Nose

Generality

The nose is the prominence located at the center of the face, between the two eyes and the two cheeks, which provides the sense of smell and represents the main entry of the respiratory tract.

Its structure is quite complex and includes elements of bone and cartilage, blood vessels, lymphatic vessels and important nerve endings.

Externally, the nose has a characteristic pyramid shape, in which it is possible to recognize at least 5 anatomical reference areas: the nasal root, the nasal bridge, the nasal back, the two nasal wings and the nasal tip.

Internally, the nose corresponds to the two nasal cavities; the latter are two empty spaces deriving from the particular conformation of some bones of the skull (including the ethmoid bone, the vomer, the palatine bones and the maxillary bones).

The influx of oxygenated blood to the nose is mainly due to some branches and sub-branches of the internal carotid arteries and external carotid arteries.

What is the nose?

The nose is the prominence located at the center of the face, partly between the two eyes and partly between the two cheeks.

Equipped with two outward openings - the so-called nostrils - the nose is the organ of smell and the main entry of the respiratory tract (the secondary entrance is the mouth).

Anatomy

The nose is a very complex structure, which includes elements of bone and cartilage, blood vessels, lymphatic vessels and nerve endings.

In general, to simplify the description of the nose, the anatomists analyze the external part of the latter separately from the inner part.

Better known as an external nose or nasal pyramid, the outer part is the portion of the nose visible to the naked eye, which distinguishes each face and has a characteristic pyramid shape.

The inner part (or inner nose ), on the other hand, is the portion of the nose that coincides with the two nasal cavities and in which the olfactory cells (ie the cells that guarantee the sense of smell) and the structures for the passage of inhaled air reside, during breathing.

EXTERNAL NOSE

In the external nose, 5 anatomical reference areas can be recognized, which are: the nasal root, the nasal bridge, the nasal back, the two nasal wings and the nasal tip .

Nasal root: identifiable where the frontal suture resides, it represents the upper portion of the external nose. It is in continuity with the forehead.
Nasal bridge: it is the saddle-shaped portion of a horse usually located between the two eyes.
Separate the nasal root from the nasal back.
Nasal back: also known as nasal crest, it is the prominent tract that goes from the nasal bridge to the nasal tip and that distinguishes the shape of the nose.
It is the portion of the nose that stands out in the eyes in the profile view.
Nasal wings: these are the portions of the outer nose that are lateral to the nasal back and the nasal tip. Surround the nostrils.
Nasal tip: also known as nasal apex, is the lower portion of the external nose.
In fact, it marks the end of the nasal spine.
Below, it has two distinct openings, better known as nasal nostrils, which represent the beginning of the two nasal cavities (and of the internal nose).

The skeleton of the external nose comprises elements of bony nature and elements of cartilaginous nature.

The elements of bone nature are: the two nasal bones, the two maxillary bones and the frontal bone .

The elements of cartilaginous nature, on the other hand, are: the two upper lateral cartilages, the two greater alar cartilages ( or lower lateral cartilages ) , the two lower wing cartilages, the septal cartilage and the so-called columella .

Nasal bones. They form the nasal bridge and the upper part of the nasal spine. Each nasal bone borders: superiorly, with the frontal bone; laterally, with the homolateral maxillary bone; finally, medially, with the contralateral nasal bone.
They are cranial bones of the so-called splancnocranium (see the article on the skull).
Maxillary bones. They support the lateral part of the nose and articulate with numerous bones of the inner nose. Belonging to the splanchocranium, they are the bones of the jaw.
Frontal bone. It constitutes a good part of the nasal root. It is bordered on the lower side by the two nasal bones. Belonging to the neurocranium, it is the unequal cranial bone of the forehead.

Figure : the bones of the skull. Thanks to the image, readers can identify the location of some of the cranial bones that participate in the formation of the nose (eg: nasal bones, vomer, maxillary bones, ethmoid bone, etc.).

Figure : the cartilages of the external nose.

Of all, we note in particular the columella . The latter resides in the lower part of the nasal tip and is the strip of cartilaginous tissue, which separates the right nostril from the left nostril.

The external lining of the nose is particular. In fact, while the skin covering the bones is thin and devoid of any type of gland, the skin that covers the various cartilaginous structures is thick and rich in sebaceous glands .

The cutaneous lining of the external nose reaches the outer edges of the nasal nostrils; after that, the mucosa begins.

INTERNAL NOSE

In the two nasal cavities of the inner nose, the experts recognize three anatomical reference regions, which are: the vestibule, the olfactory region and the respiratory region .

Vestibule: considering the nostrils as the beginning of the internal nose, it is the very first part of the nasal cavities. It is an enlarged area, provided with a characteristic mucous coating.
In adults, it is also the region of the inner nose from which nasal hairs can originate.
Olfactory region: located at the apex of the nasal cavities, it is the region of the internal nose in which the olfactory cells reside, ie the cells that guarantee the perception of odors.
Respiratory region: it is the largest region of the internal nose. It is covered by a ciliate pseudostratified epithelium, in which also goblet muciparous cells reside. Goblet mucipar cells are cellular elements that secrete mucus.

Various skull bones and osteo-cartilaginous components contribute to the particular structure of the inner nose (and of the two nasal cavities). Among the bones, we note: the palatine bones, the ethmoid bone, the inferior turbinates, the vomer and the aforementioned maxillary bones ; among the osteo-cartilaginous components, on the other hand, the nasal septum, that is the lamina which, interposed between the two nasal cavities, separates them hermetically deserves a particular mention.

Palatine bones: they are the two bony elements that form the latero-inferior margin of the nasal cavities, the floors of the orbital cavities and the roof of a part of the hard palate. L-shaped, they articulate each other and with different bones of the skull, including: the ethmoid bone, the maxillary bones, the inferior turbinates and the vomer.
Ethmoid bone: it is an uneven bone important for the anatomy of the internal nose, as it gives rise, in each nasal cavity, to three very particular structures, called lamina cribrosa, superior turbinate and middle turbinate .
The lamina cribrosa is a sort of plate with small holes, through which pass the nerve fibers of the olfactory nerve .
The upper and middle turbinates, on the other hand, are in fact small bony protrusions, covered by erectile-cavernous vascular tissue (more internally) and by larynx respiratory mucosa (more externally). As can be guessed, the upper turbinate is so called because it dominates the middle turbinate.
Lower turbines: one located in the right nasal cavity and one in the left nasal cavity, are two protrusions similar to the turbinates of the ethmoid bone. The similarity with the latter also concerns the coverings they are supplied with.
From the standpoint of position, the inferior turbinates reside below the upper turbinates and the average turbinates.
Vomere: it is the uneven bone that constitutes the lower part of the nasal septum. Similar to the ploughshare used by farmers, the ploughshare of the skull articulates with the palatine bones and the maxillary bones, below, and the ethmoid bone, anteriorly.

Inside the nasal cavities, the so-called paranasal sinuses find an outlet through the orifices called osti . Paranasal sinuses are natural cavities filled with air, which are located in the thickness of the bones of the face placed around the eyes, nose and cheeks (ethmoid bone, sphenoid bone, frontal bone and maxillary bones). The paranasal sinuses are, in all, 4 pairs : the two frontal sinuses, the two ethmoid sinuses, the two sphenoid sinuses and the two maxillary sinuses .

Their functions are varied: they are essential for the functionality and protection of the respiratory system, increase the perception of odors, lighten the skull, regulate the tone of the voice and promote the drainage of tears and any mucous secretions in the direction of the cavities nasal.

Later, the nasal cavities communicate with the mouth, through two openings that take the name of coane .

Very often, anatomy books describe the nasal cavities as those empty spaces ranging from the vestibule to the nasopharynx .

Also known as nasopharynx, the nasopharynx is the upper part of the pharynx, placed in direct contact with the choanae, or the two posterior openings of the nasal cavities.

Figure : nasal cavities. The image shows the anatomical regions of reference of the internal nose (they are indicated with different colors), the turbinates, the nasopharynx and some of the paranasal sinuses.

MUSCLES

The nose includes several muscles, which have the task of controlling their movements.

Innervated by the facial nerve ( VII cranial nerve ), these muscles are: the procero muscle, the levator muscle of the upper lip and the wing of the nose, the nasal muscle, the depressor muscle of the nasal septum, the anterior dilator muscle of the nostrils and the posterior dilatator muscle of the nostrils .

Procerus muscle: resides above the nasal bones and above part of the upper lateral cartilages. Its contraction determines the frowning of the eyebrows and the formation of wrinkles at the level of the nasal bridge.
Elevating muscle of the upper lip and wing of the nose: even muscle element, takes place laterally to the ipsilateral nasal nostril and above the homolateral maxillary bone. It helps dilate the nasal nostril, lift the upper lip and elevate the nasal wing.
Nasal muscle: it is an even muscle element, which resides in a lateral position, about halfway down the nose. It consists of two parts, which are called transverse part and wing part .
The transverse part of the nasal muscle forces (ie closes) the nasal nostrils; the wing part, instead, dilates the nasal wings.
Depressor muscle of the nasal septum: it is an even muscle element, which arises at the level of the incisive fossa of the maxillary bone and ends its path at the level of the nasal septum.
From the functional point of view, it assists the wing part of the nasal muscle in its action of dilation of the nasal wings.
Anterior dilator muscle of the nostrils and posterior dilator muscle of the nostrils: they are two even muscle elements, which reside on the sides of the nose, approximately where there are the major and minor alar cartilages.
As can easily be guessed from their name, the anterior dilator muscle of the nostrils and the posterior dilator muscle of the nostrils serve for the dilation of the nasal nostrils.

VASCULARIZATION OF THE EXTERNAL NOSE

To supply oxygenated blood to the skin of the external nose are, mainly, the branches of the maxillary artery and the ophthalmic artery and, secondarily, the angular artery and the lateral nasal artery . The maxillary artery derives from the external carotid artery ; the ophthalmic artery from the internal carotid artery ; finally, the angular artery and the lateral nasal artery from the facial artery.

The drainage of venous blood belongs to a series of vessels that end in the so-called facial vein, which, in turn, flows into the internal jugular vein .

As far as the lymphatic drainage of the external nose is concerned, this is due to a network of superficial lymphatic vessels that accompany the facial vein very closely. Like all the lymphatic vessels of the head and neck, the lymphatic vessels of the external nose drain their contents into the deep cervical lymph nodes .

VASCULARIZATION OF THE INTERNAL NOSE

Thanks to a large network of arterial blood vessels, the blood supply to the internal nose is considerable. This high blood supply is essential for the warming action of the air inspired by breathing.

To supply oxygenated blood the inner nose are:

The anterior ethmoid artery and the posterior ethmoid artery. These are two branches of the ophthalmic artery, which is, in turn, a branch of the internal carotid artery.
The sphenopalatine artery, the major palatine artery, the superior labial artery and the lateral nasal arteries . All these arteries derive directly from the external carotid artery.

In essence, therefore, the blood supply to the internal nose is due to branches or sub-branches of the internal carotid arteries and of the external carotid arteries.

As far as the drainage of venous blood is concerned, this important action involves veins that follow the same path of the aforementioned arteries and that pour their contents into the pterygoid plexus, the facial vein, the cavernous sinus and the sagittal sinus .

INNERVATION OF THE EXTERNAL NOSE

The sensory innervation of the external nose is due to some sub-branches of the trigeminal nerve, which is the fifth cranial nerve .

Going into more detail:

The cutaneous sensitivity of the nasal back and of the nasal wings belongs to the so-called external nasal nerve . The external nasal nerve is a branch of the ophthalmic nerve, which is, in turn, one of the three main branches of the trigeminal nerve (the other two being the maxillary nerve and the mandibular nerve ).
The cutaneous sensitivity of the lateral portions of the external nose (excluding nasal wings) belongs to the so-called infraorbital nerve, which is a branch of the maxillary nerve.

As already stated, the motor innervation of the external nose (thus the innervation of the muscles of the external nose) is under the control of the facial nerve.

INNOVATION OF THE INTERNAL NOSE

Experts distinguish the sensory innervation of the internal nose in two different types: the special type sensitive innervation and the general type sensitive innervation .

The special sensitive innervation (or special sensory innervation) consists of the network of nerve endings, which provide the sense of smell. Specifically, these are the nerve fibers of the olfactory nerves, which range from the olfactory cells of the olfactory region of the nose to the olfactory bulb of the brain, passing through the holes of the cribrosa lamina of the ethmoid bone.

The general sensory innervation, on the other hand, consists of the network of nerve endings, which control the internal sensitivity of the nasal cavities, including the vestibule. To deal with it are:

The ophthalmic nerve (main branch of the trigeminal nerve), which innervates the vestibule;
The nasopalatine nerve and the nasociliary nerve (respectively, branch of the maxillary nerve and branch of the ophthalmic nerve), which innervate the nasal septum and the lateral walls of the nasal cavities.

Development

In humans, the nose begins to form from the 4th week of gestation : the embryonic portion from which it derives is the so-called neural crest .

Initially, the nose is one with the mouth; then, as the pregnancy progresses, the nose and mouth separate, distinguishing one from the other.

The muscles, the cartilages and the bones, of which we have spoken previously, begin to form and take on the final appearance around the 10th week of intrauterine life . It is at this stage of pregnancy that doctors can identify nasal malformations by means of prenatal ultrasound scans.

Function

The olfactory cells, present in the olfactory region of the inner nose, are provided with specific structures, called olfactory receptors .

Olfactory receptors are the true creators of the sense of smell. In fact, through them the olfactory cells capture the smells and stimulate the nerve fibers of the connected olfactory nerves (NB: as you will remember the olfactory cells are connected to the nerve fibers of the olfactory nerves).

With the stimulation of the olfactory nerves, the brain - to be precise the olfactory bulbs of the brain - receives information on the odors present in the environment and processes, if necessary, the most appropriate answers.

ROLE OF THE NOSE INSIDE THE RESPIRATORY PROCESS

As the first part of the airway, the nose has the task of adapting the inspired air to the needs of the human body. For this reason, it is provided with structures (eg: turbinates or the dense network of blood vessels) which allow it to heat, humidify and purify the air introduced with the respiratory acts.

If the nasal cavities lacked the turbinates and their other characteristic structures, the human being would introduce into the lungs air not sufficiently hot, not purified from germs and not properly humidified.

diseases

The nose may be the victim of: fractures of some of its bony parts, deformations of some of its osteo-cartilaginous components or other morbid conditions, including for example turbinate hypertrophy .

Furthermore, the nose may be the site of well-known and common clinical manifestations, such as nose bleeds (or epistaxis ), the so-called runny nose (or rhinorrhea ) or a stuffy nose .

FRACTURES FOR THE NOSE

Fractures of one or more bone components of the nose are almost always injuries of traumatic origin .

The most important types of fractures to the nose are the fracture of one or both nasal bones and the fracture of the lamina cribrosa .

Nasal bone fractures are fairly common conditions, which rarely involve complications and necessitate surgery. The typical symptoms are: pain, local swelling, haematomas on the nose and under the eyes, loss of blood from the nose, respiratory problems and more or less marked anatomical deformities.

As for the fractures of the lamina cribrosa, these are fortunately unusual conditions, which can have serious repercussions in the brain. In fact, if the traumatic event affecting the lamina cribrosa is considerable, the latter can break so that some bone fragments penetrate the nearby meningeal layers, breaking them and causing the escape of cerebrospinal fluid . With the escape of a part of the cerebrospinal fluid and the damage of the meninges, the risk of meningitis, encephalitis and / or brain abscess increases .

For a better understanding of nasal bone fractures, readers can consult the article on the broken nose.

NOSE DEFORMATIONS

The most known and common deformation of the nose structures is the deviation of the nasal septum .

The deviation of the nasal septum is a condition that may be present from birth or that may appear following a traumatic event.

In some cases it is asymptomatic, so that the person concerned ignores its presence; in other situations, on the other hand, it causes various disorders, including: obstruction of one or both nostrils, epistaxis, facial pain, respiratory problems in sleep, dry mouth and a sense of pressure in one or both nostrils.

The only way to correct a deviation of the nasal septum is through surgery, known as septoplasty .

The use of septoplasty is foreseen only when the deviation of the nasal septum involves symptoms and complications, incompatible with a normal life.

For a better knowledge of the deviation of the nasal septum, readers can consult the article related to the deviated nasal septum.

HYPERTROPHY OF TURBINATES

Turbinate hypertrophy is the result of chronic and permanent swelling of the turbinate eyelid respiratory mucosa. This swelling involves a reduction in the space available for normal nasal breathing, so those suffering from turbinate hypertrophy develop symptoms such as: