**Question:** Sequestered lobe of lung is commonly supplied by-

A. Pulmonary artery
B. Aorta
C. Azygos system
D. Other bronchus

**Core Concept:** Sequestered lung lobes are anatomical variations in which a portion of a lung remains undeveloped, resulting in a separate and hypoplastic lobe receiving its blood supply from an alternative source. The normal pulmonary arteries supply the majority of the lung tissue. However, in cases of sequestered lobes, the blood supply might be from an atypical source, such as the azygos system or a bronchus.

**Why the Correct Answer is Right:** The correct answer, **A. Pulmonary artery**, represents the normal scenario where the majority of lung tissue receives blood supply from pulmonary arteries. However, in cases of sequestered lobes, this principle is deviated.

**Why Each Wrong Option is Incorrect:**

**A. Aorta:** In most cases, the sequestered lobe will receive blood from the pulmonary artery, which is connected to the aorta. Selecting the aorta as a blood supply source is incorrect because it is the primary vessel supplying systemic circulation and not specifically supplying lung tissue.

**B. Azygos system:** The azygos system is a collateral circulation system that arises from the thoracic aorta and supplies deoxygenated blood to the chest, but it does not directly supply a lung lobe. This option is incorrect because it is not the primary source for a sequestered lung lobe's blood supply.

**C. Other bronchus:** A bronchus could potentially supply a sequestered lobe if the primary pulmonary artery is not available, but bronchioles typically do not carry enough blood volume to supply a whole lung lobe. This option is incorrect because it is not a reliable primary source for a sequestered lung lobe's blood supply.

**Clinical Pearl:** Sequestered lung lobes are commonly found in children and can present with recurrent respiratory infections due to the abnormal vascular supply. Recognizing these variations is crucial for accurate diagnosis and management.

In summary, the correct answer (A. Pulmonary artery) reflects the normal lung lobe's blood supply, while the wrong options (Azygos system, Other bronchus) do not represent the primary blood supply source for sequestered lung lobes.