Paranasaalit

Paranasaalit, also known as paranasal sinuses, are a group of air-filled cavities within the bones surrounding the nasal cavity. The four principal sinuses are the maxillary, frontal, ethmoid, and sphenoid sinuses. The ethmoid sinuses consist of a network of small air cells between the nose and the eyes. These cavities are connected to the nasal cavity by small openings called ostia.

Anatomy and drainage: Each sinus is lined by a mucous membrane and communicates with the nasal cavity to drain mucus. The maxillary and frontal sinuses drain into the middle meatus, while the ethmoid air cells drain into both the middle and superior meatuses. The sphenoid sinus drains into the sphenoethmoidal recess. Drainage and ventilation depend on mucociliary clearance, and obstruction of the ostia can impair this process.

Structure and development: The mucous membrane of the paranasaalit is pseudostratified ciliated columnar epithelium with goblet cells. Pneumatization begins before birth for some sinuses and continues through childhood, with the maxillary sinus usually present at birth and others enlarging during growth. Size and shape vary among individuals.

Function and clinical relevance: The sinuses help reduce skull weight, provide insulation, and contribute to the conditioning of inspired air. They also play a role in voice resonance and mucosal defense. Clinically, the paranasal sinuses are a common site of infection or inflammation (sinusitis). Obstruction of drainage pathways, anatomical variations such as concha bullosa or a deviated septum, and chronic inflammation can affect sinus function. Imaging, especially CT, is used to assess anatomy and pathology.