes it susceptible to aneurysm due to the strong thrust of blood when the left ventricles contract, and due to its location, it can exert pressure on the trachea and esophagus making it difficult to breath and swallow

29
Q

What forms the superior vena cava?

A

The union of the right and left brachiocephalic veins at the level of the 1st right costal cartilage

30
Q

At what level does the superior vena cava terminate?

A

It ends at the level of the 3rd costal cartilage, opening into the right atrium

31
Q

What are the tributaries of the superior vena cava?

A

1) Azygous vein

  • At the level of the second costal cartilage, before the SVC pierces the pericardium

2) Several small veins

32
Q

Describe the structure of the trachea and bronchi

A
  • The trachea consists of hyaline cartilage, muscle, connective tissue, mucous membrane, and glands
  • The hyaline cartilage is 16-20 rings, and incomplete posteriorly to allow us to swallow but is separated from the esophagus by the muscles and connective tissues
  • Regarding the bronchi, the right bronchi is shorter, wider, and more vertical, it enters the hilum at the level of the 5th thoracic vertebrae, where compared to the right one which enters the hilum at the level of the 6th thoracic vertebrae
33
Q

At what level does the trachea begin and terminate?

A

1) It begins at the lower border of the 6th cervical vertebrae, where it is continuous with the larynx, at this level the pharynx turns into the esophagus

2) It terminates at the level of the upper border of the 5th thoracic vertebrae

34
Q

Describe the course of the trachea

A
  • The upper half is in the neck, while the lower half is in the thorax
  • the lower part only deviates to the right but mainly it is in the median plane
35
Q

Describe the course of the left vagus nerve in the superior mediastinum

A

1) It enters the thorax between the left common carotid and the left subclavian arteries

2) It crosses the left side of the aortic arch giving the left recurrent laryngeal nerve

3) It continuous downward posterior to the root of the left lung

36
Q

Describe the course of the recurrent laryngeal nerve

A

1) It winds around the arch of the aorta

2) It ascends between the trachea and esophagus

37
Q

Describe the course of the right vagus in the superior mediastinum

A

Crosses in front of the right subclavian artery giving the right recurrent laryngeal nerve

38
Q

What is the importance of the sternal angle?

A

1) The second costal cartilage and rib lies at this level

2) The ascending aorta ends at this level

3) The arch of the aorta begins at this level

4) Descending aorta begins at this level

5) At this level the trachea bifurcates into two bronchi

6) The pulmonary trunk bifurcates into two pulmonary arteries, right and left

7) The azygos vein opens into the SVC

8) The thoracic duct crosses the esophagus to reach to the left side

39
Q

What conditions can affect the left recurrent laryngeal nerve?

A

1) Bronchogenic or esophageal carcinoma

2) Enlargement of the mediastinal lymph nodes

3) Aneurysm of the arch of the aorta

  • Anything that affects it will cause hoarseness of the sound as it supplies the larynx
40
Q

where does the esophagus begin and terminate?

A

1) It begins at the lower border of C6 where it is continuous with the pharynx

2) It terminates as it exits the diaphragm at the level of T10 and ends in the stomach at T11

41
Q

Describe the course of the esophagus

A
  • At its origin, it lies in the median plane

1) Descends vertically downwards through the superior and posterior mediastinum but with two curvature towards the left

1) The first curvature occurs through the root of the neck, then it reaches the midline again at the level of the 5th thoracic vertebra

2) Then the second curvature occurs shifting it towards the left as it moves anteriorly towards the esophageal opening in the diaphragm

  • The esophagus also has an anteroposterior flexure due to the vertebral column
42
Q

How many constrictions of the esophagus are there and at what location are they?

A
  • There are four constriction

1) At the beginning of the esophagus (6th inches from the incisor teeth)

2) Opposite to the arch of the aorta (9 inches from the incisor)

3) Opposite to the crossing of the left principle bronchus (12 inches from the incisors)

4) At the esophageal opening of the diaphragm (15 inches from the incisors)

  • These are important for gastroscope, considered as landmarks
43
Q

What is the thoracic duct?

A

It is the duct that drains all the lymph nodes except the the upper right side

44
Q

What forms the thoracic duct?

A

The union of the right jugular, right subclavian and right bronchomediastinal lymph trunks

45
Q

What portion of the body gets drained by the thoracic duct?

A

It drains all of the body except:

1) Right side of the head and neck

2) Right upper limb

3) Right lung and thoracic wall

4) Right side of the heart

5) The superior surface of the liver

46
Q

What is the origin and termination of the thoracic duct?

A

1) It originates from the cephalic end of the cisterna chyli in the abdomen (receives lymph from the lower body), entering the thorax through the aortic opening at T12

2) It terminates at the junction of the left subclavian and internal jugular veins (basically in the brachiocephalic vein)

47
Q

Describe the course of the thoracic duct

A

1) Passes through the aortic opening of the diaphragm

2) Ascends in the posterior mediastinum on the vertebral bodies right to the esophagus

3) At the level of the 5th thoracic vertebra it crosses to the left side of the esophagus in the superior mediastinum passing behind the aortic arch and subclavian artery

4) at the neck it arches above the clavicle crossing anterior to the subclavian artery and into the cephalic vein

Y2S1 ANATOMY (15 decks)

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