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Y1 - Anatomy of the Thorax > Lecture 4 - Superior mediastinum > Flashcards

Lecture 4 - Superior mediastinum Flashcards

1
Q

What are the boundaries of the mediastinum?

A

Thick midline partition separating two pleural cavities.

  • From superior thoracic inlet to inferior thoracic inlet
  • From sternum to thoracic vertebrae
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2
Q

What are the contents of the mediastinum?

A
  • Trachea
  • Oesophagus
  • Heart and pericardium
  • Thoracic duct
  • Nerves
  • Great vessels
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3
Q

What marks the border between the inferior and superior mediastinum?

A

Sternal angle

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4
Q

What are the contents of the superior mediastinum?

A
  • Thymus
  • Phrenic nerves
  • Great veins (SVC and IVC)
  • Main lymphatic trunks
  • Vagus nerves
  • Great arteries (AA, aortic arch and DA)
  • Trachea and main bronchi
  • Upper oesophagus
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5
Q

What veins form the brachiocephalic veins?

A

Internal jugular vein and the subclavian vein

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6
Q

What veins form the superior vena cava and what is their path?

A

Left and right brachiocephalic veins

- Left brachiocephalic vein crosses posterior to the manubrium to join with right brachiocephalic vein

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7
Q

What does the azygos vein drain?

A

Posterior thoracic and abdominal walls

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8
Q

Where does the azygos vein drain into?

A

Superior vena cava

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9
Q

What is the location of the pulmonary trunk in relation to the aortic arch and what is it?

A
  • Arises from the right ventricle, splitting into right and left pulmonary arteries towards the lungs, carrying deoxygenated blood.
  • Posterior to the aortic arch
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10
Q

What are the two remnants of the foetal blood circulation in the heart?

A

Ligamentum arteriosum and foramen ovale.

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11
Q

What did the ligament arteriosum do during foetal development?

A

A remnant of the ductus arteriosus, which allowed blood to flow directly from the aorta to the pulmonary trunk via a small hole in the underside of the aorta, passing posteriorly to PT.

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12
Q

What did the foramen ovale do during foetal development?

A

Acted as a shunt for blood to flow directly from the right atrium to the left atrium, preventing blood from entering the lungs which are bypassed whilst in the womb.

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13
Q

Where do the phrenic nerves originate from?

A

C3-5

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14
Q

What are the functions of the phrenic nerves?

A 
Motor to:
- Diaphragm
Sensory to:
- Central tendon of diaphragm
- Mediastinal pleura
- Pericardium
- Peritoneum of central diaphragm
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15
Q

Describe the path of the phrenic nerves?

A

Left - descends anteriorly to the lung root and crosses aortic arch alongside vagus nerves, piercing diaphragm and innervating the central region
Right - enters the mediastinum, continuing inferiorly along the right side of the SVC/IVC until it pierces the diaphragm

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16
Q

Where do the vagus nerves originate from?

A

10th cranial nerve so originates from the medulla in the brain.

17
Q

Describe the path of the vagus nerves?

A

Left - crosses posteriorly to the lung root and gives of the left recurrent laryngeal nerve
Right - lies on the trachea and crosses posterior to the lung root

18
Q

What is the function of the left recurrent laryngeal nerve?

A

Recurs around the right subclavian vein and innervates the skeletal muscles in the larynx.

19
Q

What are the boundaries of the anterior mediastinum?

A
  • Posterior to the sternum but anterior to the pericardial sac.
  • From sternal angle to the diaphragm
20
Q

What are the contents of the anterior mediastinum?

A
  • Inferior extension of thymus gland
  • Fat
  • Connective tissue
  • Lymph nodes
  • Mediastinal branches of internal thoracic vessels and sternopericardial ligaments
21
Q

What are the contents of the middle mediastinum?

A

Heart, pericardial sac, great vessels and nerves.

22
Q

What are the contents of the posterior mediastinum?

A
  • Oesophagus
  • Thoracic duct
  • Azygos vein system
  • Thoracic sympathetic trunk
  • Descending aorta
  • Posterior mediastinal lymph nodes
  • Splanchnic nerves
23
Q

What are the four regions of the mediastinum?

A

Anterior, posterior, inferior and superior.

24
Q

At what level does the phrenic nerve pierce the diaphragm?

A

Passes through at the same level as the inferior vena cava at T8.

25
Q

At what level does the oesophagus begin?

A

C7 (ends at T11)

26
Q

Describe the path of the oesophagus?

A
  • Begins at C7
  • Enters superior thoracic inlet
  • Posterior/superior mediastinum
  • T7 it deviates to the left and inclines anteriorly to pass in front of descending thoracic aorta
  • Pierces diaphragm at T10
  • Ends at stomach at T11
27
Q

Where are the four constrictions of the oesophagus?

A
  • Junction between pharynx and oesophagus
  • Where oesophagus is crossed by the aortic arch (T4/5)
  • Where oesophagus is compressed by left main bronchus
  • At oesophageal hiatus (diaphragm opening)
28
Q

What forms the brachiocephalic vein?

A

Internal jugular and subclavian veins.

29
Q

What is the general rule about positioning of arteries and veins?

A

Veins are anterior to arteries.

30
Q

What is the general rule for the positioning of the phrenic and vagal nerves?

A

Phrenic - anterior to lung root

Vagal - posterior to lung root

31
Q

Which recurrent laryngeal nerve is longer than the other?

A

The left recurrent laryngeal nerve is longer as the right is higher than the left.

32
Q

Where do the sympathetic trunks receive branches from and what do they do?

A

Spinal nerves T1-L2. Distribute sympathetic nerves to smooth muscle and glands throughout the body and bring pain fibre back to the CNS from viscera.

33
Q

Where do the splanchnic nerves arise from?

A

T5-T12 (reach the abdomen in bundles).

34
Q

Why is an AP xray used?

A

Mainly for supine patients.

35
Q

What changes in AP and PA X-rays?

A

AP - heart magnified, scapula overlaps, clavicles projected above the apex
PA - heart close to the film and undistorted, scapula rotated away from lung and clavicles cross the lung fields.

36
Q

What should the cardiothoracic ratio be?

A

Less than 0.5 - the heart should not exceed 50% of the diameter of the thorax.

Y1 - Anatomy of the Thorax (9 decks)

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