AN23.1-6 | Mediastinum — Gate Quiz — AN23.1-6

Q1 1 pt

A Xiphoid process

B Sternal angle (angle of Louis) ✓

C Manubriosternal notch

D Carina of the trachea

Correct. The sternal angle (T4/T5 level) is the key horizontal plane dividing the mediastinum.

The sternal angle — where the manubrium meets the body of sternum — marks the T4/T5 plane dividing the mediastinum.

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Q2 1 pt

A Oesophagus

B Heart and pericardium

C Thymus remnant and internal thoracic vessels ✓

D Thoracic duct

Correct. The anterior mediastinum (between sternum and pericardium) contains the thymus/fat, internal thoracic vessels, and lymph nodes.

The anterior mediastinum contains the thymus, internal thoracic vessels, and lymph nodes — not the heart (middle) or thoracic duct (posterior).

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Q3 1 pt

A Left main bronchus — it is wider and more vertical

B Right main bronchus — it is wider, shorter, and more vertical ✓

C Left main bronchus — it is longer

D Right main bronchus — it has a more acute angle

Correct. The right main bronchus is wider, shorter, and more vertical, making it the preferential path for aspirated foreign bodies.

The right main bronchus — being wider, shorter, and more vertical — preferentially receives aspirated foreign bodies.

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Q4 1 pt

A Caval opening (T8)

B Oesophageal hiatus (T10)

C Aortic hiatus (T12) ✓

D It pierces the muscular diaphragm separately

Correct. The thoracic duct enters the thorax through the aortic hiatus at T12, lying between the aorta and azygos vein.

The thoracic duct passes through the aortic hiatus at T12 (alongside the aorta and azygos vein).

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Q5 1 pt

A Below T5, on the right side of the vertebral column

B Above T5, after the duct has crossed to the left ✓

C At the cisterna chyli (L1–L2)

D At the aortic hiatus (T12)

Correct. The duct crosses from right to left at T5. Injury above T5 (left-sided duct) causes left chylothorax; injury below T5 (right-sided duct) causes right chylothorax.

The thoracic duct crosses to the left at T5. Left-sided chylothorax results from injury above T5 where the duct is on the left.

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Q6 1 pt

A Right vagus nerve near the trachea

B Left recurrent laryngeal nerve under the aortic arch ✓

C Right phrenic nerve near the hilum

D Left phrenic nerve near the cardiac apex

Correct. The left recurrent laryngeal nerve loops under the aortic arch and is vulnerable to compression by left hilar or mediastinal malignancy.

The left recurrent laryngeal nerve is uniquely vulnerable at the aortic arch. Its proximity to the left hilum makes it susceptible to lung cancer, aortic aneurysm, and lymphoma.

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Q7 1 pt

A T8 — with the inferior vena cava

B T10 — with the two vagal trunks ✓

C T12 — with the aorta and thoracic duct

D T6 — with the azygos vein

Correct. The oesophagus passes through the oesophageal hiatus at T10, accompanied by the anterior and posterior vagal trunks.

The oesophageal hiatus is at T10 and transmits the oesophagus plus the two vagal trunks.

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Q8 1 pt

A Vagus nerve (CN X) — C1, C2, C3

B Phrenic nerve — C3, C4, C5 ✓

C Intercostal nerves — T6–T12

D Greater splanchnic nerve — T5–T9

Correct. The phrenic nerve (C3, C4, C5) is the sole motor supply to the diaphragm. "C3, 4, 5 keeps the diaphragm alive."

The phrenic nerve (C3, C4, C5) is the motor nerve to the diaphragm. Mnemonic: "C3, 4, 5 keeps the diaphragm alive."

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Q9 1 pt

A Left gastric vein (portal) and oesophageal tributaries of azygos (systemic) ✓

B Superior mesenteric vein (portal) and inferior vena cava (systemic)

C Splenic vein (portal) and left renal vein (systemic)

D Inferior mesenteric vein (portal) and internal iliac vein (systemic)

Correct. Oesophageal varices arise from the porto-systemic anastomosis between the left gastric vein (portal) and oesophageal tributaries of the azygos system (systemic).

Oesophageal varices = left gastric vein (portal) ↔ oesophageal branches of azygos vein (systemic). This is the critical porto-systemic anastomosis in the posterior mediastinum.

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Q10 1 pt

A Trachea → Oesophagus → Aortic arch → Brachiocephalic veins

B Thymus → Brachiocephalic veins → Aortic arch → Trachea → Oesophagus ✓

C Aortic arch → Thymus → Trachea → Brachiocephalic veins → Oesophagus

D Brachiocephalic veins → Trachea → Aortic arch → Thymus → Oesophagus

Correct. Anterior to posterior: Thymus → Brachiocephalic veins → Aortic arch → Trachea → Oesophagus.

The correct order is: Thymus → Brachiocephalic veins → Aortic arch → Trachea → Oesophagus (anterior to posterior).

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