DIAGRAM OF THE HUMAN NOSE

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The Nose


The Nose

The nose is the body's primary organ of smell and also functions as part of the body's respiratory system.

Air comes into the body through the nose. As it passes over the specialized cells of the olfactory system, the brain recognizes and identifies smells. Hairs in the nose clean the air of foreign particles. As air moves through the nasal passages, it is warmed and humidified before it goes into the lungs.

The most common medical condition related to the nose is nasal congestion. This can be caused by colds or flu, allergies, or environmental factors, resulting in inflammation of the nasal passages. The body's response to congestion is to convulsively expel air through the nose by a sneeze.

Nosebleeds, known medically as epistaxis, are a second common medical issue of the nose. As many as 60 percent of people report nosebleed experiences, with the highest rates found in children under 10 and adults over 50.

diagram-of-human-nose.

The Anatomy of the Nose


The Anatomy of the Nose

The nose is the part of the respiratory tract that sits front and center on your face. You use it to breathe air in and to stop and smell the roses. The nose’s exterior anatomy includes the nasal cavity, paranasal sinuses, nerves, blood supply, and lymphatics.

The external part of the nose includes the root (between the eyes), the dorsum that runs down the middle, and the apex at the tip of the nose. Two openings called nostrils (nares) allow air in. They’re divided by the nasal septum (dividing wall of cartilage and bone), and the parts that surround the nostrils are called the alae (ala singular).

The nose has a bony part that’s formed by the bony nasal septum, the nasal bones, and parts of the maxillae, palatine, and frontal bones. The cartilaginous part of the nose is formed by two lateral cartilages, two alar cartilages, and a septal cartilage.

The nasal cavity
The nares serve as the entryway to the nasal cavities, which open posteriorly into the nasopharynx via the choanae. The walls of the nasal cavity include the following features:

Roof: The roof is divided into three parts: frontonasal, ethmoidal, and sphenoidal. Each part corresponds to the underlying bone of the same name.

Floor: The floor consists of the palatine process of the maxilla and the horizontal plate of the palatine bone.

Medial wall: This wall is the nasal septum, which is formed by the perpendicular plate of the ethmoid bone, the vomer, cartilage, and the nasal crests of the maxillary and palatine bones.

Lateral wall: This wall is hallmarked by three nasal conchae (superior, middle, and inferior) that project inferiorly from the wall. They divide the nasal cavity into four passages that have openings to the paranasal sinuses:

The sphenoethmoid recess lies posterior to the superior concha and has the opening for the sphenoidal sinus.

The superior nasal meatus lies between the superior and middle conchae and has openings to the posterior ethmoidal sinuses.

The middle nasal meatus is longer and deeper than the superior nasal meatus. The frontal sinus communicates with the middle nasal meatus via the infundibulum, a passageway that opens into the semilunar hiatus (groove in the ethmoid bone). The maxillary sinus opens into the semilunar hiatus. An ethmoidal bulla (a round swelling formed by the middle ethmoidal cells, or air-filled cavities) is formed just above the semilunar hiatus. The middle and anterior ethmoidal sinuses drain into the middle nasal meatus.

The inferior nasal meatus is found below the inferior nasal concha. The nasolacrimal duct opens into this meatus.

The nasal cavity is lined with nasal mucosa, except for the nasal vestibule, which is lined with skin. The mucosa over the superior one-third of the nasal cavity is the olfactory area. Air is drawn past the specialized mucosal cells called the olfactory epithelium as air is sniffed though the nose. The olfactory epithelium contains receptors of olfactory neurons that detect smells. Olfactory neurons (from CN I) join together to form nerve bundles that run up through the cribiform plate of the ethmoid bone to the olfactory bulb. The olfactory tract transmits the sensory information about smell from

The paranasal sinuses
The paranasal sinuses are air-filled cavities in the frontal, ethmoid, maxilla, and sphenoid bones. They’re lined with a mucosal membrane and have small openings into the nasal cavity:

Maxillary sinus: This sinus is located in the body of the maxilla behind the cheek just above the roots of the premolar and molar teeth. It’s shaped like a pyramid. It opens into the nasal cavity via the semilunar hiatus.

Frontal sinuses: Found within the frontal bone, each of these sinuses is triangular in shape and runs above the medial end of the eyebrow and backward to the orbit. They open into the nasal cavity via the semilunar hiatus.

Sphenoid sinuses: These sinuses are found in the sphenoid bone. Each opens into the sphenoethmoid recess.

Ethmoid sinuses: The anterior, middle, and posterior ethmoid sinuses are located in the ethmoid bone between the nose and the eye. The anterior sinus opens into the nasal cavity by the infundibulum, the middle sinus opens into the ethmoidal bulla, and the posterior sinus opens into the superior meatus.

Nerves, blood vessels, and lymphatics of the nose
Nerve supply to the external nose is provided by the infratrochlear and external nasal branches of the ophthalmic nerve and the infraorbital branch of the maxillary nerve, both of which are part of the trigeminal nerve (CN V). The olfactory nerves (CN I) pass through the cribiform plate of the ethmoid bone. General sensory innervation of the nasal cavity and the paranasal sinuses is from the ophthalmic nerve (CN V1) and maxillary nerve (CN V2).

Blood is supplied to the external part of the nose by branches of the ophthalmic and maxillary arteries. The skin of the ala and septum are supplied by the facial artery. Blood is brought to the walls of the nasal cavity and sinuses by branches of the maxillary artery. The most important is the sphenopalatine artery, which anastomoses with a branch of the superior labial artery. Venous blood is returned from the nasal cavity by veins that accompany the arteries.

Lymph from the nasal cavity drains into the submandibular lymph nodes and vessels that drain into the upper deep cervical lymph nodes.

The Organ of Smell

The Organ of Smell
(The Human Nose)


1 the External Nose
—The external nose is pyramidal in form, and its upper angle or root is connected directly with the forehead; its free angle is termed the apex. The lateral surface ends below in a rounded eminence, the ala nasi.

2 Structure of The Human Nose.
—The frame-work of the external nose is composed of bones and cartilages; it is covered by the integument, and lined by mucous membrane.

3 The bony frame-work occupies the upper part of the organ; it consists of the nasal bones, and the frontal processes of the maxillæ.

4 The cartilaginous frame-work (cartilagines nasi) consists of five large pieces, viz., the cartilage of the septum, the two lateral and the two greater alar cartilages, and several smaller pieces, the lesser alar cartilages The various cartilages are connected to each other and to the bones by a tough fibrous membrane.

5 The cartilage of the septum (cartilago septi nasi) is somewhat quadrilateral in form, thicker at its margins than at its center, and completes the separation between the nasal cavities in front. Its anterior margin, thickest above, is connected with the nasal bones, and is continuous with the anterior margins of the lateral cartilages; below, it is connected to the medial crura of the greater alar cartilages by fibrous tissue. Its posterior margin is connected with the perpendicular plate of the ethmoid; its inferior margin with the vomer and the palatine processes of the maxillæ.
The septal cartilage does not reach as far as the lowest part of the nasal septum. This is formed by the medial crura of the greater alar cartilages and by the skin; it is freely movable, and hence is termed the septum mobile nasi.
7 The lateral cartilage is situated below the inferior margin of the nasal bone, and is flattened, and triangular in shape. Its anterior margin is thicker than the posterior, and is continuous above with the cartilage of the septum, but separated from it below by a narrow fissure; its superior margin is attached to the nasal bone and the frontal process of the maxilla; its inferior margin is connected by fibrous tissue with the greater alar cartilage.
The portion which forms the medial wall (crus mediale) is loosely connected with the corresponding portion of the opposite cartilage, the two forming, together with the thickened integument and subjacent tissue, the septum mobile nasi. The part which forms the lateral wall (crus laterale) is curved to correspond with the ala of the nose; it is oval and flattened, narrow behind, where it is connected with the frontal process of the maxilla by a tough fibrous membrane, in which are found three or four small cartilaginous plates, the lesser alar cartilages (cartilagines alares minores; sesamoid cartilages). Above, it is connected by fibrous tissue to the lateral cartilage and front part of the cartilage of the septum; below, it falls short of the margin of the naris, the ala being completed by fatty and fibrous tissue covered by skin. In front, the greater alar cartilages are separated by a notch which corresponds with the apex of the nose.




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FIG. 852 Diagram of The Human Nose– Cartilages of the nose. Side view.




FIG. 853 Diagram of The Human Nose– Cartilages of the nose, seen from below.




FIG. 854 Diagram of The Human Nose– Bones and cartilages of septum of nose. Right side.
The muscles acting on the external nose have been described in the section on Myology. 10
The integument of the dorsum and sides of the nose is thin, and loosely connected with the subjacent parts; but over the tip and alæ it is thicker and more firmly adherent, and is furnished with a large number of sebaceous follicles, the orifices of which are usually very distinct. 11
The arteries of the external nose are the alar and septal branches of the external maxillary, which supply the alæ and septum; the dorsum and sides being supplied from the dorsal nasal branch of the ophthalmic and the infraorbital branch of the internal maxillary. The veins end in the anterior facial and ophthalmic veins. 12
The nerves for the muscles of the nose are derived from the facial, while the skin receives branches from the infratrochlear and nasociliary branches of the ophthalmic, and from the infraorbital of the maxillary. 13
the Nasal Cavity
—The nasal chambers are situated one on either side of the median plane. They open in front through the nares, and communicate behind through the choanæ with the nasal part of the pharynx. The nares are somewhat pear-shaped apertures, each measuring about 2.5 cm. antero-posteriorly and 1.25 cm. transversely at its widest part. The choanæ are two oval openings each measuring 2.5 cm. in the vertical, and 1.25 cm. in the transverse direction in a well-developed adult skull.
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Inside the aperture of the nostril is a slight dilatation, the vestibule, bounded laterally by the ala and lateral crus of the greater alar cartilage, and medially by the medial crus of the same cartilage. It is lined by skin containing hairs and sebaceous glands, and extends as a small recess toward the apex of the nose. Each nasal cavity, above and behind the vestibule, is divided into two parts: an olfactory region, consisting of the superior nasal concha and the opposed part of the septum, and a respiratory region, which comprises the rest of the cavity. 16




FIG. 855 Diagram of The Human Nose– Lateral wall of nasal cavity.
Lateral Wall—On the lateral wall are the superior, middle, and inferior nasal conchæ, and below and lateral to each concha is the corresponding nasal passage or meatus. Above the superior concha is a narrow recess, the sphenoethmoidal recess, into which the sphenoidal sinus opens. The superior meatus is a short oblique passage extending about half-way along the upper border of the middle concha; the posterior ethmoidal cells open into the front part of this meatus. The middle meatus is below and lateral to the middle concha, and is continued anteriorly into a shallow depression, situated above the vestibule and named the atrium of the middle meatus. On raising or removing the middle concha the lateral wall of this meatus is fully displayed. On it is a rounded elevation, the bulla ethmoidalis, and below and in front of this is a curved cleft, the hiatus semilunaris. 17
The bulla ethmoidalis is caused by the bulging of the middle ethmoidal cells which open on or immediately above it, and the size of the bulla varies with that of its contained cells. 18




FIG. 856 Diagram of The Human Nose – Lateral wall of nasal cavity; the three nasal conchæ have been removed.
The hiatus semilunaris is bounded inferiorly by the sharp concave margin of the uncinate process of the ethmoid bone, and leads into a curved channel, the infundibulum, bounded above by the bulla ethmoidalis and below by the lateral surface of the uncinate process of the ethmoid. The anterior ethmoidal cells open into the front part of the infundibulum, and this in slightly over 50 per cent. of subjects is directly continuous with the frontonasal duct or passage leading from the frontal air sinus; but when the anterior end of the uncinate process fuses with the front part of the bulla, this continuity is interrupted and the frontonasal duct then opens directly into the anterior end of the middle meatus. 19
Below the bulla ethmoidalis, and partly hidden by the inferior end of the uncinate process, is the ostium maxillare, or opening from the maxillary sinus; in a frontal section this opening is seen to be placed near the roof of the sinus. An accessory opening from the sinus is frequently present below the posterior end of the middle nasal concha. The inferior meatus is below and lateral to the inferior nasal concha; the nasolacrimal duct opens into this meatus under cover of the anterior part of the inferior concha. 20
Medial Wall—The medial wall or septum is frequently more or less deflected from the median plane, thus lessening the size of one nasal cavity and increasing that of the other; ridges or spurs of bone growing into one or other cavity from the septum are also sometimes present. Immediately over the incisive canal at the lower edge of the cartilage of the septum a depression, the nasopalatine recess, is seen. In the septum close to this recess a minute orifice may be discerned; it leads backward into a blind pouch, the rudimentary vomeronasal organ of Jacobson, which is supported by a strip of cartilage, the vomeronasal cartilage. This organ is well-developed in many of the lower animals, where it apparently plays a part in the sense of smell, since it is supplied by twigs of the olfactory nerve and lined by epithelium similar to that in the olfactory region of the nose. 21
The roof of the nasal cavity is narrow from side to side, except at its posterior part, and may be divided, from behind forward, into sphenoidal, ethmoidal, and frontonasal parts, after the bones which form it. 22
The floor is concave from side to side and almost horizontal antero-posteriorly; its anterior three-fourths are formed by the palatine process of the maxilla, its posterior fourth by the horizontal process of the palatine bone. In its anteromedial part, directly over the incisive foramen, a small depression, the nasopalatine recess, is sometimes seen; it points downward and forward and occupies the position of a canal which connected the nasal with the buccal cavity in early fetal life. 23
The Mucous Membrane—The nasal mucous membrane lines the nasal cavities, and is intimately adherent to the periosteum or perichondrium. It is continuous with the skin through the nares, and with the mucous membrane of the nasal part of the pharynx through the choanæ. From the nasal cavity its continuity with the conjunctiva may be traced, through the nasolacrimal and lacrimal ducts; and with the frontal, ethmoidal, sphenoidal, and maxillary sinuses, through the several openings in the meatuses. The mucous membrane is thickest, and most vascular, over the nasal conchæ. It is also thick over the septum; but it is very thin in the meatuses on the floor of the nasal cavities, and in the various sinuses. 24
Owing to the thickness of the greater part of this membrane, the nasal cavities are much narrower, and the middle and inferior nasal conchæ appear larger and more prominent than in the skeleton; also the various apertures communicating with the meatuses are considerably narrowed. 25
Structure of the Mucous Membrane
—The epithelium covering the mucous membrane differs in its character according to the functions of the part of the nose in which it is found. In the respiratory region it is columnar and ciliated. Interspersed among the columnar cells are goblet or mucin cells, while between their bases are found smaller pyramidal cells. Beneath the epithelium and its basement membrane is a fibrous layer infiltrated with lymph corpuscles, so as to form in many parts a diffuse adenoid tissue, and under this a nearly continuous layer of small and larger glands, some mucous and some serous, the ducts of which open upon the surface. In the olfactory region the mucous membrane is yellowish in color and the epithelial cells are columnar and non-ciliated; they are of two kinds, supporting cells and olfactory cells. The supporting cells contain oval nuclei, which are situated in the deeper parts of the cells and constitute the zone of oval nuclei; the superficial part of each cell is columnar, and contains granules of yellow pigment, while its deep part is prolonged as a delicate process which ramifies and communicates with similar processes from neighboring cells, so as to form a net-work in the mucous membrane. Lying between the deep processes of the supporting cells are a number of bipolar nerve cells, the olfactory cells, each consisting of a small amount of granular protoplasm with a large spherical nucleus, and possessing two processes—a superficial one which runs between the columnar epithelial cells, and projects on the surface of the mucous membrane as a fine, hair-like process, the olfactory hair; the other or deep process runs inward, is frequently beaded, and is continued as the axon of an olfactory nerve fiber. Beneath the epithelium, and extending through the thickness of the mucous membrane, is a layer of tubular, often branched, glands, the glands of Bowman, identical in structure with serous glands. The epithelial cells of the nose, fauces and respiratory passages play an important role in the maintenance of an equable temperature, by the moisture with which they keep the surface always slightly lubricated.
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Vessels and Nerves.
—The arteries of the nasal cavities are the anterior and posterior ethmoidal branches of the ophthalmic, which supply the ethmoidal cells, frontal sinuses, and roof of the nose; the sphenopalatine branch which supplies the mucous membrane covering the conchæ, the meatuses and septum, the septal branch of the superior labial of the external maxillary; the infraorbital and alveolar branches of the internal maxillary, which supply the lining membrane of the maxillary sinus; and the pharyngeal branch of the same artery, distributed to the sphenoidal sinus. The ramifications of these vessels form a close plexiform net-work, beneath and in the substance of the mucous membrane.
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FIG. 857 Diagram of the Human Nose– Section of the olfactory mucous membrane.

The veins form a close cavernous plexus beneath the mucous membrane. Some of the veins open into the sphenopalatine vein; others join the anterior facial vein; some accompany the ethmoidal arteries, and end in the ophthalmic veins; and, lastly, a few communicate with the veins on the orbital surface of the frontal lobe of the brain, through the foramina in the cribriform plate of the ethmoid bone; when the foramen cecum is patent it transmits a vein to the superior sagittal sinus.
29 The nerves of ordinary sensation are: the nasociliary branch of the ophthalmic, filaments from the anterior alveolar branch of the maxillary, the nerve of the pterygoid canal, the nasopalatine, the anterior palatine, and nasal branches of the sphenopalatine ganglion.
30 The nasociliary branch of the ophthalmic distributes filaments to the forepart of the septum and lateral wall of the nasal cavity. Filaments from the anterior alveolar nerve supply the inferior meatus and inferior concha. The nerve of the pterygoid canal supplies the upper and back part of the septum, and superior concha; and the upper nasal branches from the sphenopalatine ganglion have a similar distribution. The nasopalatine nerve supplies the middle of the septum. The anterior palatine nerve supplies the lower nasal branches to the middle and inferior conchæ.
31 The olfactory, the special nerve of the sense of smell, is distributed to the olfactory region. Its fibers arise from the bipolar olfactory cells and are destitute of medullary sheaths. 


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FIG. 858– Diagram of The Human Nose-Nerves of septum of nose. Right side
The Accessory Sinuses of the Nose 33
The accessory sinuses or air cells of the nose are the frontal, ethmoidal, sphenoidal, and maxillary; they vary in size and form in different individuals, and are lined by ciliated mucous membrane directly continuous with that of the nasal cavities. 34
The Frontal Sinuses (sinus frontales), situated behind the superciliary arches, are rarely symmetrical, and the septum between them frequently deviates to one or other side of the middle line. Their average measurements are as follows: height, 3 cm.; breadth, 2.5 cm.; depth from before backward, 2.5 cm. Each opens into the anterior part of the corresponding middle meatus of the nose through the frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid. Absent at birth, they are generally fairly well developed between the seventh and eighth years, but only reach their full size after puberty. 35




FIG. 859– Diagram of the Human Nose -Coronal section of nasal cavities.
The Ethmoidal Air Cells consist of numerous thin-walled cavities situated in the ethmoidal labyrinth and completed by the frontal, maxilla, lacrimal, sphenoidal, and palatine. They lie between the upper parts of the nasal cavities and the orbits, and are separated from these cavities by thin bony laminæ. On either side they are arranged in three groups, anterior, middle, and posterior. The anterior and middle groups open into the middle meatus of the nose, the former by way of the infundibulum, the latter on or above the bulla ethmoidalis. The posterior cells open into the superior meatus under cover of the superior nasal concha; sometimes one or more opens into the sphenoidal sinus. The ethmoidal cells begin to develop during fetal life. 36
The Sphenoidal Sinuses contained within the body of the sphenoid vary in size and shape; owing to the lateral displacement of the intervening septum they are rarely symmetrical. The following are their average measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior depth, 2.2 cm. When exceptionally large they may extend into the roots of the pterygoid processes or great wings, and may invade the basilar part of the occipital bone. Each sinus communicates with the sphenoethmoidal recess by means of an aperture in the upper part of its anterior wall. They are present as minute cavities at birth, but their main development takes place after puberty. 37


Diagram of The Human Nose

FIG. 860– —Specimen from a child eight days old. By sagittal sections removing the lateral portion of frontal bone, lamina papyracea of ethmoid, and lateral portion of maxilla—the sinus maxillaris, cellulæ ethmoidales, anterior and posterior, infundibulum ethmoidale, and the primitive sinus frontalis are brought into view.


Diagram of The Human Nose

FIG. 861– Specimen from a child one year, four months, and seven days old. Lateral view of frontal, ethmoidal, and maxillary sinus areas. (Davis.)
The Maxillary Sinus the largest of the accessory sinuses of the nose, is a pyramidal cavity in the body of the maxilla. Its base is formed by the lateral wall of the nasal cavity, and its apex extends into the zygomatic process. Its roof or orbital wall is frequently ridged by the infra-orbital canal, while its floor is formed by the alveolar process and is usually 1/2 to 10 mm. below the level of the floor of the nose; projecting into the floor are several conical elevations corresponding with the roots of the first and second molar teeth, and in some cases the floor is perforated by one or more of these roots. The size of the sinus varies in different skulls, and even on the two sides of the same skull. The adult capacity varies from 9.5 c.c. to 20 c.c., average about 14.75 c.c. The following measurements are those of an average-sized sinus: vertical height opposite the first molar tooth, 3.75 cm.; transverse breadth, 2.5 cm.; antero-posterior depth, 3 cm. In the antero-superior part of its base is an opening through which it communicates with the lower part of the hiatus semilunaris; a second orifice is frequently seen in, or immediately behind, the hiatus. The maxillary sinus appears as a shallow groove on the medial surface of the bone about the fourth month of fetal life, but does not reach its full size until after the second dentition. At birth it measures about 7 mm. in the dorso-ventral direction and at twenty months about 20 mm. 38


Diagram of The Human Nose

FIG. 862– Specimen from a child eight years, eight months, and one day old. Lateral view of frontal, ethmoidal and maxillary sinus areas, the lateral portion of each having been removed by sagittal cuts. Note that the sinus frontalis developed directly from the infundibulum ethmoidale. Note also the incomplete septa in the sinus maxillaris.
Diagram of The Human Nose

What diseases or disorders can the nose have?

What diseases or disorders can the nose have?

One disored that your nose may have is a deviated septum- this is where the bone that splits your nostrils is skew; either because it grew that way or you broke your nose. This can create a blockage in your nose, making it difficult to breath.
Another disored is small nostrils; this also makes it difficult to breathe and can be a cause of snoring. It is also a sign of cancer so see you docter straight away before its to late.
Diagram of the human Nose.

Physiology of the Human Nose

Physiology of the Human Nose



The human nose has several physiologic functions. As the air is inspired through the nose it is humidified and warmed by passing over the moist and warm nasal mucosa. The nose is an energy-conscious organ in that expired air is cooled and some of the moisture is recaptured. The functions of warming and humidification require a tremendous blood flow to the nasal mucosa and also place substantial stress on the nasal mucosa. The nose has what is known as a nasal cycle. 
To allow the mucosa time to rest from these functions, the nose has periods in which one side of the nose becomes swollen, which we call congestion. During the same period the other side of the nose remains patent or decongested. The normal nasal cycle lasts from three to six hours, and during this time first one side of the human nose will be congested and the other side will be patent; then the second side becomes congested as the first side becomes patent. It is also normal for the human nose to be congested when an individual lies down.
Particularly if you lie on your side you may notice that the downside of your nose becomes congested. Olfaction is the medical word for smell. Smell is one of the six human senses and for some individuals is a very important sense; for others it seems to be less important. The olfactory centers, as described under the anatomy section, reside very high along the roof of the nose. In order for these centers to be stimulated, the odors have to be inspired into the human nose and carried up to the roof of the human nose. If the odor does not reach the roof of the nose due to a variety of conditions, the odor will not be perceived. The nose is capable of distinguishing a large number of different odors. Our understanding of precisely how this occurs is limited, but increasing.

Taste is a sense very different from olfaction. It is another of the human senses and is perceived primarily on the tongue. There are four recognized tastes and these are sweet, salty, sour, and bitter. They occupy geographically separate areas on the tongue and are perceived in cells clustered together in taste buds. The sense of smell plays a major role in the flavor of foods and it is common for individuals who lose their sense of smell to report that food loses its taste. This is of course incorrect; the food has only lost its aroma, and taste (sweet, salty, sour, bitter) remains intact.

How does the human nose work?

How does the human nose work?

The nose works with the olfactory system. This is a series of nerve endings that are located in the nasal passage. It allows people to pick up scents. People with a cold often can't smell things because their nose is blocked.
Diagram of the Human Nose

The Human Nose

The Human Nose

Diagram of the Human Nose
The external human nose, composed of bone and cartilage, is the most prominent feature of the face in humans. The internal human nose is a hollow structure above the roof of the mouth, divided by the septum into two nasal cavities that extend from the nostrils to the pharynx. The mucous membrane that lines the nasal cavities is covered with fine hairs known as cilia that help to filter dust and impurities from the air before it reaches the lungs; the air is also moistened as it passes over the sticky nasal membrane. In the human nose, there are three horizontal folds on the walls of the nasal cavities, called the conchae: other mammals may have more conchae. The uppermost concha is densely supplied with capillaries that warm the air passing over them to near body temperature. High in the nasal cavity is a small tract of mucous membrane containing the nerve cell endings of the olfactory nerve, which impart the sense of smell. Therefore, inflammation of the nasal mucous membranes, which commonly accompanies colds and other infections, not only obstructs breathing but also impairs the sense of smell.
Diagram of the human nose...