by Jason Wasserman MD PhD FRCPC
June 5, 2022
When we breathe, air enters our body through our nose and mouth and travels down a long tube called the trachea into our lungs. The inside of the nose is called the nasal cavity and it helps to warm and clean the air before it reaches our lungs.
The nasal cavity is surrounded by small paired air-filled spaces called paranasal sinuses that connect to the nasal cavity by small openings. The paranasal sinuses include the maxillary sinus, frontal sinus, ethmoid sinus, and sphenoid sinus. Because the nasal cavity and sinuses are connected to each other, pathologists describe this area of the body as the sinonasal tract.
The inside of the nasal cavity and the sinuses are lined by specialized epithelial cells that form a barrier called the epithelium. The tissue underneath the epithelium is called stroma and it is made up of blood vessels and small round structures called glands that make a substance called mucin. The epithelium and underlying stroma combine to create a layer of tissue called sinonasal mucosa.