At the lung hilum, the arrangement of structures from anterior to posterior on the right side is classically remembered by which mnemonic?

Explanation

## Hilum of the Lung: Anteroposterior Arrangement (Right Side) **Key Point:** The lung hilum is the medial surface where the bronchus, pulmonary artery, and pulmonary veins enter and exit. The **anterior-to-posterior** arrangement of these structures is clinically important for surgical approaches and imaging interpretation. ### Anteroposterior Arrangement at the Right Hilum When viewing the right lung hilum from the medial aspect, the structures are arranged in the following **anterior-to-posterior** sequence: | Structure | Position | Details | | --- | --- | --- | | **Pulmonary Vein** | Anterior (most anterior) | Lies most superficially; first encountered during anterior dissection | | **Artery** | Middle (intermediate) | Pulmonary artery; lies between vein and bronchus | | **Bronchus** | Posterior (most posterior) | Largest and most rigid; lies deepest | **High-Yield:** The mnemonic **PAB** (Pulmonary vein, Artery, Bronchus) represents the **anterior-to-posterior** arrangement at the right lung hilum. This is the standard teaching in Gray's Anatomy and BD Chaurasia's Human Anatomy. **Mnemonic:** **PAB** = **P**ulmonary vein (anterior), **A**rtery (middle), **B**ronchus (posterior). ### Why the Original Answer (BAP) Is Incorrect "BAP" describes the sequence from **posterior to anterior** (deep to superficial), i.e., Bronchus → Artery → Pulmonary vein. The question stem explicitly asks for the **anterior-to-posterior** arrangement, which reverses this to **PAB**. Confusing the direction of the mnemonic is a classic exam pitfall. ### Clinical Pearl During lung surgery or hilum dissection, the surgeon encounters the **pulmonary vein first** (most anterior), then the artery, and finally the bronchus (most posterior). This anatomical knowledge prevents inadvertent injury to vital structures. ### Left vs. Right Hilum On the **left side**, the arrangement from superior to inferior (rather than anterior to posterior) is: Artery (superior), Bronchus (posterior), Pulmonary veins (inferior/anterior). The right hilum follows the classic PAB anterior-to-posterior rule more consistently. The left hilum is also higher than the right due to the cardiac notch. **Reference:** BD Chaurasia's Human Anatomy, Vol. 1 (Thorax); Gray's Anatomy, 41st edition — Mediastinum and Lung Hilum.