where does the fluid come from when you have a runny nose
Rhinorrhea Rhinorrhea is characterized by an excess amount of mucus produced by the mucous membranes that line the nasal cavities. The membranes create mucus faster than it can be processed, causing a backup of mucus in the nasal cavities. As the cavity fills up, it blocks off the air passageway, causing difficulty breathing through the nose. Air caught in nasal cavities, namely the sinus cavities, cannot be released and the resulting pressure may cause a headache or facial pain. If the sinus passage remains blocked, there is a chance that sinusitis may result.[4] If the mucus backs up through the Eustachian tube, it may result in ear pain or an ear infection. Excess mucus accumulating in the throat or back of the nose may cause a post-nasal drip, resulting in a sore throat or coughing.[4] Additional symptoms include sneezing, nosebleeds, and nasal discharge.[5]
Nasal cavity The two nasal cavities condition the air to be received by the other areas of the respiratory tract. Owing to the large surface area provided by the nasal conchae (also known as turbinates), the air passing through the nasal cavity is warmed or cooled to within 1 degree of body temperature. In addition, the air is humidified, and dust and other particulate matter is removed by vibrissae, short, thick hairs, present in the vestibule. The entire mucosa of the nasal fossae is covered by a blanket of mucus, which lies superficial to the microscopic cilia and also filters inspired air. The cilia of the respiratory epithelium move the secreted mucus and particulate matter posteriorly towards the pharynx where it passes into the esophagus and is digested in the stomach. The nasal cavity also houses the sense of smell and contributes greatly to taste sensation through its posterior communication with the mouth via the choanae.