Мұрын қуысының қабыршақты сүйектері

Piece of bone in the breathing passage of humans and other animals

In anatomy, a nasal concha ('/k//ɒ//n//k//ə/; : conchae; '/k//ɒ//n//k//iː/; Latin for 'shell'), also called a nasal turbinate or turbinal, is a long, narrow, curled shelf of bone that protrudes into the breathing passage of the nose in humans and various other 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. In humans, the conchae divide the nasal airway into four groove like air passages, and are responsible for forcing inhaled air to flow in a steady, regular pattern around the largest possible surface area of nasal mucosa. As a ciliated mucous membrane with shallow blood supply, the nasal mucosa cleans and warms the inhaled air in preparation for the lungs. A rapidly dilating arteriolar circulation to these bones may lead to a sharp increase in the pressure within, in response to acute cooling of the body core. The pain from this pressure is often referred to as "brain freeze", and is frequently associated with the rapid consumption of ice cream. The shallowness of the venous blood supply of the mucosa contributes to the ease with which nosebleed can occur.

Conchae are composed of pseudostratified columnar, ciliated respiratory epithelium with a thick, vascular, and erectile glandular tissue layer. 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. The middle conchae are smaller but have the most complex anatomy of the nasal turbinates. They originate from the lateral edge of the cribriform plate of the ethmoid bone. They insert anteriorly into the frontal process of the maxilla and posteriorly into the perpendicular plate of the palatine bone. There are three mutually perpendicular segments of the middle turbinate: from proximal to distal, there is the horizontal segment (axial plane), the basal lamella (coronal plane), and the vertical segment (sagittal plane). 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. There is sometimes a pair of supreme conchae superior to the superior conchae. When present, these usually take the form of a small crest.

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. Treatment of the underlying allergy or irritant may reduce turbinate swelling. In cases that do not resolve, or for treatment of deviated septum, turbinate surgery may be required.

Turbinate reduction is a surgery to reduce the size of the turbinates (typically inferior turbinates). There are different techniques, including bipolar radiofrequency ablation (also known as somnoplasty), electrocautery, and use of cold steel instruments (eg, microdebrider). Turbinectomy is a surgery to remove the turbinates (typically inferior turbinates). In the case of turbinate reduction, only small amounts of turbinate tissue are removed because the turbinates are essential for respiration. Turbinectomy is usually reserved for patients who have persistent symptoms despite previous turbinate reduction surgery. Risks of reduction of the inferior or middle turbinates include empty nose syndrome. Concha bullosa is an abnormal pneumatization of the middle turbinate, which may interfere with normal ventilation of the sinus ostia and can result in recurrent sinusitis. In some cases, the concha bullosa may be resected to help resolve persistent symptoms.

Generally, in animals, nasal conchae are convoluted structures of thin bone or cartilage located in the nasal cavity. These are lined with mucous membranes that can perform two functions. They can improve the sense of smell by increasing the area available to absorb airborne chemicals, and they can warm and moisten inhaled air, and extract heat and moisture from exhaled air to prevent desiccation of the lungs. Olfactory turbinates are found in all living tetrapods, and respiratory turbinates are found in most mammals and birds. Animals with respiratory turbinates can breathe faster without drying out their lungs, and consequently can have a faster metabolism. Dogs and other canids possess well developed nasal turbinates. These turbinates allow for heat exchange between small arteries and veins on their maxilloturbinate (turbinates positioned on maxilla bone) surfaces in a counter current heat exchange system. The water conservation and thermoregulatory capabilities of these well developed turbinates in dogs may have been crucial adaptations that allowed dogs (including both domestic dogs and their wild prehistoric gray wolf ancestors) to survive in the harsh Arctic environment and other cold areas of northern Eurasia and North America, which are both very dry and very cold. While the maxilloturbinates of mammals are located in the path of airflow to collect moisture, sensory turbinates in both mammals and reptiles are positioned farther back and above the nasal passage, away from the flow of air. Glanosuchus has ridges positioned low in the nasal cavity, indicating that it had maxilloturbinates that were in the direct path of airflow. The maxilloturbinates may not have been preserved because they were either very thin or cartilaginous. The possibility has also been raised that these ridges are associated with an olfactory epithelium rather than turbinates. Nonetheless, the possible presence of maxilloturbinates suggests that Glanosuchus may have been able to rapidly breathe without drying out the nasal passage, and therefore could have been an endotherm. But there is indirect evidence for their presence in some fossils. Rudimentary ridges like those that support respiratory turbinates have been found in advanced Triassic cynodonts, such as Thrinaxodon and Diademodon. This suggests that they may have had fairly high metabolic rates. The paleontologist John Ruben and others have argued that no evidence of nasal turbinates has been found in dinosaurs. All the dinosaurs they examined had nasal passages that they claimed were too narrow and too short to accommodate nasal turbinates, so dinosaurs could not have sustained the breathing rate required for a mammal like or bird like metabolic rate while at rest, because their lungs would have dried out. However, objections have been raised against this argument. Nasal turbinates are absent or very small in some birds, such as ratites, Procellariiformes and Falconiformes. They are also absent or very small in some mammals, such as anteaters, bats, elephants, whales and most primates, although these animals are fully endothermic and in some cases very active. Furthermore, ossified turbinate bones have been identified in the ankylosaurid dinosaur Saichania.