A lung fissure is an anatomical feature within the human respiratory system. These fissures are deep grooves or folds that divide the lungs into distinct sections called lobes. They are made up of double layers of pleura, which are thin membranes that line the lungs and the inside of the chest cavity. These divisions contribute to the overall structure and efficiency of the lungs.
Anatomy and Function of Lung Fissures
The lungs have a lobar structure. The right lung has three lobes: a superior (upper), middle, and inferior (lower) lobe. These are separated by two fissures. The oblique fissure, the major fissure, separates the inferior lobe from the middle and superior lobes. The horizontal fissure, the minor fissure, is unique to the right lung and divides the superior lobe from the middle lobe.
The left lung has two lobes: a superior and an inferior lobe. These two lobes are separated by a single oblique fissure. The fissures act as natural boundaries, allowing each lung lobe to expand and contract independently during breathing.
Common Fissure Variations
Variations in lung fissures are common. One such variation is an “incomplete fissure,” which means the fissure does not fully separate the lung lobes. An incomplete horizontal fissure can occur in the right lung. An incomplete oblique fissure can also occur in both the left and right lungs.
Another type of variation is an “accessory fissure,” an extra fissure that creates additional small subdivisions within a lobe. These are considered normal anatomical variants. Common accessory fissures include the azygos fissure, along with superior and inferior accessory fissures, and a left horizontal fissure. Accessory fissures are common.
Clinical Importance of Lung Fissures
Lung fissures serve as landmarks for medical professionals, especially when interpreting medical imaging. On chest X-rays and CT scans, these fissures help radiologists locate abnormalities within the lungs, such as pneumonia, tumors, or collapsed lung segments. This precise localization is valuable for diagnosis and treatment planning.
Understanding fissure anatomy is also helpful for surgeons. In cases requiring surgical removal of a lung lobe (lobectomy) or a smaller segment (segmentectomy), knowledge of fissure completeness and variations can influence the surgical approach. For instance, an incomplete fissure might present technical challenges during surgery or could affect how an infection spreads between lobes. Recognizing these variations allows healthcare providers to better prepare for procedures and interpret the spread of lung diseases.