Lateral Segmental Artery of the Right Lung

Description

Arising from the right pulmonary artery, the lateral segmental artery (A4) courses anterolaterally into the middle lobe, running with the segmental bronchus (B4) and draining toward the subpleural capillary bed of the lateral segment. More medially, the pulmonary trunk bifurcates and the right pulmonary artery passes posterior to the ascending aorta and superior vena cava before giving lobar and segmental branches. Pulmonary veins return oxygenated blood from the middle lobe toward the left atrium, typically occupying a more anterior and inferior position than the accompanying segmental arteries within the hilum. Nearby, the trachea with its C-shaped cartilaginous rings descends superior to the heart and divides at the carina into the main bronchi. Segmental arterial anatomy matters because it maps directly to surgical planes and oncologic resection strategy in the right lung. During a right middle lobectomy or a segmentectomy aimed at the lateral segment, A4 is a named target for individual ligation or stapling, and confusion with adjacent branches (often A5 to the medial segment or an early branching pattern from the interlobar pulmonary artery) can lead to ischemia of preserved parenchyma or troublesome bleeding at the hilum. Variants are common. Preoperative CT angiography and intraoperative dissection both depend on this exact branching logic. Use this illustration for teaching bronchopulmonary segments in gross anatomy, cardiopulmonary blocks, and thoracic surgery training, or for figure panels in papers on segmentectomy planning, pulmonary artery anatomy, or right hilar dissection. It also suits patient-facing education when explaining why a “segment” can be removed without taking the entire lobe. Anatomical accuracy verified by SciePro's Medical Advisory Board.