Each pair is composed of one concha in either side of the nasal cavity, divided by the septum.The superior conchae are smaller structures, connected to the middle conchae by nerve-endings, and serve to protect the olfactory bulb. The openings to the posterior ethmoidal sinuses exist under the superior meatus.The middle conchae are smaller. In humans, they are usually as long as the little finger. They project downwards over the openings of the maxillary and anterior and middle ethmoid sinuses, and act as buffers to protect the sinuses from coming in direct contact with pressurized nasal airflow. Most inhaled airflow travels between the inferior concha and the middle meatus.The inferior conchae are the largest, and can be as long as the index finger in humans, and are responsible for the majority of airflow direction, humidification, heating, and filtering of air inhaled through the nose.The inferior conchae are graded 1–4 based on the inferior concha classification system (known as the inferior turbinate classification system) in which the total amount of the airway space that the inferior concha takes up is estimated. Grade 1 is 0–25% of the airway, grade 2 is 26–50% of the airway, grade 3 is 51–75% of the airway and grade 4 is 76–100% of the airway.There is sometimes a pair of supreme conchae superior to the superior conchae. When present, these usually take the form of a small crest. Function
The conchae comprise most of the mucosal tissue of the nose and are required for functional respiration.
They are enriched with airflow pressure and temperature-sensing nerve receptors (linked to the trigeminal nerve route, the fifth cranial nerve), allowing for tremendous erectile capabilities of nasal congestion and decongestion, in response to the weather conditions and changing needs of the body. In addition, the erectile tissue undergoes an often unnoticed cycle of partial congestion and decongestion called the nasal cycle. The flow of blood to the nasal mucosa in particular the venous plexus of the conchae is regulated by the pterygopalatine ganglion and heats or cools the air in the nose. The nasopulmonary and nasothoracic reflexes regulate the mechanism of breathing through deepening of inhalation. Triggered by the flow of the air, the pressure of the air in the nose, and the quality of the air, impulses from the nasal mucosa are transmitted by the trigeminal nerve to the breathing centres in the brainstem, and the generated response is transmitted to the bronchi, the intercostal muscles, and the diaphragm. The conchae are also responsible for filtration, heating, and humidification of air inhaled through the nose. Of these three, filtration is achieved mostly by other more effective means such as mucous and cilia. As air passes over the conchae, it is heated to 32–34 °C (89–93 °F), humidified (up to 98% water saturation) and filtered. Immunological role
The respiratory epithelium that covers the erectile tissue (or lamina propria) of the conchae plays a major role in the bodys first line of immunological defense. The respiratory epithelium is partially composed of mucus-producing goblet cells.