Nasal concha

also called a nasal turbinate or turbinal,[1][2] is a long, narrow, curled shelf of bone that protrudes into the breathing passage of the nose in humans and various animals. The conchae are shaped like an elongated seashell, which gave them their name (Latin concha from Greek κόγχη). A concha is any of the scrolled spongy bones of the nasal passages in vertebrates.[3]

Conchae are composed of pseudostratified columnar, ciliated respiratory epithelium with a thick, vascular, and erectile glandular tissue layer.[4] The conchae are located laterally in the nasal cavities, curling medially and downward into the nasal airway. Each pair is composed of one concha in either side of the nasal cavity, divided by the septum.[4]

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.[3]

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.[3]

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.[3]

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.[5]

There is sometimes a pair of supreme conchae superior to the superior conchae. When present, these usually take the form of a small crest