A 48-year-old woman undergoes CT chest for evaluation of a solitary nodule in the left lower lobe. The radiologist reports the lesion to be in the superior segment of the left lower lobe. The pulmonologist plans a segmental resection. Which of the following statements correctly describes the bronchial and vascular supply to this segment?

Explanation

## Bronchial and Vascular Supply of the Superior Segment (Left Lower Lobe) **Key Point:** Each bronchopulmonary segment is defined by its own **secondary (segmental) bronchus**, **segmental artery**, and **segmental vein**. The superior segment of the left lower lobe receives a single secondary bronchus and is accompanied by a segmental pulmonary artery, with venous drainage via the **superior pulmonary vein** (not the inferior vein, despite being in the lower lobe). ### Anatomical Definition of a Bronchopulmonary Segment **High-Yield:** A bronchopulmonary segment is the **functional unit of the lung** defined by: 1. **One secondary (segmental) bronchus** — the structural basis 2. **One segmental pulmonary artery** — accompanies the bronchus 3. **Segmental veins** — drain the segment (course intersegmentally, NOT within the segment) 4. **Visceral pleura** — forms the boundary ### Venous Drainage Pattern — Critical Distinction **Clinical Pearl:** Segmental **arteries run WITH the bronchus** (centripetal), but segmental **veins run BETWEEN segments** (intersegmental) and drain to lobar veins. The superior segment of the left lower lobe drains to the **superior pulmonary vein** because it is located in the upper portion of the lower lobe and its venous drainage follows the superior vein pathway. **Mnemonic: "Artery with Bronchus, Vein between segments"** — **A**rtery **W**ith **B**ronchus; **V**ein **B**etween. ### Left Lower Lobe Segmentation | Segment | Secondary Bronchus | Segmental Artery | Venous Drainage | |---------|-------------------|------------------|------------------| | **Superior** | One | One | Superior pulmonary vein | | **Medial basal** | One | One | Inferior pulmonary vein | | **Anterior basal** | One | One | Inferior pulmonary vein | | **Lateral basal** | One | One | Inferior pulmonary vein | | **Posterior basal** | One | One | Inferior pulmonary vein | **Key Point:** The **superior segment is unique** in the lower lobe because its venous drainage is to the **superior** pulmonary vein, not the inferior vein. This is because of its anatomical position and the course of its draining veins. ### Surgical Significance **Tip:** During segmentectomy, the surgeon must: 1. Identify and divide the **segmental bronchus** (defines the segment) 2. Divide the **segmental artery** (prevents bleeding) 3. Preserve intersegmental veins (they drain adjacent segments) 4. Ensure the **intersegmental plane** is correctly identified (usually by inflation-deflation technique) This anatomical knowledge prevents inadvertent injury to adjacent segments and ensures adequate lymph node clearance in cancer surgery.