Thoracic Cavity: Mediastinum

Question 1

Boundaries of mediastinum

Answer 1

• Superior thoracic aperture (superior)
• Diaphragm (inferior)
• Sternum (anterior)
• Thoracic vertebrae (posterior)
• Mediastinal pleura (lateral)

Question 2

Divisions of mediastinum

Answer 2

• Superior mediastinum
• Anterior mediastinum
• Middle mediastinum
• Posterior mediastinum

Question 3

Boundaries and contents of superior mediastinum

Answer 3

PVT Left BATTLE
- Phrenic nerve
- Vagus nerve
- Thoracic duct
- Left recurrent laryngeal nerve
- Brachiocephalic veins, SVC
- Arch of aorta (with branches)
- Thymus
- Trachea
- Lymph nodes
- Esophagus

Question 4

Boundaries and contents of anterior mediastinum

Answer 4

• Internal thoracic vessels
• Sterno-pericardial ligaments
• Loose areolar tissue
• (Thymus in children)

Question 5

Boundaries and contents of posterior mediastinum

Answer 5

DATES
- Descending aorta (with branches)
- Azygous system of veins
- Thoracic duct
- Esophagus with vagus nerves
- Sympathetic trunk and thoracic splanchnic nerves

Question 6

Boundaries and contents of middle mediastinum

Answer 6

• Heart with pericardium
• Roots of great vessels:
  >Ascending aorta
  >Pulmonary trunk
  >SVC
  >IVC
  >Pulmonary veins

Question 7

Types of pericardium

Answer 7

• Outer fibrous pericardium
• Serous pericardium

Question 8

Connections of fibrous pericardium

Answer 8

• Apex fused with outer connective tissue layer of great blood vessels
• Base fused with central tendon of diaphragm
• Anteriorly attached to sterno-pericardial ligaments

Question 9

Layers of serous pericardium

Answer 9

• Parietal layer (outer, close to fibrous)
• Visceral layer (inner, close to heart)

Question 10

What is the space between the parietal and visceral layers called?

Answer 10

Pericardial cavity

Question 11

What does the pericardial cavity allow and how?

Answer 11

Friction free expansion as it contains a thin film of fluid

Question 12

What is pericarditis?

Answer 12

Inflammation of the serous pericardium

Question 13

What is cardiac tamponade?

Answer 13

Compression of the heart when the pericardial cavity fills with excess fluid

Question 14

Surfaces of the heart

Answer 14

• Anterior surface = RA, RV and LV, LA
• Posterior surface (AKA base) = Mainly LA (some RA)
• Inferior surface = RV and LV

Question 15

Borders of the heart

Answer 15

• Right border = RA, from SVC to IVC
• Left border = Left auricle and LV
• Apex = LV (in left 5th ICS, 1-2cm medial to midclavicular line)

Question 16

How is cardiothoracic ratio calculated?

Answer 16

CTR = A/B
A = transverse heart dimension
B = maximum dimension of chest

Question 17

What is cardiomegaly and what CTR value determines it?

Answer 17

Enlarged heart, CTR > 0.5

Question 18

Where do cardiac veins drain into?

Answer 18

Coronary sinus (then right atrium)

Question 19

What are angina and myocardial infarction and what are they caused by?

Answer 19

• Angina = chest pain
• Myocardial infarction = heart attack
• Both caused by narrowing of coronary vessels (so reduced blood supply)

Question 20

Where do lymphatics drain into in the heart?

Answer 20

Brachiocephalic and tracheobronchial nodes