The normal nostrils are separated into two nostrils by the middle nasal septum, and most of the septum is straight and not deviated in the middle to keep the balance of nasal ventilation on both sides. The structure of the nasal cavity is the same on both sides, and there are turbinates in the nasal cavity. The inferior turbinates are located at the front of the nasal cavity, and the middle turbinates and the superior turbinates are located upwards in order, and the size of each turbinate is reduced by about 1/3, and the areas below the respective turbinates are called the inferior, middle and superior nasal tracts. The source of sinusitis can be determined by the presence of more purulent secretions in the middle nasal tract, and the posterior nostril may have a rounded occipital and pharyngeal crypt.