Nasal cavity

The nasal cavities or nasal fossae are two spaces filled of air above and behind of the Nez, in the middle of the face.

The nasal fossae are important to heat and cleanse the inhaled air. Moreover, they contain the bodies implied in the Olfaction.

Limits

The nasal fossae are limited:

by the pyriforme opening ahead
by the opening choale behind
by the nasal Os and the ethmoïde in top
by the Jawbone, the ethmoïde and the lower nasal Cornet laterally
the Palais (Palatine jawbone and ) separates the nasal fossae from the oral Cavité
the nasal fossae are separate médialement by a vertical partition, the nasal Septum consisted the vomer and the ethmoïde.

The nasal fossae are prolonged ahead by the nose, and behind by the Pharynx.

The sine paranasaux are connected to the nasal fossae by small openings called ostia.

Vascularization and innervation

Vascularization is rich; in certain animals like the Dog S, the capillary bed passing by the nasal fossae helps to cool cerebral blood circulation. Vascularization is ensured by several sources, on the one hand the branches of the external carotid like the Artère sphénopalatine; in addition branches of the internal carotid like the former and posterior arteries ethmoidales which present anatomoses with the external network carotidien.

The innervation is made primarily via the facial Nerf.

Functions

On the lateral sides there are three horns which offer a resistance to the air flow and direct it towards the olfactive epithelium in top.

The horns play an important role in the respiratory process. An excessive résection of horns (Turbinectomie) can lead to the Syndrome of the nose empties (SNV), also known under the name of Empty Nose Syndrome (ENS). The Body voméronasal, located behind on the septum, has a role in the detection of Phéromones.

The cells ciliées and the Mucus on the walls eliminate from the circulating air dust and the germs. The lashes push back mucus towards the pharynx, where it will be swallowed.

Role of the horns in the respiratory system

The horns are a superposition of long, narrow and curved bones (in the shape of stretched shell), covered with a thick layer with fabric, very vascularized, érectile and glandular.

They are placed laterally in the nasal cavities and are rolled up way médiale and downwards inside the nasal respiratory tracts.

There exist 3 pairs of horns. A pair of horns has a horn in each of the 2 nasal cavities. The two nasal cavities are separated by the nasal partition called septum.

That means that there are 3 horns in each nasal cavity:

the lower horn: largest, as long as an index of the finger;
the average horn: as long as auricular;
the higher horn: very small.

The horns maintain largest of functional breathing as well as mucous fabric of the nose.

They have a very rich network of blood and nervous provisioning which gives them considerable capacities of erection (very similar to the penis), of turgescence and clearing, in response to the climatic conditions and the needs unceasingly fluctuating for the body.

For example, if a person must suddenly start to run to avoid a danger, the horns automatically will narrow, thus allowing a greater absorption of air each inspiration.

On another side, if a person tries to rest in a cold and dry environment, the horns will inflate in order to provide a mucous surface of more important exposure to the air, guaranteeing thus that all the air aspired by the nose crosses these fabrics and sufficiently is heated (body adjustment at the temperature), is humidified (up to 98%) and is filtered.

Filtering is ensured by a thin layer called “alveolar epithelium” which recovers the fabric érectile horns, itself called “endothéliale layer” or “lamina propria”.

This layer is made cells with goblet which secrete mucus intended to cover the nasal cavities and transport the lymphatic serum containing of the anti-bacterial and antiviral agents and playing an important role in the first respiratory line of defense of the body.

All the airborne particles of more than 2 to 3 Micromètre S remain imprisoned in mucus and are neutralized by the lymphatic serum. The whole of produced mucus as well as waste are periodically propelled towards the back of the nose until they are swallowed by the throat on the level of the nasopharynx.

Mucus is involved towards the throat by the roadbase of the alveolar epithelium, furnished with lashes.

This ciliaire layer is similar to a carpet of million microscopic lashes which trap the air irritants and propel them towards the Nasopharynx the made-to-order of the movement of a wave.

If mucus is sufficiently diluted and that the nose is not too dry, one will not even feel that one is, in fact, swallowing mucus in a permanent way. A person in good health swallows on average 0,65 liter of mucus by 12 midnight.

If the lashes are damaged or paralyzed, as during a nasal infection engraves, mucus accumulates in the nose and the throat and becomes thick and yellowish. In the severe cases of dryness, mucus dries in the nose and forms painful crusts.

The horns divide the nasal respiratory tracts into 3 air passages similar to furrows, the meatuses inferior, means and superior, thus forcing the air to run out according to a model constant and balanced around more possible large surface of lashes and fabric.

The horns are primarily the radiator and the engine of the nose.

Without them, the flow of air would be turbulent (causing a known nasal obstruction under the name of “paradoxical obstruction”), would not meet a sufficient quantity of mucous fabric and thus would not be cleaned, is heated and is not humidified. This means that the throat and the lungs would be submerged of dirty air, cold and dry.

The horns are also rich nervous receivers sensitive to air flow (related to the “trigéminé” nervous circuit, the fifth cranial nerve).

These receivers detect the pressure and the temperature and helps thus, by a still unknown mechanism, with the activation of the receivers of odors located in the higher areas of the nose.

The lower horns are largest of the horns and are the principal humidifying fabrics, heating, filter and orientators of air flow.

The major part of the flow of air inhaled voyage in the average meatus, between the lower horns and the average horns.

The average horns are smaller and are projected downwards starting from the sines ethmoïdes. They shelter the openings to the jawbones and to the sines ethmoïdes and act as of the plugs of air so that the sines are not in direct contact with the flow of nasal pressurized air.

The higher horns protect the olfactive Bulbe and are also innervés with a multitude of olfactive nervous terminations which are prolonged some share in the average horns.

Diseases

Viral infections , Cancer, Herpes, with mucous obstruction

Internal bonds

External bond

Simple: Nasal cavity

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