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 fossae.[1] Each fossa is the continuation of one of the two nostrils. The nasal cavity is the uppermost part of the respiratory system and provides the nasal passage for inhaled air from the nostrils to the nasopharynx and rest of the respiratory tract.

The paranasal sinuses surround and drain into the nasal cavity.

Nasal cavity
Illu01 head neck
Head and neck.
Illu conducting passages
Conducting passages
Details
Part ofNose
Identifiers
Latincavum nasi; cavitas nasi
MeSHD009296
TAA06.1.02.001
FMA54378
Anatomical terminology

Structure

The term "nasal cavity" can refer to each of the two fossae of the nose, or to the two sides combined.

CT of the ostiomeatal complex, coronal plane, with annotations
CT scan in the coronal plane, showing the ostiomeatal complex (green area).

The lateral wall of each nasal cavity mainly consists of the maxilla. However, there is a deficiency that is compensated by the perpendicular plate of the palatine bone, the medial pterygoid plate, the labyrinth of ethmoid and the inferior concha. The paranasal sinuses are connected to the nasal cavity through small orifices called ostia. Most of these ostia communicate with the nose through the lateral nasal wall, via a semi-lunar depression in it known as the semilunar hiatus. The hiatus is bound laterally by a projection known as the uncinate process. This region is called the ostiomeatal complex.[2]

The roof of each nasal cavity is formed in its upper third to one half by the nasal bone and more inferiorly by the junctions of the upper lateral cartilage and nasal septum. Connective tissue and skin cover the bony and cartilaginous components of the dorsum of the nose.

The floor of the nasal cavities, which also form the roof of the mouth, is made up by the bones of the hard palate: the horizontal plate of the palatine bone posteriorly and the palatine process of the maxilla anteriorly. To the front of the nasal cavity is the nasal vestibule and external opening, while the back blends, via the choanae, into the nasopharynx.

The nasal cavity is divided in two by the vertical nasal septum. On the sides of the nasal cavity are three horizontal outgrowths called nasal conchae (singular "concha") or turbinates. These turbinates disrupt the airflow, directing air toward the olfactory epithelium on the surface of the turbinates and the septum. The vomeronasal organ is located at the back of the septum and has a role in pheromone detection.

Segments

The nasal cavity is divided into two segments: the respiratory segment and the olfactory segment.

  • The respiratory segment comprises most of each nasal fossa and is lined with ciliated pseudostratified columnar epithelium (also called respiratory epithelium). The conchae, or turbinates, are located in this region. The turbinates have a very vascularized lamina propria (erectile tissue) allowing the venous plexuses of their mucosa to engorge with blood, restricting airflow and causing air to be directed to the other side of the nose, which acts in concert by shunting blood out of its turbinates. This cycle occurs approximately every two and a half hours.
  • The olfactory segment is lined with a specialized type of pseudostratified columnar epithelium, known as olfactory epithelium, which contains receptors for the sense of the smell. This segment is located in and beneath the mucosa of the roof of each nasal cavity and the medial side of each middle turbinate. Histological sections appear yellowish-brown due to the presence of lipofuscin pigments. Olfactory mucosal cell types include bipolar neurons, supporting (sustentacular) cells, basal cells, and Bowman's glands. The axons of the bipolar neurons form the olfactory nerve (cranial nerve I) which enters the brain through the cribriform plate. Bowman's glands are serous glands in the lamina propria, whose secretions trap and dissolve odoriferous substances.

Blood supply

There is a rich blood supply to the nasal cavity. In some animals, such as dogs, the capillary beds flowing through the nasal cavity help cool the blood flow to the brain.

Blood supply comes from branches of both the internal and external carotid artery, including branches of the facial artery and maxillary artery. The named arteries of the nose are:

Nerve supply

Innervation of the nasal cavity responsible for the sense of smell is via the olfactory nerve, which sends microscopic fibers from the olfactory bulb through the cribriform plate to reach the top of the nasal cavity.

General sensory innervation is by branches of the trigeminal nerve (V1 & V2):

The nasal cavity is innervated by autonomic fibers. Sympathetic innervation to the blood vessels of the mucosa causes them to constrict, while the control of secretion by the mucous glands is carried on postganglionic parasympathetic nerve fibers originating from the facial nerve.

Function

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 nasal hair in the nostrils. 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.

Clinical significance

Diseases of the nasal cavity include viral, bacterial and fungal infections, nasal cavity tumors, both benign and much more often malignant, as well as inflammations of the nasal mucosa. Many problems can affect the nose, including:

See also

References

  1. ^ "nasal fossa". TheFreeDictionary.com.
  2. ^ Knipe, Henry. "Ostiomeatal complex | Radiology Reference Article | Radiopaedia.org". Radiopaedia.
  3. ^ Moore, Keith L; Dalley, Arthur F. (1999). Clinically Oriented Anatomy. Philadelphia: Lippincott Williams & Wilkins.

External links

  • lesson9 at The Anatomy Lesson by Wesley Norman (Georgetown University)
  • Gross anatomy dissection of the nasal cavity, video [1] and [2]
Acoustic rhinometry

Acoustic rhinometry is a diagnostic measurement of cross sectional area and length of the nose and the nasal cavity through acoustic reflections. It can be used to measure nasal anatomical landmarks, and nasal airway changes in response to allergen provocation tests. The size and the pattern of the reflected sound waves provide information on the structure and dimensions of the nasal cavity, with the time delay of reflections correlating with the distance from the nostril.

Brad Byers

Brad Byers (born October 8, 1959) is an American entertainer known for his extreme performances, including sword swallowing, lying on beds of nails and inserting various tools into his nasal cavity. For the latter he is also referred to as a "Human toolbox". He holds several World Records. His brother Rod assists him in some performances.

Esthesioneuroblastoma

Esthesioneuroblastoma, is a rare cancer of the nasal cavity. Arising from the upper nasal tract, esthesioneuroblastoma is believed to originate from sensory neuroepithelial cells, also known as neuroectodermal olfactory cells.Due to the location of the tumor and its proximity to the cranial cavity, esthesioneuroblastoma can be highly invasive and challenging to treat. There is no consensus on an appropriate treatment approach of esthesioneuroblastoma because of the rarity of the disease. Most studies reported cranial surgical resection with radiotherapy or chemotherapy to target the tumor.

Ethmoid bone

The ethmoid bone (; from Greek ethmos, "sieve") is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that make up the orbit of the eye.

Ethmoidal labyrinth

The ethmoidal labyrinth or lateral mass of the ethmoid bone consists of a number of thin-walled cellular cavities, the ethmoid air cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial plate forms part of the nasal cavity. In the disarticulated bone many of these cells are opened into, but when the bones are articulated, they are closed in at every part, except where they open into the nasal cavity.

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 early therapsids and mammals. Ridges in the nasal cavity of Glanosuchus suggest it had an at least partially endothermic metabolism similar to modern mammals.

Human nose

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 and the nasal cartilages, including the nasal septum which separates the nostrils and divides the nasal cavity into two. On average the nose of a male is larger than that of a female.

The main function of the nose is respiration, and the nasal mucosa lining the nasal cavity and the paranasal sinuses carries out the necessary conditioning of inhaled air by warming and moistening it. Nasal conchae, shell-like bones in the walls of the cavities, play a major part in this process. Filtering of the air by nasal hair in the nostrils prevents large particles from entering the lungs. Sneezing is a reflex to expel unwanted particles from the nose that irritate the mucosal lining. Sneezing can transmit infections, because aerosols are created in which the droplets can harbour pathogens.

Another major function of the nose is olfaction, the sense of smell. The area of olfactory epithelium, in the upper nasal cavity, contains specialised olfactory cells responsible for this function.

The nose is also involved in the function of speech. Nasal vowels and nasal consonants are produced in the process of nasalisation. The nasal cavity is the third most effective vocal resonator.

There are many plastic surgery procedures on the nose, known as rhinoplasties available to correct various structural defects or to change the shape of the nose. Defects may be congenital, result from nasal disorders or from trauma and these are carried out by reconstructive surgery. Procedures used to change a nose shape electively are carried out by cosmetic surgeries.

Nasal hair

Nasal hair or nose hair is the hair in the nose. Adult humans have hair in the interior nasal passage. Nasal hair functions include filtering foreign particles from entering the nasal cavity and collecting moisture. In support of the first function, the results of a 2010 study indicated that increased nasal hair density decreases development of asthma in those who have seasonal rhinitis, possibly due to an increased capacity of the faces to filter out pollen and other allergens.Nasal hair should not be confused with cilia of the nasal cavity, which are the microscopic cellular strands that, unlike macroscopic nasal hair, draw mucus up toward the pharynx via their coordinated, back-and-forth beating.

Nasolacrimal canal

The canal containing the nasolacrimal duct is called the nasolacrimal canal.

It is formed by indentations in the inferior nasal conchae, maxilla and lacrimal bone. The canal drains into the nasal cavity through the anterior portion of the inferior meatus, which is between the inferior concha and the floor of the nasal cavity.

Nasolacrimal duct

The nasolacrimal duct (also called the tear duct) carries tears from the lacrimal sac of the eye into the nasal cavity. The duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards. The opening of the nasolacrimal duct into the inferior nasal meatus of the nasal cavity is partially covered by a mucosal fold (valve of Hasner or plica lacrimalis). Excess tears flow through nasolacrimal duct which drains into the inferior nasal meatus.

This is the reason the nose starts to run when a person is crying or has watery eyes from an allergy, and why one can sometimes taste eye drops. For the same reason when applying some eye drops it is often advised to close the nasolacrimal duct by pressing it with a finger to prevent the medicine from escaping the eye and having unwanted side effects elsewhere in the body.

Like the lacrimal sac, the duct is lined by stratified columnar epithelium containing mucus-secreting goblet cells, and is surrounded by connective tissue.

Nasopalatine nerve

One branch of the pterygopalatine ganglion (trigeminal nerve, maxillary branch), longer and larger than the others, is named the nasopalatine nerve (sometimes called the long sphenopalatine nerve).

It enters the nasal cavity through the sphenopalatine foramen, passes across the roof of the nasal cavity below the orifice of the sphenoidal sinus to reach the septum, and then runs obliquely downward and forward between the periosteum and mucous membrane of the lower part of the septum.

It descends to the roof of the mouth through the incisive canal and communicates with the corresponding nerve of the opposite side and with the greater palatine nerve.

It supplies the palatal structures around the maxillary anterior teeth (central incisors, lateral incisors, and the canines).

It also furnishes a few filaments to the mucous membrane of the nasal septum.

The medial superior posterior nasal branches of the maxillary nerve usually branch from the nasopalatine nerve.

It was first discovered by Domenico Cotugno.

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 through the pharynx, shared with the digestive system, and then into the rest of the respiratory system. In humans, the nose is located centrally on the face and serves as an alternative respiratory passage especially during suckling for infants. On most other mammals, it is located on the upper tip of the snout.

Olfactory foramina

The olfactory foramina, also known as the cribriform foramina (cribr- is "a sieve" in Greek), is the grouping of holes located on the cribriform plate. The cribriform plate forms the roof of the nasal cavity, and the olfactory foramina are in the two depressions lateral to the median blade of the cribriform plate called the crista galli. There is a pair of olfactory bulbs of the brain that rest in these two depressions. These holes that make up the olfactory foramina allow passage for about 20 bundles of nerve fibers that make up the olfactory nerve, also known as Cranial Nerve I (CNI), from the nasal cavity to meet with the olfactory bulbs. Therefore, the olfactory foramina are necessary for the human sense of smell. These foramina vary in size and number with age.

Ophthalmic nerve

The ophthalmic nerve (first division of fifth cranial nerve, ophthalmic division of trigeminal nerve, first division of trigeminal nerve, CN V1, latin: nervus ophthalmicus) is the first branch of the trigeminal nerve. The ophthalmic nerve is a sensory nerve mostly carrying general somatic afferent fibers that transmit sensory information to the CNS from structures of the eyeball, the skin of the upper face and anterior scalp, the lining of the upper part of the nasal cavity and air cells, and the meninges of the anterior cranial fossa. Some of ophthalmic nerve branches also convey parasympathetic fibers.

Palate

The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior bony hard palate and the posterior fleshy soft palate (or velum).

Paranasal sinuses

Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoidal sinuses are behind the eyes. The sinuses are named for the facial bones in which they are located.

Sphenoidal conchae

The sphenoidal conchae (sphenoidal turbinated processes) are two thin, curved plates, situated at the anterior and lower part of the body of the sphenoid. An aperture of variable size exists in the anterior wall of each, and through this the sphenoidal sinus opens into the nasal cavity.Each is irregular in form, and tapers to a point behind, being broader and thinner in front.

Its upper surface is concave, and looks toward the cavity of the sinus; its under surface is convex, and forms part of the roof of the corresponding nasal cavity.

Each bone articulates in front with the ethmoid, laterally with the palatine; its pointed posterior extremity is placed above the vomer, and is received between the root of the pterygoid process laterally and the rostrum of the sphenoid medially.

A small portion of the sphenoidal concha sometimes enters into the formation of the medial wall of the orbit, between the lamina papyracea of the ethmoid in front, the orbital plate of the palatine below, and the frontal bone above.

Sphenopalatine foramen

The sphenopalatine foramen is a foramen in the skull that connects the nasal cavity with the pterygopalatine fossa.

Surface ectoderm

The surface ectoderm (or external ectoderm) forms the following structures:

Skin (only epidermis; dermis is derived from mesoderm) (along with glands, hair, and nails)

Epithelium of the mouth and nasal cavity and glands of the mouth and nasal cavity

Tooth enamel (as a side note, dentin and dental pulp are formed from ectomesenchyme which is derived from ectoderm (specifically neural crest cells and travels with mesenchmyal cells)

Epithelium of anterior pituitary

Lens, cornea, lacrimal gland, tarsal glands and the conjunctiva of the eye

Apical ectodermal ridge inducing development of the limb buds of the embryo.

Sensory receptors in epidermis

External nose
Nasal cavity
Paranasal sinuses
Naso-pharynx

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