Specific Positioning of the Horizontal Fissure in the Right Pulmonary Organ

Description

Arcing transversely across the right lung, the horizontal (minor) fissure runs from the anterior border toward the posterior aspect, dividing the superior lobe above from the middle lobe below. Its course lies superior to the oblique (major) fissure and meets it laterally, creating the familiar three-lobed organization unique to the right pulmonary organ. Medially, the fissural plane approaches the hilum, where it relates to the root of the lung and the branching pattern of the lobar bronchi, even when the fissure itself does not fully reach the mediastinal surface. A shallow groove. It is the fissura horizontalis. Correct identification of the minor fissure matters because its completeness and position vary, and that variation changes how disease spreads and how surgeons plan resection margins. On chest CT and radiography, the horizontal fissure can appear as a thin line or may be incomplete, a common source of confusion when localizing right upper lobe versus right middle lobe atelectasis or segmental pneumonia. During right middle lobectomy or VATS approaches, an incomplete fissure increases the risk of prolonged postoperative air leak, so preoperative understanding of fissural anatomy and the “fissureless” technique often hinges on this exact landmark. Use this illustration in gross anatomy and respiratory system teaching to anchor lobe-based localization, and in radiology or thoracic surgery publications where accurate fissure terminology (minor, horizontal, transverse fissure) avoids ambiguous “upper lung” descriptions. It also supports patient-facing diagrams that explain why a right-sided lobectomy may involve three lobes but different fissural planes than the left lung. Anatomical accuracy verified by SciePro's Medical Advisory Board.