Most of the air you breathe moves through a narrow space between the wall of your nose (the septum) and the lower scroll-shaped structure inside the nose (the inferior turbinate). A common cause of a blocked nose is a crooked septum, called a deviated septum. This view shows the inside of the nose with the outer nose removed. If the septum bends to one side, it narrows the air space on that side. The picture also shows a ridge of bone that can narrow the opposite side.