The septum is a structure made of bone and cartilage that divides the nasal airway. The septum is covered by mucous membranes that are full of blood vessels. About 80% of people have a mild septum deformity or crookedness that makes one nasal passage larger than the other. For most, the symptoms are mild enough that they may not even be noticeable. For some, however, a significantly deviated septum can lead to lifestyle impediments.