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In
anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
, a nasal concha (), plural conchae (), also called a nasal turbinate or turbinal, is a long, narrow, curled shelf of
bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...
that protrudes into the breathing passage of the
nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes th ...
in humans and various animals. The conchae are shaped like an elongated
seashell A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washe ...
, which gave them their name (Latin ''concha'' from Greek ''κόγχη''). A concha is any of the scrolled spongy
bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...
s of the
nasal passages The human nose is the most protruding part of the face. It bears the nostrils and is the first organ of the respiratory system. It is also the principal organ in the olfactory system. The shape of the nose is determined by the nasal bones ...
in
vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s.''Anatomy of the Human Body''
Gray, Henry (1918) The Nasal Cavity.
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 The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc ...
of
nasal mucosa The nasal mucosa lines the nasal cavity. It is part of the respiratory mucosa, the mucous membrane lining the respiratory tract. The nasal mucosa is intimately adherent to the periosteum or perichondrium of the nasal conchae. It is continuous w ...
. As a
ciliated The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...
mucous membrane with shallow blood supply, the nasal mucosa cleans and warms the inhaled air in preparation for the
lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s. 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 A cold-stimulus headache, colloquially known as an ice-cream headache or brain freeze, is a form of brief pain or headache commonly associated with consumption (particularly quick consumption) of cold beverages or foods such as ice cream, Popsic ...
", and is frequently associated with the rapid consumption of
ice cream Ice cream is a sweetened frozen food typically eaten as a snack or dessert. It may be made from milk or cream and is flavoured with a sweetener, either sugar or an alternative, and a spice, such as cocoa or vanilla, or with fruit such as str ...
. The shallowness of the venous blood supply of the mucosa contributes to the ease with which
nosebleed A nosebleed, also known as epistaxis, is bleeding from the nose. Blood can flow down into the stomach, and cause nausea and vomiting. In more severe cases, blood may come out of both nostrils. Rarely, bleeding may be so significant that low bloo ...
can occur.


Structure

Conchae are composed of pseudostratified
columnar Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
,
ciliated The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...
respiratory epithelium Respiratory epithelium, or airway epithelium, is a type of ciliated columnar epithelium found lining most of the respiratory tract as respiratory mucosa, where it serves to moisten and protect the airways. It is not present in the vocal cords o ...
with a thick,
vascular The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...
, and erectile
glandular In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...
tissue layer.Turbinate Dysfunction: Focus on the role of the inferior turbinates in nasal airway obstruction.
S.S. Reddy, et al. ''Grand Rounds Presentation, UTMB, Dept. of Otolaryngology''
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 In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatri ...
. The '' superior conchae'' are smaller structures, connected to the middle conchae by nerve-endings, and serve to protect the
olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a grey matter, neural structure of the vertebrate forebrain involved in olfaction, the sense of odor, smell. It sends olfactory information to be further processed in the amygdala, the orbitof ...
. 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 The little finger, or pinkie, also known as the baby finger, fifth digit, or pinky finger, is the most ulnar and smallest digit of the human hand, and next to the ring finger. Etymology The word "pinkie" is derived from the Dutch word ''pink ...
. 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 The index finger (also referred to as forefinger, first finger, second finger, pointer finger, trigger finger, digitus secundus, digitus II, and many other terms) is the second digit of a human hand. It is located between the thumb and the mid ...
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 A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
tissue of the
nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes th ...
and are required for functional
respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...
. They are enriched with airflow pressure and temperature-sensing nerve receptors (linked to the
trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewin ...
route, the fifth cranial nerve), allowing for tremendous erectile capabilities of
nasal congestion Nasal congestion is the blockage of nasal breathing usually due to membranes lining the nose becoming swollen from inflamed blood vessels. Background In about 85% of cases, nasal congestion leads to mouth breathing rather than nasal breathing. ...
and decongestion, in response to the
weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...
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 nasal cycle is the unconscious alternating partial congestion and decongestion of the nasal cavities in humans and other animals. This results in greater airflow through one nostril with periodic alternation between the nostrils. It is a ph ...
. The flow of blood to the nasal mucosa in particular the venous plexus of the conchae is regulated by the
pterygopalatine ganglion The pterygopalatine ganglion (aka Meckel's ganglion, nasal ganglion, or sphenopalatine ganglion) is a parasympathetic ganglion found in the pterygopalatine fossa. It is largely innervated by the greater petrosal nerve (a branch of the facial ne ...
and heats or cools the air in the nose. The nasopulmonary and nasothoracic
reflex In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
es 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 The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...
, and the generated response is transmitted to the
bronchi A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchus. ...
, the
intercostal muscle Intercostal muscles are many different groups of muscles that run between the ribs, and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping expand and shrink the size of ...
s, and the diaphragm. The conchae are also responsible for
filtration Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter ...
, 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 Water content or moisture content is the quantity of water contained in a material, such as soil (called soil moisture), rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as ...
) and filtered.


Immunological role

The
respiratory epithelium Respiratory epithelium, or airway epithelium, is a type of ciliated columnar epithelium found lining most of the respiratory tract as respiratory mucosa, where it serves to moisten and protect the airways. It is not present in the vocal cords o ...
that covers the erectile tissue (or
lamina propria The lamina propria is a thin layer of connective tissue that forms part of the moist linings known as mucous membranes or mucosae, which line various tubes in the body, such as the respiratory tract, the gastrointestinal tract, and the urogenita ...
) of the conchae plays a major role in the body's first line of
immunological Immunology is a branch of medicineImmunology for Medical Students, Roderick Nairn, Matthew Helbert, Mosby, 2007 and biology that covers the medical study of immune systems in humans, animals, plants and sapient species. In such we can see there ...
defense. The
respiratory epithelium Respiratory epithelium, or airway epithelium, is a type of ciliated columnar epithelium found lining most of the respiratory tract as respiratory mucosa, where it serves to moisten and protect the airways. It is not present in the vocal cords o ...
is partially composed of
mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
-producing goblet cells. This secreted mucus covers the nasal cavities, and serves as a filter, by trapping air-borne particles larger than 2 to 3
micrometers The micrometre (American and British English spelling differences#-re, -er, international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American and British English spelling differences# ...
. The respiratory epithelium also serves as a means of access for the
lymphatic system The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid o ...
, which protects the body from being infected by viruses or bacteria.


Smell

The conchae provide, first and foremost, the humidity needed to preserve the delicate
olfactory epithelium The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smell. In humans, it measures 9 cm2 and lies on the roof of the nasal cavity about 7 cm above and behind the nostrils. The olfactory ...
, which in turn is needed to keep the olfactory receptors healthy and alert. If the epithelial layer gets dry or irritated, it may cease to function. This is usually a temporary condition but, over time, may lead to chronic
anosmia Anosmia, also known as smell blindness, is the loss of the ability to detect one or more smells. Anosmia may be temporary or permanent. It differs from hyposmia, which is a decreased sensitivity to some or all smells. Anosmia can be due to a nu ...
. The turbinates also increase the
surface area The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc ...
of the inside of the nose, and, by directing and deflecting airflow across the maximum mucosal surface of the inner nose, they are able to propel the inspired air. This, coupled with the humidity and filtration provided by the conchae, helps to carry more scent molecules towards the higher, and very narrow regions of the nasal airways, where olfaction nerve receptors are located. The superior conchae completely cover and protect the nerve axons piercing through the
cribriform plate In mammalian anatomy, the cribriform plate (Latin for lit. ''sieve-shaped''), horizontal lamina or lamina cribrosa is part of the ethmoid bone. It is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities. It supp ...
(a porous bone plate that separates the nose from the brain) into the nose. Some areas of the middle conchae are also
innervate A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
d by the olfactory bulb. All three pairs of conchae are innervated by
pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...
and
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
receptors, via the
trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewin ...
(or, the fifth
cranial nerve Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and ...
). Research has shown that there is a strong connection between these nerve endings and activation of the olfactory receptors, but science has yet to fully explain this interaction.


Clinical significance


Dysfunction

Large, swollen conchae, often referred to clinically as turbinates, may lead to blockage of nasal breathing.
Allergies Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...
, exposure to environmental irritants, or a persistent
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
within the sinuses can lead to turbinate swelling. Deformity of the
nasal septum The nasal septum () separates the left and right airways of the Human nose, nasal cavity, dividing the two nostrils. It is Depression (kinesiology), depressed by the depressor septi nasi muscle. Structure The fleshy external end of the nasal ...
can also result in enlarged turbinates.Reduction/Removal of the Inferior Turbinate
From the Sinus Info Center.
Treatment of the underlying allergy or irritant may reduce turbinate swelling. In cases that do not resolve, or for treatment of
deviated septum Nasal septum deviation is a physical disorder of the nose, involving a displacement of the nasal septum. Some displacement is common, affecting 80% of people, mostly without their knowledge. Signs and symptoms The nasal septum is the bone and ...
, turbinate surgery may be required.


Surgery

Turbinectomy A turbinectomy or turbinoplasty (preserving the mucosal layer) is a surgical procedure, that removes tissue, and sometimes bone, of the turbinates in the nasal passage, particularly the inferior nasal concha. The procedure is usually performed t ...
is a surgery for the reduction or removal of the turbinates. There are different techniques, including bipolar radiofrequency ablation, also known as
somnoplasty Somnoplasty is a trademark by Somnus Medical Technologies used for its radiofrequency ablation medical devices cleared by the Food and Drug Administration (FDA) to treat habitual snoring, chronic nasal obstruction, and obstructive sleep apnea (OSA) ...
; reduction by the use of pure heat; and turbinate sectioning. In the case of sectioning, only small amounts of turbinate tissue are removed because the turbinates are essential for respiration. Risks of reduction of the inferior or middle turbinates include
empty nose syndrome Empty may refer to: ‍ Music Albums * ''Empty'' (God Lives Underwater album) or the title song, 1995 * ''Empty'' (Nils Frahm album), 2020 * ''Empty'' (Tait album) or the title song, 2001 Songs * "Empty" (The Click Five song), 2007 * ...
. Dr. Houser: "this is especially true in cases of anterior inferior turbinate (IT) resection because of its important role in the internal nasal valve."Houser SM. Surgical Treatment for Empty Nose Syndrome. Archives of Otolaryngology Head & Neck Surgery\ Vol 133 (No.9) Sep' 2007: 858–863.
Concha bullosa A concha bullosa is a pneumatized (air-filled) cavity within a nasal concha, also known as a ''turbinate''. Bullosa refers to the air-filled cavity within the turbinate. It is a normal anatomic variant seen in up to half the population. Occasional ...
is an abnormal pneumatization of the middle turbinate, which may interfere with normal ventilation of the sinus ostia and can result in recurrent
sinusitis Sinusitis, also known as rhinosinusitis, is inflammation of the nasal mucosa, mucous membranes that line the paranasal sinuses, sinuses resulting in symptoms that may include thick Mucus#Respiratory system, nasal mucus, a nasal congestion, plugg ...
.


Other animals

Generally, in animals, nasal conchae are convoluted structures of thin bone or cartilage located in the
nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nasal c ...
. These are lined with
mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
s 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 Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...
of the lungs.
Olfactory The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it ...
turbinates are found in all living
tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...
s, and
respiratory The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
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. For example, when the
emu The emu () (''Dromaius novaehollandiae'') is the second-tallest living bird after its ratite relative the ostrich. It is endemic to Australia where it is the largest native bird and the only extant member of the genus ''Dromaius''. The emu' ...
exhales, its nasal turbinates condense moisture from the air and absorbs it for reuse.
Dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s and other
canid Canidae (; from Latin, '' canis'', " dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found withi ...
s possess well-developed nasal turbinates.Wang (2008) p. 88. These turbinates allow for heat exchange between small arteries and veins on their maxilloturbinate (turbinates positioned on
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
bone) surfaces in a counter-current heat-exchange system. Dogs are capable of prolonged chases, in contrast to the ambush predation of cats, and these complex turbinates play an important role in enabling this (cats only possess a much smaller and less-developed set of nasal turbinates). This same complex turbinate structure help conserve water in arid environments.Wang (2008) p. 87. 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 The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly ...
ancestors) to survive in the harsh
Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
environment and other cold areas of northern Eurasia and North America, which are both very dry and very cold.
Reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s and more primitive
synapsid Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptil ...
s have olfactory turbinates that are involved in sensing smell rather than preventing desiccation. 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 ''Glanosuchus'' is a genus of scylacosaurid therocephalian from the Late Permian of South Africa. The type species ''G. macrops'' was named by Robert Broom in 1904. ''Glanosuchus'' had a middle ear structure that was intermediate between that of ...
'' 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 Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck and ...
. The possibility has also been raised that these ridges are associated with an olfactory
epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
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. The bones of nasal turbinates are very fragile and seldom survive as fossils. In particular none have been found in fossil birds. 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
cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...
s, such as ''
Thrinaxodon ''Thrinaxodon'' is an extinct genus of cynodonts, most commonly regarded by its species ''T. liorhinus'' which lived in what are now South Africa and Antarctica during the Early Triassic. ''Thrinaxodon'' lived just after the Permian–Triassic m ...
'' and ''
Diademodon ''Diademodon'' is an extinct genus of cynodonts. It was about long. Discovery Harry Seeley had found his fossil in the Burgersdorp Formation of the Beaufort Group in the Karoo Basin of South Africa. As late as 1988, ''Diademodon'' had bee ...
''. This suggests that they may have had fairly high metabolic rates. The paleontologist
John Ruben John A. Ruben is a researcher in Zoology and Vertebrate paleontology at the Oregon State University in Corvallis. Much of his published research is focused on studying the respiratory system in birds, in order to contradict the theory of theropod ...
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
ratite A ratite () is any of a diverse group of flightless, large, long-necked, and long-legged birds of the infraclass Palaeognathae. Kiwi, the exception, are much smaller and shorter-legged and are the only nocturnal extant ratites. The systematics ...
s,
Procellariiformes Procellariiformes is an order of seabirds that comprises four families: the albatrosses, the petrels and shearwaters, and two families of storm petrels. Formerly called Tubinares and still called tubenoses in English, procellariiforms are of ...
and
Falconiformes The order Falconiformes () is represented by the extant family Falconidae (falcons and caracaras) and a handful of enigmatic Paleogene species. Traditionally, the other bird of prey families Cathartidae (New World vultures and condors), Sagitt ...
. 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 Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known Ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Pal ...
dinosaur ''
Saichania ''Saichania'' (Mongolian meaning "beautiful one") is a genus of herbivorous ankylosaurid dinosaur from the Late Cretaceous period of Mongolia and China. The first fossils of ''Saichania'' were found in the early 1970s in Mongolia. In 1977 the ...
''.


See also


Additional images

Image:Concha nasalis.gif, Nasal conchae: Blocked/free Image:NormalNose-CT-Front-cross-section-common-wiki.jpg, Normal Nose CT Front cross section Image:Gray859.png, Coronal section of nasal cavities. Image:Right-nasal-airway-passage.jpg, Right nasal airway passage Image:Nasenmuscheln1.JPG, Nasal conchae File:Nasal cavity - anterior view.jpg, Nasal concha


Notes


References

* Wang, Xiaoming (2008
''Dogs: Their Fossil Relatives and Evolutionary History''
Columbia University Press. . {{DEFAULTSORT:Nasal Concha Skeletal system Olfaction Irregular bones